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Promoted charge separation and specific surface area via interlacing of N-doped titanium dioxide nanotubes on carbon nitride nanosheets for photocatalytic degradation of Rhodamine B

  • Jong-Hoon Lee , Seong-Jun Mun , Seul-Yi Lee EMAIL logo and Soo-Jin Park EMAIL logo
Published/Copyright: April 11, 2022
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Nanotechnology Reviews
From the journal Nanotechnology Reviews Volume 11 Issue 1

Abstract

Titanium dioxide (TiO2) has been regarded as a promising catalyst owing to its superior charge transport properties in photocatalytic degradation of organic pollutants and photocatalytic hydrogen generation. However, a major bottleneck toward the utilization of TiO2 photocatalysts is inefficient exploitation of visible light and low adsorption behavior. To address this issue, we fabricated a hybrid nanocomposite composed of one-dimensional N-doped TiO2 nanotubes (N-TNTs) and two-dimensional graphitic carbon nitride nanosheets (g-CNNs) to improve photocatalytic behavior. Furthermore, photogenerated electron–hole pairs in the hybrid N-TNT/g-CNN composites were efficiently separated by introducing g-CNNs. In addition, the improved specific surface area provided many active sites, resulting in higher photocatalytic reactions in kinetics. Based on these features, the Rhodamine B photocatalytic degradation efficiency was the highest, ∼85%, under solar-light irradiation in the N-TNT/g-CNN composites (7 wt% of the g-CNN content), which is two times higher than that of the N-TNT. Moreover, excellent durability and stability were observed after four cycles, which can be attributed to the extended optical absorption range and enhanced separation of the photogenerated electron–hole pairs.

Graphical abstract

Keywords: photocatalysts; nitrogen doping; TiO2 nanotubes; graphitic carbon nitride; nanocomposites

1 Introduction

Rapid industrialization and population growth have accelerated environmental issues, such as abnormal climate change, global warming, and water pollution. In particular, discharge of toxic and harmful wastewater has deteriorated the water-deficit issue and water quality, which affects human health and the environment [1–3].

Photocatalytic purification using semiconductor-based photocatalysis technology has attracted considerable attention due to its great potential for degradation of organic pollutants [4–6]. Titanium dioxide (TiO2) is a well-known photocatalytic material because of its excellent chemical stability, high photocatalytic activity, noncorrosive property, and low cost [7–11]. Furthermore, its oxidizing capability is sufficient to decompose substances. Therefore, it is environmentally friendly [12,13]. However, the main drawbacks of TiO2 are low absorption efficiency of sunlight due to its large bandgap (∼3.2 eV) and low quantum production efficiency, resulting in a high recombination rate of photogenerated electron–hole pairs [14–16]. To date, many methods have been proposed for improving photocatalytic activities of TiO2-based semiconductors, such as heteroatom doping, to achieve better separation of photogenerated electron–electron pairs. Nonmetal atom doping is an effective strategy for enhancing the photocatalytic efficiency by adjusting the electronic structure and promoting the reaction surface [17–21]. Doping of nonmetallic elements (C, N, O, and S) results in enhanced photocatalytic performance due to the reduction in the recombination rate of the photogenic electron–hole pairs with an extended range of light absorption and charge transfer efficiency [22]. In particular, the electron–hole pair recombination rate is effectively suppressed in N-doped TiO2 nanocomposites because the ion radius of nitrogen is close to that of oxygen [23–25]. Furthermore, one-dimensional (1D)-nanostructured TiO2 nanotubes (TNTs) as a type of TiO2 nanomaterial have shown superior photocatalytic activity [26–28]. TNTs are more suitable for various practical applications due to their higher electron mobility, large specific surface area, and high adsorption capacity than other-dimensional TiO2 materials [29].

tRecently, graphitic carbon nitride nanosheets (g-CNNs) have been considered as one of the most promising two-dimensional (2D) nonmetallic materials for photocatalytic activity because of their low cost, environmental friendliness, high corrosion resistance, and a narrow bandgap of 2.7 eV [30–32]. The g-CNNs exhibit remarkable ability to absorb visible light (380–460 nm) and high chemical stability in acidic and basic aqueous solutions under solar-light irradiation due to their strong covalent bonds [33,34]. However, the high recombination rate of the photogenerated electron–hole pairs and low oxidation ability of organic species owing to low oxidation potential have restricted the degradation of organic pollutants for water purification applications [35,36].

A nanoarchitecture achieved by hybridizing 1D TNTs and g-CNNs may provide a highly efficient approach to improve the visible-light photocatalytic properties [37–39]. The excited electrons on the conduction band of the g-CNNs can migrate to the TiO2 surfaces through the nanoarchitecture pathway because the conduction band of the g-CNNs (−1.10 eV vs. normal hydrogen electrode (NHE)) is more negative than that of TiO2 (−0.29 eV vs. NHE) [40,41]. This leads to the suppression of the recombination of photogenerated electron–hole pairs to enhance their separation efficiency [42,43].

Herein, we designed hybrid nanocomposites composed of N-doped TNT (N-TNT)-interlaced g-CNNs via a hydrothermal process. The morphological, structural, and textural properties were studied systematically using transmission electron microscopy (TEM), X-ray diffraction (XRD), and a N2/77K adsorption–desorption analysis, respectively. The surface chemical compositions were characterized by X-ray photoelectron spectroscopy (XPS). The photocatalytic performances were evaluated through UV-Vis diffuse reflectance spectroscopy (UV/DRS) measurements and photoluminescence analysis. In particular, the photodegradation efficiency for the removal of Rhodamine B (RhB) was evaluated under solar irradiation. Based on our experimental results, the synergistic effect between two components of the hybrid N-TNT/g-CNN composites and the possible degradation mechanisms for enhanced photocatalytic behaviors have been discussed.

2 Experimental

2.1 Materials and chemicals

Commercially available TiO2 nanopowder (P25; Degussa Co.), hydrochloric acid (HCl: 37%; Degussa Co.), urea (CH4N2O: 99%; OCI Co.), sodium hydroxide (NaOH: 99%; Sigma-Aldrich Co.), and melamine (C3H6N6: 99%; Sigma-Aldrich Co.) were purchased and used as received without any further purification.

2.2 Synthesis of the hybrid N-TNT/g-CNN composites

N-TNTs were prepared using a hydrothermal synthesis process with some modification, based on the previous reports [44,45]. For the N-TNT preparation, 1.5 g of P25 and 1.9 g of urea were dispersed in 50 mL of 10 M NaOH solution and stirred for 1 h. The solution was transferred to a Teflon-lined stainless steel vessel and heated with a ramp temperature of 5°C/min to 110°C, which was subsequently maintained for 24 h for the hydrothermal condition. The resulting suspension was washed with 0.1 N HCl and deionized (DI) water until pH < 7 was obtained. It was then dried at 90°C in a conventional oven to obtain needle-shaped N-TNTs as the product. The N-TNT product was calcined at 400°C for 2 h, which mainly composed the anatase phase.

For the synthesis of g-CNNs, 2 g of melamine was calcined with a ramp temperature of 5°C/min to 500°C and maintained for 4 h in an alumina crucible to obtain a pale-yellow product of bulk-graphitic carbon nitride (g-CN). The bulk product was transferred into 50 mL of DI water and subsequently exfoliated using ultrasonication. The exfoliated CNN was obtained by centrifuging at 4,000 rpm for 10 min and dried at 90°C in air for 24 h.

The N-TNT/g-CNN composites were prepared via hydrothermal synthesis. A mixture of synthesized N-TNTs and g-CNNs prepared with different fractions of g-CNNs was ultrasonicated in DI water for 30 min, then sealed in a Teflon-lined stainless steel vessel, and kept at 160°C for 12 h. The mixture was then filtered and dried in a vacuum oven at 90°C for 12 h. The resulting powder is referred to as “N-TNT/g-CNNs-x,” where x denotes the wt% of the added fraction of g-CNNs. The preparation process for the N-TNT/g-CNN composites is shown in Scheme 1.

Scheme 1 Schematic illustrations for the preparation of the N-TNT, g-CNNs, and hybrid N-TNT/g-CNN nanocomposites.
Scheme 1

Schematic illustrations for the preparation of the N-TNT, g-CNNs, and hybrid N-TNT/g-CNN nanocomposites.

2.3 Characterization

The crystalline structures were investigated by XRD (D2 PHASER; Bruker Co.) analysis at Cu Kα radiation, 30 kV, and 10 mA (λ = 1.5406 Å) with a 0.6 mm grating. The morphological information was obtained using field-emission TEM (JEM2100F; JEOL). The chemical state and composition were evaluated using XPS (K-Alpha; Thermo Fisher Scientific Co.). Photoluminescence (PL; Ram Boss, Dongwoo Optron Co. Ltd.) measurements were performed using a He–Cd laser with a 325 nm excitation wavelength. The N2 adsorption–desorption isotherms were recorded at 77 K using a BELSORP Max instrument (BEL Japan, Inc.). The specific surface area (S BET) and pore size distribution were determined using the Brunauer–Emmett–Teller (BET) equation and non-local density functional theory (NLDFT), respectively. The UV-Vis/diffuse reflection spectra were obtained on a UV-Vis spectrophotometer (Hitachi U-3010) with a diffuse reflector, and the bandgaps were determined using the Kubelka–Munk model. The electrochemical impedance spectroscopy (EIS) measurement was performed in the frequency range from 100 kHz to 0.01 Hz with an amplitude of 5 mV using IviumStat (Ivium Technologies, B.V.).

2.4 Photocatalytic performance

The photocatalytic activities of the hybrid N-TNT/g-CNN composites were evaluated using an aqueous solution of Rh B (>95%; Sigma-Aldrich Co.) as a contaminant in a sealed quartz reaction vessel. Then, 0.02 g of the synthesized catalyst was dispersed in 50 mL of Rh B (10 ppm) for the photocatalytic experiment. The mixture was stirred for 30 min in the dark to reach the absorption–desorption equilibrium. The photocatalytic performance was determined by applying a Xe full-spectrum solar simulator (Sun 2000, ABET) as a light source with an irradiation intensity of 200 W/m2 to induce photocatalytic degradation. Each experimental set was monitored for 2 h by recording the absorption band at 555 nm every 15 min. The used catalyst was collected by centrifugation and washed with water to evaluate the stability of the prepared catalyst through its reusability in cycle testing.

3 Results and discussion

The schematic illustrations of the preparation for the N-TNT, g-CNNs, and hybrid N-TNT/g-CNN nanocomposites are shown in Scheme 1. Then, g-CN was directly synthesized by the efficient formation of tri-s-triazine units resulting from sublimation pyrolysis of melamine powder at atmospheric pressure in air. Subsequently, g-CN was exfoliated by a mechanical process to obtain the individual nanosheets. N-TNTs were prepared using P25 and urea in an alkaline-based hydrothermal synthesis. The hybrid N-TNT/g-CNN composites were successfully synthesized via a facile hydrothermal treatment as a function of the adding fraction of the g-CNNs.

3.1 Morphological/structural/textural properties

TEM was used to study the morphology of the samples obtained in the study. Typical 1D morphologies of the synthesized N-TNT are shown in Figure 1(a). The diameter and length of the N-TNT are estimated to be approximately 8 nm and several hundred nanometers, respectively. The walls of the N-TNT forming the bundles can also be observed. The TEM image of the g-CNNs shows obvious 2D graphene-like sheet structures with smooth surfaces (Figure 1(b)). Figure 1(c) shows the corresponding TEM image for the hybrid N-TNT/g-CNN composites, and it can be clearly observed that a number of 1D tubular structures of the N-TNT are homogeneously interfaced with the 2D g-CNNs without destroying the intrinsic structure of both the T-TNT and g-CNNs. Interestingly, it was assumed that the 2D g-CNN framework was restricted when it was in contact with the N-TNT, indicating an attractive effect on the impediment for restacking of the g-CNNs in the hybrid composites. The selected area electron diffraction (SAED) patterns of the N-TNT/g-CNNs exhibit lattice spacings for the (101), (004), (200), (105), (211), and (204) planes of the TiO2 anatase phase [46]. This indicates that the anatase N-TNT is randomly well-adhered onto the g-CNN surfaces by amorphous carbon substances. The presence of the amorphous carbon phase in the g-CNNs plays an important role in conglutinating with TiO2, resulting in the improvement of the thermal stability and crystallinity of TiO2 [47,48].

Figure 1 TEM images of (a) N-TNT, (b) g-CNNs, and (c) N-TNT/g-CNNs-7 (inset: SAED patterns); (d) XRD patterns; and (e) N2/77 K adsorption–desorption isotherms and their pore size distributions (inset) of the samples studied in this work.
Figure 1

TEM images of (a) N-TNT, (b) g-CNNs, and (c) N-TNT/g-CNNs-7 (inset: SAED patterns); (d) XRD patterns; and (e) N2/77 K adsorption–desorption isotherms and their pore size distributions (inset) of the samples studied in this work.

The crystalline structure of the N-TNT, g-CNNs, and hybrid N-TNT/g-CNN composites can be assessed based on the XRD patterns, as shown in Figure 1(d). The XRD pattern of the g-CNNs shows two distinct peaks at 12.5° (100) and 27.3° (002), which are associated with the in-planar trigonal N linkage of the tri-s-triazine units and the periodic inter-planar stacking of the conjugated aromatic systems, respectively, of graphitic carbon nitride (JCPDS no. 87-1526) [49,50]. The appearance of these peaks confirmed the successful formation of the g-CNNs. The characteristic diffraction peaks of the N-TNT were observed at 2θ = 25.3°, 37° 48°, 53°, 55°, and 63° and can be attributed to (101), (004), (200), (105), (211), and (204) of the TiO2 crystal planes, respectively. Most of the diffraction reflections originate from P25. Those unique peaks correspond to the anatase structure of TiO2 (JCPDS no. 21-1272) [25,44]. For the hybrid N-TNT/g-CNN composites, we found that most diffraction peaks were identical to those of N-TNT, indicating that the anatase structures were maintained during the hydrothermal process. Moreover, the newly appeared small peak at approximately 27° for the hybrid N-TNT/g-CNN composites was associated with the (002) plane due to the introduction of the g-CNNs. It was confirmed that the intensities of the peaks gradually increased with increasing loading fraction of the g-CNNs (Figure S1). The peak at 12.5° disappeared mainly due to the fact that the introduction of the N-TNT onto the g-CNN surfaces, in particular, affects the in-planar trigonal N, which may decrease the ordering degree of the in-planar structures. These results are suggestive of the successful formation of the hybrid N-TNT/g-CNN composites via a simple hydrothermal process, as previously confirmed in the TEM measurements.

To investigate the textural properties, the N2 adsorption–desorption isotherms were obtained, as shown in Figure 1(e) and Figure S2. The specific surface areas (S BET) and pore volumes are summarized in Table 1. The S BET and total pore volume of the N-TNT were 203 m2/g and 0.601 cm3/g, respectively, while those of P25 were 74 m2/g and 0.150 cm3/g. The adsorption–desorption isotherm of the N-TNT exhibited a type IV isotherm with hysteresis loop type III characteristics according to the IUPAC classifications, which is attributable to the 1D tubular structure of TiO2 that is mainly composed of mesopores. The g-CNN sample showed a type IV isotherm, and the S BET value of the g-CNNs was 51 m2/g, which is similar to that reported in other studies [51,52]. The S BET and the porosity of the N-TNT/g-CNN composites increased with increasing fraction of the g-CNNs up to 7% by weight; however, it decreased sharply in the N-TNT/g-CNNs-10. They exhibited typical H2-type hysteresis loops, which represent complex pore structures by the hybridization of two components. These results clearly indicate that the introduction of excessive g-CNNs could interfere with the establishment of an efficient pore structure in the hybrid N-TNT/g-CNN composites. Importantly, the high S BET and well-developed pore structure can provide more active sites for a faster mass transfer to target contaminants and increase light absorption capacity during the photocatalytic reaction.

Table 1

Textural parameters of the samples studied in this work

Specimen S BET a (m2/g) V total b (cm3/g) V meso c (cm3/g) V micro d (cm3/g) D P e (nm)
P25 74 0.150 0.109 0.109 4.7
g-CNNs 51 0.430 0.276 0.154 19.8
N-TNT 203 0.601 0.514 0.087 6.3
N-TNT/g-CNNs-1 101 0.318 0.282 0.036 9.0
N-TNT/g-CNNs-3 114 0.326 0.289 0.037 7.8
N-TNT/g-CNNs-5 120 0.335 0.312 0.023 8.4
N-TNT/g-CNNs-7 126 0.370 0.332 0.038 7.7
N-TNT/g-CNNs-10 94 0.203 0.179 0.024 9.7

a S BET: specific surface area computed using the BET equation at a relative pressure range of 0.001–0.01. b V total: total pore volume determined from the NLDFT method. c V meso: mesopore (2–50 nm) volume determined using the NLDFT method. d V micro: micropore (<2 nm) volume determined using the NLDFT method. e D P: average mesopore diameter calculated using the NLDFT method.

3.2 Chemical properties

The chemical compositions of the surface elements and their chemical configurations after the hybridization of the N-TNT and g-CNNs were analyzed using XPS, as shown in Figure 2. The XPS survey spectra confirmed that both the N-TNT and the hybrid N-TNT/g-CNN composites are mainly composed of C, O, N, and Ti elements. The significant increase in the C and N contents in the N-TNT/g-CNNs was clearly due to the introduction of the CNN. As shown in Figure 2(b), the two peaks of Ti2p3/2 and Ti2p1/2 in the XPS spectrum can be attributed to the Ti4 + species in TiO2 of the hybrid N-TNT/g-CNNs-7, and they shifted at approximately 0.7 eV toward lower binding energy compared to those of the N-TNT. This shift indicates that the chemical bond between the N-TNT and g-CNNs possibly occurred rather than physical interactions.

Figure 2 XPS results: (a) full spectra of N-TNT and N-TNT/g-CNNs-7, (b) Ti2p spectra of N-TNT and N-TNT/g-CNNs-7, (c) C1s and (d) N1s spectra of N-TNT, and (e) C1s and (f) N1s spectra of N-TNT/g-CNNs-7.
Figure 2

XPS results: (a) full spectra of N-TNT and N-TNT/g-CNNs-7, (b) Ti2p spectra of N-TNT and N-TNT/g-CNNs-7, (c) C1s and (d) N1s spectra of N-TNT, and (e) C1s and (f) N1s spectra of N-TNT/g-CNNs-7.

To further explore a synergetic effect between the two components, we de-convoluted the high-resolution core-level spectra of C1s, N1s, and O1s of the hybrid N-TNT/g-CNN composites, as presented in Figure 2(c–f) and Figure S3. The C1s spectra were de-convoluted into three segments at 285.1, 286.1, and 288.7 eV coinciding with the C–C and C═C bonds obtained from the graphite structure or amorphous carbon, the sp2 carbon atom bonded to N inside the aromatic unit, and the N–C═N group (Figure 2(c and e)), respectively. These agree with the values reported in the literature [53,54]. The distinct peaks at 286.1 and 288.7 eV in the N-TNT/g-CNN composites are suggestive of the development of a variety of functional groups on the surfaces, which could be beneficial for the dispersion of the composites in the aqueous solution.

Figure 2(d) shows the high-resolution N1s spectrum for the N-TNT that reveals a single peak appearing at 401.4 eV. The N1s binding energy of 401.4 eV can be assigned to the amino moieties derived from the melamine pyrolysis during the synthesis process. For the N-TNT/g-CNN composites, the newly emerging peaks pertaining to N1s at 398.8 and 399.3 eV can be assigned to the sp2-hybridized N (C═N–C) involved in the triazine rings and tertiary N in the N–(C)3 groups, respectively [55,56]. This can be attributed to the introduction of the g-CNNs and/or a newly established interaction between the N-TNT and g-CNNs in the hybrid composites. This can improve the chemical stability of the composites, facilitating fast electron transport between the two components [57].

We can obtain additional information on the behaviors of oxygen functionalities by examining the high-resolution O1s spectra of the N-TNT and N-TNT/g-CNNs. The peaks at 530.6 eV are associated with the Ti–O bond in the N-TNT. After the introduction of the CNN, the increase in the peak at 532.7 eV and a small shift to the higher binding energy in the N-TNT/g-CNNs are observed, as shown in Figure S3. These led to an increase in the electron density of the Ti phase, indicating that some oxygen molecules in Ti–O are partially substituted with Ti–N [58].

Figure 3(a) and Figure S4 show UV-Vis/DRS spectra of the samples in the study. It can be clearly seen that the absorption of the hybrid T-TNT/g-CNN composites was greatly enhanced in the visible-light region from 350 to 700 nm compared to the N-TNT and g-CNNs, when each of them is a singular component [59–61]. The absorption edge of the N-TNT/g-CNNs remarkably shifts toward longer wavelengths, which indicates that it is very active in the visible-light region. The enhanced visible-light response indicates improved visible-light-harvesting capability for highly efficient performance on solar-light irradiation. In addition, we found that the absorption behaviors in the visible-light region enhanced as the fraction of the g-CNNs increased (Figure S4). These results clearly indicate that the presence of the g-CNNs in the hybrid composites facilitates the optical reaction of the TiO2-based catalyst in a higher visible spectral range, which demonstrates the applicability of the hybrid N-TNT/g-CNN composites as solar-light photocatalysts, which are efficient on the visible region also. Figure 3(b) shows the plots obtained from the Kubelka–Munk model in each spectrum [62]. The Kubelka–Munk equation is as follows:

(1) α = ( 1 − R ) 2 2 R ,

where α is the Kubelka–Munk function, R is the decimal fraction of the reflectance of the colored sample, and hν is the electromagnetic wave energy.

Figure 3 (a) UV-Vis/DRS spectra and (b) plots of the Kubelka–Munk remission function corresponding to the spectra of the prepared samples.
Figure 3

(a) UV-Vis/DRS spectra and (b) plots of the Kubelka–Munk remission function corresponding to the spectra of the prepared samples.

A summary of the optical properties is also listed in Table 2. The bandgap energies determined by the Kubelka–Munk equation are 3.15, 3.09, 2.60, and 2.81 eV for P25, the N-TNT, the g-CNNs, and the N-TNT/g-CNNs-7, respectively. For the N-TNT/g-CNN composites, it is revealed that the bandgap gradually decreased from 3.02 to 2.81 eV with increasing loading fraction of the g-CNNs, and it slightly increased in the N-TNT/g-CNNs-10 sample. This enhanced red-shift of the optical bandgap in the hybrid composites might be related to the interaction between the N-TNT and g-CNNs, acting as an electron container to trap the electrons emitted from the N-TNT by solar-light irradiation, thereby hindering electron–hole pair recombination [57,63]. This effect clearly indicates that the g-CNNs play a key role in the enhancement of the photocatalytic activity of the N-TNT. The experimentally measured bandgap energies represent similar values, as shown in Figure S5 [64,65].

Table 2

Summary of the physicochemical properties of the prepared samples

Specimen F a (wt%) E g b (eV) Efficiency of degradationc (%) R d (min−1) R 2 e
P25 0 3.15 14.6 0.112 × 10−2 0.9623
N-TNT 0 3.09 42.0 0.389 × 10−2 0.9717
g-CNNs 100 2.60 — — —
N-TNT/g-CNNs-1 1 3.02 53.5 0.521 × 10−2 0.9819
N-TNT/g-CNNs-3 3 2.98 61.2 0.617 × 10−2 0.9747
N-TNT/g-CNNs-5 5 2.92 71.5 0.764 × 10−2 0.9667
N-TNT/g-CNNs-7 7 2.81 84.3 1.178 × 10−2 0.9797
N-TNT/g-CNNs-10 10 2.85 55.9 0.557 × 10−2 0.9894

a F: a percentage of the introduced g-CNNs by weight. b E g: bandgap of samples calculated using the Kubelka–Munk equation. cPercentage of degradation: degradation efficiency of RhB after 120 min. dRate constants: rate constants (k) estimated by the slope of pseudo-first-order kinetics equation. e R 2: correlation coefficient of pseudo-first-order fitted graph.

We performed PL spectroscopy to verify the interfacial charge transfer and separation efficiency of the photogenerated charge carrier over the photocatalysts studied in this work. The intensity in the PL spectra indicates the recombination of the photogenerated electron–hole pairs [66]. The PL spectra of the N-TNT, g-CNNs, and hybrid N-TNT/g-CNNs-7 are shown in Figure 4. The PL spectrum of the g-CNNs showed the strongest emission peak at approximately 460 nm, while the N-TNT was non-fluorescent, which is in good agreement with the analysis of the UV-Vis absorption spectra. This non-fluorescent behavior of N-TNT demonstrates a completely separated phenomenon which is hard to electron-and-hole transfer [67,68]. Therefore, N-TNT is inefficient for photocatalytic reaction. The shape of the emission peak for the N-TNT/g-CNNs-7 is similar to that of the g-CNNs, albeit significantly quenched. The PL spectra of all the hybrid N-TNT/g-CNN composites were significantly reduced compared to that of g-CNNs, with increasing loading fraction of the g-CNNs. This indicates that excellent separation of photogenerated electron–hole pairs was achieved by adding the g-CNNs (at maximum 7% by a weight) into the N-TNT, resulting from the significantly suppressed recombination loss and/or rate. This means that a large number of photogenerated charge carriers are present at the N-TNT/g-CNN surfaces, which are favorable for a higher photocatalytic activity, leading to the optimized electron transfer pathway in the N-TNT/g-CNNs under visible-light irradiation [69].

Figure 4 PL spectra of the N-TNT, g-CNNs, and N-TNT/g-CNNs-7.
Figure 4

PL spectra of the N-TNT, g-CNNs, and N-TNT/g-CNNs-7.

EIS was investigated for understanding electrochemical characteristics of as-prepared samples. The N-TNT/g-CNNs-7 represent the smallest radius of the Nyquist semicircle, indicating efficient charge transfer from low resistance (Figure S6). This synergistic effect on effective charge transfer and low resistance attributed to the unique structure of N-TNT-interlaced g-CNN nanocomposites.

3.3 Photodegradation of Rhodamine B

To evaluate the photocatalytic behaviors of the N-TNT/g-CNN composites, the efficiency of RhB photodegradation was measured at an ambient temperature under solar-light irradiation [70–72]. The prepared samples were added to the RhB solution with continuous stirring in the dark for approximately 30 min to achieve an absorption equilibrium between the catalyst and RhB. Figure 5(a) shows that the degradation efficiency of RhB is in the following order: N-TNT/g-CNNs-7 > N-TNT/g-CNNs-5 > N-TNT/g-CNNs-3 > N-TNT/g-CNNs-10 > N-TNT/g-CNNs-1 > N-TNT > P25. As shown initial light off step, effective adsorption RhB from well-designed N-TNT/g-CNNs significantly enhance the photocatalytic performance compared with N-TNT and P25. The RhB degradation efficiency of the hybrid N-TNT/g-CNN composites was found to be in the range of 53.5–84.3% after 120 min of solar-light irradiation (Table 2). The highest efficiency showed 84.3% for the N-TNT/g-CNNs-7 samples, which is two times higher than that of the N-TNTs (42%). The photocatalytic degradation almost completed with 98% efficiency after 150 min (Figure S7). As shown in Figure 5(b), the photolysis of the hybrid N-TNT/g-CNN composites was determined according to the first-order reaction kinetics used to model the concentration change of the organic dye in the reaction time:

(7) ln C t C 0 = − K t ,

where C t and C 0 are the reaction and initial concentrations of RhB, respectively; and K is a rate constant.

Figure 5 (a) Photodegradation of RhB under simulated solar-light irradiation and (b) pseudo-first-order kinetics of photocatalytic reaction for the hybrid N-TNT/g-CNN composites.
Figure 5

(a) Photodegradation of RhB under simulated solar-light irradiation and (b) pseudo-first-order kinetics of photocatalytic reaction for the hybrid N-TNT/g-CNN composites.

Figure 5(b) shows that the regression coefficient rate constants for the RhB degradation are in the following order: N-TNT/g-CNNs-7 > N-TNT/g-CNNs-5 > N-TNT/g-CNNs-3 > N-TNT/g-CNNs-10 > N-TNT/g-CNNs-1 > N-TNT > P25. This indicates that the introduction of the g-CNNs in the TiO2-based catalysts improved photodegradation ability. The g-CNNs play an important role in enhancing the photodegradation efficiency of organic dyes (RhB). The photocatalytic activity of the hybrid N-TNT/g-CNN composites depends on the bandgap and wavelength of the light used for the electron excitation, suggesting that N-TNT/g-CNNs-7 (bandgap: 2.81 eV) with a narrow bandgap is highly effective under solar-light irradiation. However, excess amount of g-CNNs (N-TNT/g-CNNs-10) might impede the efficient charge transfer between two components, which is attributable to the decrease in the accessible active sites at the interfaces. That is, the high content of the g-CNNs in N-TNT/CNNs-10 resulted in the degradation of the photocatalytic performance for the RhB decomposition. Based on our results, we confirmed that the nanoarchitecture composed of 1D N-TNT and 2D CNNs plays an important role as an electric charge carrier recombination center created by the electric field at the interface between the N-TNT and g-CNNs [73]. Furthermore, in the RhB decomposition experiments, four cycles of the recycling test were performed to investigate the durability and reusability of the photocatalysts, as shown in Figure S8. During the fourth cycle, no evident decrease in the photocatalytic activity of samples was noted. The crystalline structure of samples also retained after four cycles (Figure S9). These results indicate that the hybrid photocatalyst designed in the study is very stable with good repeatability.

The spin-trapping electron spin resonance (ESR) was investigated using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as trapping agents for understanding the photocatalytic degradation mechanism. Figure 6 represents the ESR spectra on hydroxyl radical (˙OH)- and superoxide radical ( ˙ O 2 − )-trapped conditions under simulated solar-light irradiation. The characteristics signal of radical species is stronger on N-TNT/g-CNNs-7 compared with other samples representing lower signals, indicating more efficient radical formation over the N-TNT/g-CNNs-7 surface than over the other samples’ surfaces.

Figure 6 Spin-trapping ESR spectra of as-prepared samples using DMPO for (a) hydroxyl radical (˙OH) and (b) superoxide radical (˙O2 −) (under simulated solar-light irradiation).
Figure 6

Spin-trapping ESR spectra of as-prepared samples using DMPO for (a) hydroxyl radical (˙OH) and (b) superoxide radical (˙O2 −) (under simulated solar-light irradiation).

Based on our experimental results, the photocatalyst mechanism of the N-TNT/g-CNN composites is as follows [74]:

(2) TiO 2 + Solar light TiO 2 + ( e CB − + h VB + ) ,

(3) e CB − + O 2 → ˙ O 2 − ,

(4) h VB +   + H 2 O →   ˙ OH + H + ,

(5) h VB +   + OH − →   ˙ OH + H + ,

(6) Organic dye + ˙ O 2 − or ˙ OH → CO 2 + H 2 O .

When the hybrid N-TNT/g-CNN composites are irradiated with solar light, the electron–hole pairs are generated on the g-CNN surfaces, and the generated electrons are transferred from the g-CNNs to TiO2. The photogenerated electrons are injected into the TiO2 conduction band, and their interactions on the TiO2 surface and adsorbed oxygen molecules form superoxide radicals. Simultaneously, H2O molecules around the composite are separated into free OH radicals and hydrogen ions by the reaction of positively charged TiO2 with the adsorbed water. The removal of organic dye is achieved via redox reactions between the formed superoxide radicals and hydroxyl radicals. Thus, the strong redox behaviors in the N-TNT/g-CNNs composites interact with RhB to significantly enhance the photocatalytic behavior and efficiency of the photolysis process. A schematic diagram of the photocatalytic process is presented in Scheme 2 [75–77].

Scheme 2 Schematic illustration of the photocatalytic activity for the hybrid N-TNT/g-CNN composites.
Scheme 2

Schematic illustration of the photocatalytic activity for the hybrid N-TNT/g-CNN composites.

4 Conclusion

In this study, we successfully developed N-TNT-interlaced g-CNN nanocomposites via a facile method. N-TNT/g-CNNs-7 (loading fraction of g-CNNs, 7% by a weight) exhibited 126 m2/g and 0.370 cm3/g of specific surface area and total pore volume, respectively. The degradation efficiency of RhB for N-TNT/g-CNNs-7 was 84.3% under solar-light irradiation as a result of the introduction of CNNs, which is twofold higher than that of the N-TNT. This improvement was owing to the optimized bandgap energy (2.81 eV), leading to a wider absorption light range. In addition, higher photocatalytic reaction kinetics are attributable to the better adsorption behaviors (high surface areas and porosity) and hydrophilic characteristics owing to abundant oxygen-functional groups, resulting in a number of active sites and fast charge transportation on the N-TNT/g-CNN surfaces in an aqueous solution. Thus, these can accelerate the efficient separation of the photogenerated electron–hole pairs and facilitate significant suppression of recombination loss and rate. Based on our experimentally verified results, we believe that these unique nanoarchitecture composed of 1D N-TNT and 2-D g-CNNs provide a novel strategy for significantly improving the photocatalytic performance of the TiO2-based photocatalyst toward visible-light utilization.

tel: +82-32-876-7234

  1. Funding information: This work was supported by Nano- Convergence Foundation (www.nanotech2020.org) funded by the Ministry of  Science  and  ICT  (MSIT,  Korea)  and the Ministry of Trade, Industry and Energy (MOTIE, Korea). (Project Name: Development of high-efficiency activated carbon filter for removing indoor harmful elements [VOCs, radon, bacteria, etc.].) The Technological Innovation R&D Program (S2849653) was funded by the Small and Medium Business Administration (SMBA, Korea).

  2. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  3. Conflict of interest: The authors state no conflict of interest.

  4. Data availability statement: Supplementary data associated with this article can be found, in the online version at the journal website.

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Received: 2021-11-09
Revised: 2022-02-06
Accepted: 2022-02-16
Published Online: 2022-04-11

© 2022 Jong-Hoon Lee et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  17. Enhancement of the mechanical properties of HDPE mineral nanocomposites by filler particles modulation of the matrix plastic/elastic behavior
  18. Effect of plasticizers on the properties of sugar palm nanocellulose/cinnamon essential oil reinforced starch bionanocomposite films
  19. Optimization of nano coating to reduce the thermal deformation of ball screws
  20. Preparation of efficient piezoelectric PVDF–HFP/Ni composite films by high electric field poling
  21. MHD dissipative Casson nanofluid liquid film flow due to an unsteady stretching sheet with radiation influence and slip velocity phenomenon
  22. Effects of nano-SiO2 modification on rubberised mortar and concrete with recycled coarse aggregates
  23. Mechanical and microscopic properties of fiber-reinforced coal gangue-based geopolymer concrete
  24. Effect of morphology and size on the thermodynamic stability of cerium oxide nanoparticles: Experiment and molecular dynamics calculation
  25. Mechanical performance of a CFRP composite reinforced via gelatin-CNTs: A study on fiber interfacial enhancement and matrix enhancement
  26. A practical review over surface modification, nanopatterns, emerging materials, drug delivery systems, and their biophysiochemical properties for dental implants: Recent progresses and advances
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  28. Effects of microalloying elements added by in situ synthesis on the microstructure of WCu composites
  29. A highly sensitive nanobiosensor based on aptamer-conjugated graphene-decorated rhodium nanoparticles for detection of HER2-positive circulating tumor cells
  30. Progressive collapse performance of shear strengthened RC frames by nano CFRP
  31. Core–shell heterostructured composites of carbon nanotubes and imine-linked hyperbranched polymers as metal-free Li-ion anodes
  32. A Galerkin strategy for tri-hybridized mixture in ethylene glycol comprising variable diffusion and thermal conductivity using non-Fourier’s theory
  33. Simple models for tensile modulus of shape memory polymer nanocomposites at ambient temperature
  34. Preparation and morphological studies of tin sulfide nanoparticles and use as efficient photocatalysts for the degradation of rhodamine B and phenol
  35. Polyethyleneimine-impregnated activated carbon nanofiber composited graphene-derived rice husk char for efficient post-combustion CO2 capture
  36. Electrospun nanofibers of Co3O4 nanocrystals encapsulated in cyclized-polyacrylonitrile for lithium storage
  37. Pitting corrosion induced on high-strength high carbon steel wire in high alkaline deaerated chloride electrolyte
  38. Formulation of polymeric nanoparticles loaded sorafenib; evaluation of cytotoxicity, molecular evaluation, and gene expression studies in lung and breast cancer cell lines
  39. Engineered nanocomposites in asphalt binders
  40. Influence of loading voltage, domain ratio, and additional load on the actuation of dielectric elastomer
  41. Thermally induced hex-graphene transitions in 2D carbon crystals
  42. The surface modification effect on the interfacial properties of glass fiber-reinforced epoxy: A molecular dynamics study
  43. Molecular dynamics study of deformation mechanism of interfacial microzone of Cu/Al2Cu/Al composites under tension
  44. Nanocolloid simulators of luminescent solar concentrator photovoltaic windows
  45. Compressive strength and anti-chloride ion penetration assessment of geopolymer mortar merging PVA fiber and nano-SiO2 using RBF–BP composite neural network
  46. Effect of 3-mercapto-1-propane sulfonate sulfonic acid and polyvinylpyrrolidone on the growth of cobalt pillar by electrodeposition
  47. Dynamics of convective slippery constraints on hybrid radiative Sutterby nanofluid flow by Galerkin finite element simulation
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  49. Microstructure-dependent photoelectrocatalytic activity of heterogeneous ZnO–ZnS nanosheets
  50. Cytotoxic and pro-inflammatory effects of molybdenum and tungsten disulphide on human bronchial cells
  51. Improving recycled aggregate concrete by compression casting and nano-silica
  52. Chemically reactive Maxwell nanoliquid flow by a stretching surface in the frames of Newtonian heating, nonlinear convection and radiative flux: Nanopolymer flow processing simulation
  53. Nonlinear dynamic and crack behaviors of carbon nanotubes-reinforced composites with various geometries
  54. Biosynthesis of copper oxide nanoparticles and its therapeutic efficacy against colon cancer
  55. Synthesis and characterization of smart stimuli-responsive herbal drug-encapsulated nanoniosome particles for efficient treatment of breast cancer
  56. Homotopic simulation for heat transport phenomenon of the Burgers nanofluids flow over a stretching cylinder with thermal convective and zero mass flux conditions
  57. Incorporation of copper and strontium ions in TiO2 nanotubes via dopamine to enhance hemocompatibility and cytocompatibility
  58. Mechanical, thermal, and barrier properties of starch films incorporated with chitosan nanoparticles
  59. Mechanical properties and microstructure of nano-strengthened recycled aggregate concrete
  60. Glucose-responsive nanogels efficiently maintain the stability and activity of therapeutic enzymes
  61. Tunning matrix rheology and mechanical performance of ultra-high performance concrete using cellulose nanofibers
  62. Flexible MXene/copper/cellulose nanofiber heat spreader films with enhanced thermal conductivity
  63. Promoted charge separation and specific surface area via interlacing of N-doped titanium dioxide nanotubes on carbon nitride nanosheets for photocatalytic degradation of Rhodamine B
  64. Elucidating the role of silicon dioxide and titanium dioxide nanoparticles in mitigating the disease of the eggplant caused by Phomopsis vexans, Ralstonia solanacearum, and root-knot nematode Meloidogyne incognita
  65. An implication of magnetic dipole in Carreau Yasuda liquid influenced by engine oil using ternary hybrid nanomaterial
  66. Robust synthesis of a composite phase of copper vanadium oxide with enhanced performance for durable aqueous Zn-ion batteries
  67. Tunning self-assembled phases of bovine serum albumin via hydrothermal process to synthesize novel functional hydrogel for skin protection against UVB
  68. A comparative experimental study on damping properties of epoxy nanocomposite beams reinforced with carbon nanotubes and graphene nanoplatelets
  69. Lightweight and hydrophobic Ni/GO/PVA composite aerogels for ultrahigh performance electromagnetic interference shielding
  70. Research on the auxetic behavior and mechanical properties of periodically rotating graphene nanostructures
  71. Repairing performances of novel cement mortar modified with graphene oxide and polyacrylate polymer
  72. Closed-loop recycling and fabrication of hydrophilic CNT films with high performance
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  75. PVDF green nanofibers as potential carriers for improving self-healing and mechanical properties of carbon fiber/epoxy prepregs
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  78. Preparation and bonding mechanisms of polymer/metal hybrid composite by nano molding technology
  79. Damage self-sensing and strain monitoring of glass-reinforced epoxy composite impregnated with graphene nanoplatelet and multiwalled carbon nanotubes
  80. Thermal analysis characterisation of solar-powered ship using Oldroyd hybrid nanofluids in parabolic trough solar collector: An optimal thermal application
  81. Pyrene-functionalized halloysite nanotubes for simultaneously detecting and separating Hg(ii) in aqueous media: A comprehensive comparison on interparticle and intraparticle excimers
  82. Fabrication of self-assembly CNT flexible film and its piezoresistive sensing behaviors
  83. Thermal valuation and entropy inspection of second-grade nanoscale fluid flow over a stretching surface by applying Koo–Kleinstreuer–Li relation
  84. Mechanical properties and microstructure of nano-SiO2 and basalt-fiber-reinforced recycled aggregate concrete
  85. Characterization and tribology performance of polyaniline-coated nanodiamond lubricant additives
  86. Combined impact of Marangoni convection and thermophoretic particle deposition on chemically reactive transport of nanofluid flow over a stretching surface
  87. Spark plasma extrusion of binder free hydroxyapatite powder
  88. An investigation on thermo-mechanical performance of graphene-oxide-reinforced shape memory polymer
  89. Effect of nanoadditives on the novel leather fiber/recycled poly(ethylene-vinyl-acetate) polymer composites for multifunctional applications: Fabrication, characterizations, and multiobjective optimization using central composite design
  90. Design selection for a hemispherical dimple core sandwich panel using hybrid multi-criteria decision-making methods
  91. Improving tensile strength and impact toughness of plasticized poly(lactic acid) biocomposites by incorporating nanofibrillated cellulose
  92. Green synthesis of spinel copper ferrite (CuFe2O4) nanoparticles and their toxicity
  93. The effect of TaC and NbC hybrid and mono-nanoparticles on AA2024 nanocomposites: Microstructure, strengthening, and artificial aging
  94. Excited-state geometry relaxation of pyrene-modified cellulose nanocrystals under UV-light excitation for detecting Fe3+
  95. Effect of CNTs and MEA on the creep of face-slab concrete at an early age
  96. Effect of deformation conditions on compression phase transformation of AZ31
  97. Application of MXene as a new generation of highly conductive coating materials for electromembrane-surrounded solid-phase microextraction
  98. A comparative study of the elasto-plastic properties for ceramic nanocomposites filled by graphene or graphene oxide nanoplates
  99. Encapsulation strategies for improving the biological behavior of CdS@ZIF-8 nanocomposites
  100. Biosynthesis of ZnO NPs from pumpkin seeds’ extract and elucidation of its anticancer potential against breast cancer
  101. Preliminary trials of the gold nanoparticles conjugated chrysin: An assessment of anti-oxidant, anti-microbial, and in vitro cytotoxic activities of a nanoformulated flavonoid
  102. Effect of micron-scale pores increased by nano-SiO2 sol modification on the strength of cement mortar
  103. Fractional simulations for thermal flow of hybrid nanofluid with aluminum oxide and titanium oxide nanoparticles with water and blood base fluids
  104. The effect of graphene nano-powder on the viscosity of water: An experimental study and artificial neural network modeling
  105. Development of a novel heat- and shear-resistant nano-silica gelling agent
  106. Characterization, biocompatibility and in vivo of nominal MnO2-containing wollastonite glass-ceramic
  107. Entropy production simulation of second-grade magnetic nanomaterials flowing across an expanding surface with viscidness dissipative flux
  108. Enhancement in structural, morphological, and optical properties of copper oxide for optoelectronic device applications
  109. Aptamer-functionalized chitosan-coated gold nanoparticle complex as a suitable targeted drug carrier for improved breast cancer treatment
  110. Performance and overall evaluation of nano-alumina-modified asphalt mixture
  111. Analysis of pure nanofluid (GO/engine oil) and hybrid nanofluid (GO–Fe3O4/engine oil): Novel thermal and magnetic features
  112. Synthesis of Ag@AgCl modified anatase/rutile/brookite mixed phase TiO2 and their photocatalytic property
  113. Mechanisms and influential variables on the abrasion resistance hydraulic concrete
  114. Synergistic reinforcement mechanism of basalt fiber/cellulose nanocrystals/polypropylene composites
  115. Achieving excellent oxidation resistance and mechanical properties of TiB2–B4C/carbon aerogel composites by quick-gelation and mechanical mixing
  116. Microwave-assisted sol–gel template-free synthesis and characterization of silica nanoparticles obtained from South African coal fly ash
  117. Pulsed laser-assisted synthesis of nano nickel(ii) oxide-anchored graphitic carbon nitride: Characterizations and their potential antibacterial/anti-biofilm applications
  118. Effects of nano-ZrSi2 on thermal stability of phenolic resin and thermal reusability of quartz–phenolic composites
  119. Benzaldehyde derivatives on tin electroplating as corrosion resistance for fabricating copper circuit
  120. Mechanical and heat transfer properties of 4D-printed shape memory graphene oxide/epoxy acrylate composites
  121. Coupling the vanadium-induced amorphous/crystalline NiFe2O4 with phosphide heterojunction toward active oxygen evolution reaction catalysts
  122. Graphene-oxide-reinforced cement composites mechanical and microstructural characteristics at elevated temperatures
  123. Gray correlation analysis of factors influencing compressive strength and durability of nano-SiO2 and PVA fiber reinforced geopolymer mortar
  124. Preparation of layered gradient Cu–Cr–Ti alloy with excellent mechanical properties, thermal stability, and electrical conductivity
  125. Recovery of Cr from chrome-containing leather wastes to develop aluminum-based composite material along with Al2O3 ceramic particles: An ingenious approach
  126. Mechanisms of the improved stiffness of flexible polymers under impact loading
  127. Anticancer potential of gold nanoparticles (AuNPs) using a battery of in vitro tests
  128. Review Articles
  129. Proposed approaches for coronaviruses elimination from wastewater: Membrane techniques and nanotechnology solutions
  130. Application of Pickering emulsion in oil drilling and production
  131. The contribution of microfluidics to the fight against tuberculosis
  132. Graphene-based biosensors for disease theranostics: Development, applications, and recent advancements
  133. Synthesis and encapsulation of iron oxide nanorods for application in magnetic hyperthermia and photothermal therapy
  134. Contemporary nano-architectured drugs and leads for ανβ3 integrin-based chemotherapy: Rationale and retrospect
  135. State-of-the-art review of fabrication, application, and mechanical properties of functionally graded porous nanocomposite materials
  136. Insights on magnetic spinel ferrites for targeted drug delivery and hyperthermia applications
  137. A review on heterogeneous oxidation of acetaminophen based on micro and nanoparticles catalyzed by different activators
  138. Early diagnosis of lung cancer using magnetic nanoparticles-integrated systems
  139. Advances in ZnO: Manipulation of defects for enhancing their technological potentials
  140. Efficacious nanomedicine track toward combating COVID-19
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  143. Two-dimensional nanomaterial-based polymer composites: Fundamentals and applications
  144. Recent progress and challenges in plasmonic nanomaterials
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  146. Electronic noses based on metal oxide nanowires: A review
  147. Framework materials for supercapacitors
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  152. Recent advances in the preparation of PVDF-based piezoelectric materials
  153. Recent developments in tensile properties of friction welding of carbon fiber-reinforced composite: A review
  154. Comprehensive review of the properties of fly ash-based geopolymer with additive of nano-SiO2
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  156. Graphene-based nanocomposite using new modeling molecular dynamic simulations for proposed neutralizing mechanism and real-time sensing of COVID-19
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  158. Recent developments and future perspectives of biorenewable nanocomposites for advanced applications
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  160. 3D printing customized design of human bone tissue implant and its application
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  163. Nanotechnology interventions as a putative tool for the treatment of dental afflictions
  164. Recent advancements in metal–organic frameworks integrating quantum dots (QDs@MOF) and their potential applications
  165. A focused review of short electrospun nanofiber preparation techniques for composite reinforcement
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  169. Molecular dynamics application of cocrystal energetic materials: A review
  170. Synthesis and application of nanometer hydroxyapatite in biomedicine
  171. Cutting-edge development in waste-recycled nanomaterials for energy storage and conversion applications
  172. Biological applications of ternary quantum dots: A review
  173. Nanotherapeutics for hydrogen sulfide-involved treatment: An emerging approach for cancer therapy
  174. Application of antibacterial nanoparticles in orthodontic materials
  175. Effect of natural-based biological hydrogels combined with growth factors on skin wound healing
  176. Nanozymes – A route to overcome microbial resistance: A viewpoint
  177. Recent developments and applications of smart nanoparticles in biomedicine
  178. Contemporary review on carbon nanotube (CNT) composites and their impact on multifarious applications
  179. Interfacial interactions and reinforcing mechanisms of cellulose and chitin nanomaterials and starch derivatives for cement and concrete strength and durability enhancement: A review
  180. Diamond-like carbon films for tribological modification of rubber
  181. Layered double hydroxides (LDHs) modified cement-based materials: A systematic review
  182. Recent research progress and advanced applications of silica/polymer nanocomposites
  183. Modeling of supramolecular biopolymers: Leading the in silico revolution of tissue engineering and nanomedicine
  184. Recent advances in perovskites-based optoelectronics
  185. Biogenic synthesis of palladium nanoparticles: New production methods and applications
  186. A comprehensive review of nanofluids with fractional derivatives: Modeling and application
  187. Electrospinning of marine polysaccharides: Processing and chemical aspects, challenges, and future prospects
  188. Electrohydrodynamic printing for demanding devices: A review of processing and applications
  189. Rapid Communications
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https://doi.org/10.1515/ntrev-2022-0085
Keywords for this article
photocatalysts; nitrogen doping; TiO2 nanotubes; graphitic carbon nitride; nanocomposites
Creative Commons
BY 4.0

Articles in the same Issue

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  3. Mechanical, morphological, and fracture-deformation behavior of MWCNTs-reinforced (Al–Cu–Mg–T351) alloy cast nanocomposites fabricated by optimized mechanical milling and powder metallurgy techniques
  4. Flammability and physical stability of sugar palm crystalline nanocellulose reinforced thermoplastic sugar palm starch/poly(lactic acid) blend bionanocomposites
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  14. Octreotide-conjugated silver nanoparticles for active targeting of somatostatin receptors and their application in a nebulized rat model
  15. Controllable morphology of Bi2S3 nanostructures formed via hydrothermal vulcanization of Bi2O3 thin-film layer and their photoelectrocatalytic performances
  16. Development of (−)-epigallocatechin-3-gallate-loaded folate receptor-targeted nanoparticles for prostate cancer treatment
  17. Enhancement of the mechanical properties of HDPE mineral nanocomposites by filler particles modulation of the matrix plastic/elastic behavior
  18. Effect of plasticizers on the properties of sugar palm nanocellulose/cinnamon essential oil reinforced starch bionanocomposite films
  19. Optimization of nano coating to reduce the thermal deformation of ball screws
  20. Preparation of efficient piezoelectric PVDF–HFP/Ni composite films by high electric field poling
  21. MHD dissipative Casson nanofluid liquid film flow due to an unsteady stretching sheet with radiation influence and slip velocity phenomenon
  22. Effects of nano-SiO2 modification on rubberised mortar and concrete with recycled coarse aggregates
  23. Mechanical and microscopic properties of fiber-reinforced coal gangue-based geopolymer concrete
  24. Effect of morphology and size on the thermodynamic stability of cerium oxide nanoparticles: Experiment and molecular dynamics calculation
  25. Mechanical performance of a CFRP composite reinforced via gelatin-CNTs: A study on fiber interfacial enhancement and matrix enhancement
  26. A practical review over surface modification, nanopatterns, emerging materials, drug delivery systems, and their biophysiochemical properties for dental implants: Recent progresses and advances
  27. HTR: An ultra-high speed algorithm for cage recognition of clathrate hydrates
  28. Effects of microalloying elements added by in situ synthesis on the microstructure of WCu composites
  29. A highly sensitive nanobiosensor based on aptamer-conjugated graphene-decorated rhodium nanoparticles for detection of HER2-positive circulating tumor cells
  30. Progressive collapse performance of shear strengthened RC frames by nano CFRP
  31. Core–shell heterostructured composites of carbon nanotubes and imine-linked hyperbranched polymers as metal-free Li-ion anodes
  32. A Galerkin strategy for tri-hybridized mixture in ethylene glycol comprising variable diffusion and thermal conductivity using non-Fourier’s theory
  33. Simple models for tensile modulus of shape memory polymer nanocomposites at ambient temperature
  34. Preparation and morphological studies of tin sulfide nanoparticles and use as efficient photocatalysts for the degradation of rhodamine B and phenol
  35. Polyethyleneimine-impregnated activated carbon nanofiber composited graphene-derived rice husk char for efficient post-combustion CO2 capture
  36. Electrospun nanofibers of Co3O4 nanocrystals encapsulated in cyclized-polyacrylonitrile for lithium storage
  37. Pitting corrosion induced on high-strength high carbon steel wire in high alkaline deaerated chloride electrolyte
  38. Formulation of polymeric nanoparticles loaded sorafenib; evaluation of cytotoxicity, molecular evaluation, and gene expression studies in lung and breast cancer cell lines
  39. Engineered nanocomposites in asphalt binders
  40. Influence of loading voltage, domain ratio, and additional load on the actuation of dielectric elastomer
  41. Thermally induced hex-graphene transitions in 2D carbon crystals
  42. The surface modification effect on the interfacial properties of glass fiber-reinforced epoxy: A molecular dynamics study
  43. Molecular dynamics study of deformation mechanism of interfacial microzone of Cu/Al2Cu/Al composites under tension
  44. Nanocolloid simulators of luminescent solar concentrator photovoltaic windows
  45. Compressive strength and anti-chloride ion penetration assessment of geopolymer mortar merging PVA fiber and nano-SiO2 using RBF–BP composite neural network
  46. Effect of 3-mercapto-1-propane sulfonate sulfonic acid and polyvinylpyrrolidone on the growth of cobalt pillar by electrodeposition
  47. Dynamics of convective slippery constraints on hybrid radiative Sutterby nanofluid flow by Galerkin finite element simulation
  48. Preparation of vanadium by the magnesiothermic self-propagating reduction and process control
  49. Microstructure-dependent photoelectrocatalytic activity of heterogeneous ZnO–ZnS nanosheets
  50. Cytotoxic and pro-inflammatory effects of molybdenum and tungsten disulphide on human bronchial cells
  51. Improving recycled aggregate concrete by compression casting and nano-silica
  52. Chemically reactive Maxwell nanoliquid flow by a stretching surface in the frames of Newtonian heating, nonlinear convection and radiative flux: Nanopolymer flow processing simulation
  53. Nonlinear dynamic and crack behaviors of carbon nanotubes-reinforced composites with various geometries
  54. Biosynthesis of copper oxide nanoparticles and its therapeutic efficacy against colon cancer
  55. Synthesis and characterization of smart stimuli-responsive herbal drug-encapsulated nanoniosome particles for efficient treatment of breast cancer
  56. Homotopic simulation for heat transport phenomenon of the Burgers nanofluids flow over a stretching cylinder with thermal convective and zero mass flux conditions
  57. Incorporation of copper and strontium ions in TiO2 nanotubes via dopamine to enhance hemocompatibility and cytocompatibility
  58. Mechanical, thermal, and barrier properties of starch films incorporated with chitosan nanoparticles
  59. Mechanical properties and microstructure of nano-strengthened recycled aggregate concrete
  60. Glucose-responsive nanogels efficiently maintain the stability and activity of therapeutic enzymes
  61. Tunning matrix rheology and mechanical performance of ultra-high performance concrete using cellulose nanofibers
  62. Flexible MXene/copper/cellulose nanofiber heat spreader films with enhanced thermal conductivity
  63. Promoted charge separation and specific surface area via interlacing of N-doped titanium dioxide nanotubes on carbon nitride nanosheets for photocatalytic degradation of Rhodamine B
  64. Elucidating the role of silicon dioxide and titanium dioxide nanoparticles in mitigating the disease of the eggplant caused by Phomopsis vexans, Ralstonia solanacearum, and root-knot nematode Meloidogyne incognita
  65. An implication of magnetic dipole in Carreau Yasuda liquid influenced by engine oil using ternary hybrid nanomaterial
  66. Robust synthesis of a composite phase of copper vanadium oxide with enhanced performance for durable aqueous Zn-ion batteries
  67. Tunning self-assembled phases of bovine serum albumin via hydrothermal process to synthesize novel functional hydrogel for skin protection against UVB
  68. A comparative experimental study on damping properties of epoxy nanocomposite beams reinforced with carbon nanotubes and graphene nanoplatelets
  69. Lightweight and hydrophobic Ni/GO/PVA composite aerogels for ultrahigh performance electromagnetic interference shielding
  70. Research on the auxetic behavior and mechanical properties of periodically rotating graphene nanostructures
  71. Repairing performances of novel cement mortar modified with graphene oxide and polyacrylate polymer
  72. Closed-loop recycling and fabrication of hydrophilic CNT films with high performance
  73. Design of thin-film configuration of SnO2–Ag2O composites for NO2 gas-sensing applications
  74. Study on stress distribution of SiC/Al composites based on microstructure models with microns and nanoparticles
  75. PVDF green nanofibers as potential carriers for improving self-healing and mechanical properties of carbon fiber/epoxy prepregs
  76. Osteogenesis capability of three-dimensionally printed poly(lactic acid)-halloysite nanotube scaffolds containing strontium ranelate
  77. Silver nanoparticles induce mitochondria-dependent apoptosis and late non-canonical autophagy in HT-29 colon cancer cells
  78. Preparation and bonding mechanisms of polymer/metal hybrid composite by nano molding technology
  79. Damage self-sensing and strain monitoring of glass-reinforced epoxy composite impregnated with graphene nanoplatelet and multiwalled carbon nanotubes
  80. Thermal analysis characterisation of solar-powered ship using Oldroyd hybrid nanofluids in parabolic trough solar collector: An optimal thermal application
  81. Pyrene-functionalized halloysite nanotubes for simultaneously detecting and separating Hg(ii) in aqueous media: A comprehensive comparison on interparticle and intraparticle excimers
  82. Fabrication of self-assembly CNT flexible film and its piezoresistive sensing behaviors
  83. Thermal valuation and entropy inspection of second-grade nanoscale fluid flow over a stretching surface by applying Koo–Kleinstreuer–Li relation
  84. Mechanical properties and microstructure of nano-SiO2 and basalt-fiber-reinforced recycled aggregate concrete
  85. Characterization and tribology performance of polyaniline-coated nanodiamond lubricant additives
  86. Combined impact of Marangoni convection and thermophoretic particle deposition on chemically reactive transport of nanofluid flow over a stretching surface
  87. Spark plasma extrusion of binder free hydroxyapatite powder
  88. An investigation on thermo-mechanical performance of graphene-oxide-reinforced shape memory polymer
  89. Effect of nanoadditives on the novel leather fiber/recycled poly(ethylene-vinyl-acetate) polymer composites for multifunctional applications: Fabrication, characterizations, and multiobjective optimization using central composite design
  90. Design selection for a hemispherical dimple core sandwich panel using hybrid multi-criteria decision-making methods
  91. Improving tensile strength and impact toughness of plasticized poly(lactic acid) biocomposites by incorporating nanofibrillated cellulose
  92. Green synthesis of spinel copper ferrite (CuFe2O4) nanoparticles and their toxicity
  93. The effect of TaC and NbC hybrid and mono-nanoparticles on AA2024 nanocomposites: Microstructure, strengthening, and artificial aging
  94. Excited-state geometry relaxation of pyrene-modified cellulose nanocrystals under UV-light excitation for detecting Fe3+
  95. Effect of CNTs and MEA on the creep of face-slab concrete at an early age
  96. Effect of deformation conditions on compression phase transformation of AZ31
  97. Application of MXene as a new generation of highly conductive coating materials for electromembrane-surrounded solid-phase microextraction
  98. A comparative study of the elasto-plastic properties for ceramic nanocomposites filled by graphene or graphene oxide nanoplates
  99. Encapsulation strategies for improving the biological behavior of CdS@ZIF-8 nanocomposites
  100. Biosynthesis of ZnO NPs from pumpkin seeds’ extract and elucidation of its anticancer potential against breast cancer
  101. Preliminary trials of the gold nanoparticles conjugated chrysin: An assessment of anti-oxidant, anti-microbial, and in vitro cytotoxic activities of a nanoformulated flavonoid
  102. Effect of micron-scale pores increased by nano-SiO2 sol modification on the strength of cement mortar
  103. Fractional simulations for thermal flow of hybrid nanofluid with aluminum oxide and titanium oxide nanoparticles with water and blood base fluids
  104. The effect of graphene nano-powder on the viscosity of water: An experimental study and artificial neural network modeling
  105. Development of a novel heat- and shear-resistant nano-silica gelling agent
  106. Characterization, biocompatibility and in vivo of nominal MnO2-containing wollastonite glass-ceramic
  107. Entropy production simulation of second-grade magnetic nanomaterials flowing across an expanding surface with viscidness dissipative flux
  108. Enhancement in structural, morphological, and optical properties of copper oxide for optoelectronic device applications
  109. Aptamer-functionalized chitosan-coated gold nanoparticle complex as a suitable targeted drug carrier for improved breast cancer treatment
  110. Performance and overall evaluation of nano-alumina-modified asphalt mixture
  111. Analysis of pure nanofluid (GO/engine oil) and hybrid nanofluid (GO–Fe3O4/engine oil): Novel thermal and magnetic features
  112. Synthesis of Ag@AgCl modified anatase/rutile/brookite mixed phase TiO2 and their photocatalytic property
  113. Mechanisms and influential variables on the abrasion resistance hydraulic concrete
  114. Synergistic reinforcement mechanism of basalt fiber/cellulose nanocrystals/polypropylene composites
  115. Achieving excellent oxidation resistance and mechanical properties of TiB2–B4C/carbon aerogel composites by quick-gelation and mechanical mixing
  116. Microwave-assisted sol–gel template-free synthesis and characterization of silica nanoparticles obtained from South African coal fly ash
  117. Pulsed laser-assisted synthesis of nano nickel(ii) oxide-anchored graphitic carbon nitride: Characterizations and their potential antibacterial/anti-biofilm applications
  118. Effects of nano-ZrSi2 on thermal stability of phenolic resin and thermal reusability of quartz–phenolic composites
  119. Benzaldehyde derivatives on tin electroplating as corrosion resistance for fabricating copper circuit
  120. Mechanical and heat transfer properties of 4D-printed shape memory graphene oxide/epoxy acrylate composites
  121. Coupling the vanadium-induced amorphous/crystalline NiFe2O4 with phosphide heterojunction toward active oxygen evolution reaction catalysts
  122. Graphene-oxide-reinforced cement composites mechanical and microstructural characteristics at elevated temperatures
  123. Gray correlation analysis of factors influencing compressive strength and durability of nano-SiO2 and PVA fiber reinforced geopolymer mortar
  124. Preparation of layered gradient Cu–Cr–Ti alloy with excellent mechanical properties, thermal stability, and electrical conductivity
  125. Recovery of Cr from chrome-containing leather wastes to develop aluminum-based composite material along with Al2O3 ceramic particles: An ingenious approach
  126. Mechanisms of the improved stiffness of flexible polymers under impact loading
  127. Anticancer potential of gold nanoparticles (AuNPs) using a battery of in vitro tests
  128. Review Articles
  129. Proposed approaches for coronaviruses elimination from wastewater: Membrane techniques and nanotechnology solutions
  130. Application of Pickering emulsion in oil drilling and production
  131. The contribution of microfluidics to the fight against tuberculosis
  132. Graphene-based biosensors for disease theranostics: Development, applications, and recent advancements
  133. Synthesis and encapsulation of iron oxide nanorods for application in magnetic hyperthermia and photothermal therapy
  134. Contemporary nano-architectured drugs and leads for ανβ3 integrin-based chemotherapy: Rationale and retrospect
  135. State-of-the-art review of fabrication, application, and mechanical properties of functionally graded porous nanocomposite materials
  136. Insights on magnetic spinel ferrites for targeted drug delivery and hyperthermia applications
  137. A review on heterogeneous oxidation of acetaminophen based on micro and nanoparticles catalyzed by different activators
  138. Early diagnosis of lung cancer using magnetic nanoparticles-integrated systems
  139. Advances in ZnO: Manipulation of defects for enhancing their technological potentials
  140. Efficacious nanomedicine track toward combating COVID-19
  141. A review of the design, processes, and properties of Mg-based composites
  142. Green synthesis of nanoparticles for varied applications: Green renewable resources and energy-efficient synthetic routes
  143. Two-dimensional nanomaterial-based polymer composites: Fundamentals and applications
  144. Recent progress and challenges in plasmonic nanomaterials
  145. Apoptotic cell-derived micro/nanosized extracellular vesicles in tissue regeneration
  146. Electronic noses based on metal oxide nanowires: A review
  147. Framework materials for supercapacitors
  148. An overview on the reproductive toxicity of graphene derivatives: Highlighting the importance
  149. Antibacterial nanomaterials: Upcoming hope to overcome antibiotic resistance crisis
  150. Research progress of carbon materials in the field of three-dimensional printing polymer nanocomposites
  151. A review of atomic layer deposition modelling and simulation methodologies: Density functional theory and molecular dynamics
  152. Recent advances in the preparation of PVDF-based piezoelectric materials
  153. Recent developments in tensile properties of friction welding of carbon fiber-reinforced composite: A review
  154. Comprehensive review of the properties of fly ash-based geopolymer with additive of nano-SiO2
  155. Perspectives in biopolymer/graphene-based composite application: Advances, challenges, and recommendations
  156. Graphene-based nanocomposite using new modeling molecular dynamic simulations for proposed neutralizing mechanism and real-time sensing of COVID-19
  157. Nanotechnology application on bamboo materials: A review
  158. Recent developments and future perspectives of biorenewable nanocomposites for advanced applications
  159. Nanostructured lipid carrier system: A compendium of their formulation development approaches, optimization strategies by quality by design, and recent applications in drug delivery
  160. 3D printing customized design of human bone tissue implant and its application
  161. Design, preparation, and functionalization of nanobiomaterials for enhanced efficacy in current and future biomedical applications
  162. A brief review of nanoparticles-doped PEDOT:PSS nanocomposite for OLED and OPV
  163. Nanotechnology interventions as a putative tool for the treatment of dental afflictions
  164. Recent advancements in metal–organic frameworks integrating quantum dots (QDs@MOF) and their potential applications
  165. A focused review of short electrospun nanofiber preparation techniques for composite reinforcement
  166. Microstructural characteristics and nano-modification of interfacial transition zone in concrete: A review
  167. Latest developments in the upconversion nanotechnology for the rapid detection of food safety: A review
  168. Strategic applications of nano-fertilizers for sustainable agriculture: Benefits and bottlenecks
  169. Molecular dynamics application of cocrystal energetic materials: A review
  170. Synthesis and application of nanometer hydroxyapatite in biomedicine
  171. Cutting-edge development in waste-recycled nanomaterials for energy storage and conversion applications
  172. Biological applications of ternary quantum dots: A review
  173. Nanotherapeutics for hydrogen sulfide-involved treatment: An emerging approach for cancer therapy
  174. Application of antibacterial nanoparticles in orthodontic materials
  175. Effect of natural-based biological hydrogels combined with growth factors on skin wound healing
  176. Nanozymes – A route to overcome microbial resistance: A viewpoint
  177. Recent developments and applications of smart nanoparticles in biomedicine
  178. Contemporary review on carbon nanotube (CNT) composites and their impact on multifarious applications
  179. Interfacial interactions and reinforcing mechanisms of cellulose and chitin nanomaterials and starch derivatives for cement and concrete strength and durability enhancement: A review
  180. Diamond-like carbon films for tribological modification of rubber
  181. Layered double hydroxides (LDHs) modified cement-based materials: A systematic review
  182. Recent research progress and advanced applications of silica/polymer nanocomposites
  183. Modeling of supramolecular biopolymers: Leading the in silico revolution of tissue engineering and nanomedicine
  184. Recent advances in perovskites-based optoelectronics
  185. Biogenic synthesis of palladium nanoparticles: New production methods and applications
  186. A comprehensive review of nanofluids with fractional derivatives: Modeling and application
  187. Electrospinning of marine polysaccharides: Processing and chemical aspects, challenges, and future prospects
  188. Electrohydrodynamic printing for demanding devices: A review of processing and applications
  189. Rapid Communications
  190. Structural material with designed thermal twist for a simple actuation
  191. Recent advances in photothermal materials for solar-driven crude oil adsorption
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