Volume 4, Issue 5 - Special issue: Frontiers in nanoscience, technology and applications/Issue editors: Apparao M. Rao and Deepika Saini

Shrinking transistor sizes and power dissipation are the major barriers in the development of future computational circuits. At least when the transistor size approaches the atomic scale, duplication of transistor density according to Moore’s law will not be possible. Physical limits, like quantum effects and nondeterministic behavior of small currents, and technological limits, such as high power consumption and design complexity, may hold back the future program of microelectronic conventional circuit scaling. Hence, an alternative technology is required for future design. Quantum dot-cellular automata (QCA) is a transistor-less, very promising nanotechnology that can be used to build nanocircuits. The conventional computer is an irreversible one; i.e. once a logic block generates the output bits, the input bits are lost. A possible solution is reversible computing, where no bit is lost during computation. Hence, logically reversible circuit can consume less energy than any conventional circuit. In this paper, a brief review on evolution of the QCA in reversible computing is discussed. Various reversible gates that are designed using QCA technology as well as the modification of those designs that are made in latter works are highlighted.

Thiolated amino acids are biologically important molecules due to their role in protein folding and structure. One such molecule is cysteine (Cys), which acts as a biomarker for diseases like cancer, HIV, sepsis, etc., making its rapid detection imperative and essential. In this study, we report the sensitive detection of the thiolated amino acid Cys, from the non-thiolated amino acid arginine (Arg), using the novel surface plasmon coupled emission (SPCE) platform, characterized with high signal-to-noise ratios. Our studies were performed on the conventional silver (Ag) SPCE substrate, where Cys was detected to a nanomolar level, which is a major improvement to the previously reported level of sensitivity. This can be attributed to the highly sensitive SPCE platform and the unique thiol-Ag interactions associated specifically with Cys. We have also shown the role and influence of the coating process on sensitivity of detection and substantiated the advantages of SPCE over the SPR-based strategy of detection. The simplistic and economical SPCE platform enabled the sensitive detection of Cys that is of biological and medical relevance.

Copper oxide (CuO) is one of the most important transition metal oxides due to its unique properties. It is used in various technological applications such as high critical temperature, superconductors, gas sensors, in photoconductive applications and so on. Recently, it has been used as an antimicrobial agent against various pathogenic bacteria. In the present investigation, we studied the structural and antidermatophytic properties of CuO nanoparticles (NPs) synthesized by a precipitation technique. Copper sulfate was used as a precursor and sodium hydroxide as a reducing agent. Scanning electron microscopy (SEM) showed flower-shaped CuO NPs and X-ray diffraction (XRD) pattern showed the crystalline nature of CuO NPs. These NPs were evaluated against two prevalent species of dermatophytes, i.e. Trichophyton rubrum and T. mentagrophytes by using the broth microdilution technique. Further, the NPs activity was also compared with synthetic sertaconazole. Although better antidermatophytic activity was exhibited with sertaconazole as compared to NPs, being synthetic, sertaconazole may not be preferred, as it shows different adverse effects. Trichophyton mentagrophytes is more susceptible to NPs than T. rubrum . A phylogenetic approach was applied for predicting differences in susceptibility of pathogens.

Here, we present a new ball-milling and spark plasma sintering (SPS)-based technique for the facile synthesis of FeSe 0.5 Te 0.5 superconductors without the need for pre-alloying. This method is advantageous since it is quick and flexible for incorporating other dopants such as graphene for vortex pinning. We observed that FeSe 0.5 Te 0.5 exhibits a coexistence of ferromagnetic (FM) and superconductivity signature plausibly arising from a FM core-superconducting shell structure. More importantly, the H c 2 values observed from resistivity data are higher than 7 T, indicating that SPS process synthesized FeSe 0.5 Te 0.5 samples could lead to next-generation superconducting wires and cables.

Organic bulk heterojunction solar cells are a promising candidate for low-cost next-generation photovoltaic systems. In bulk heterojunction polymer solar cells, conjugated polymers and fullerene derivatives [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) function as the electron-donating and electron-accepting materials, respectively. In this paper, we report the photovoltaic response of the solution-processed bulk heterojunction (BHJ) solar cell based on poly (2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV): modified PCBM (MPCBM) blend. The BHJ showed power conversion efficiency (PCE) up to 1.78%. The PCE has been further improved up to 1.95% after thermal annealing of the active layer. The increase in the PCE with the thermally annealed blend is mainly attributed to the improvement in incident photon to current efficiency (IPCE) and short circuit photocurrent (J sc ).

Conducting polymer-wide band gap semiconductor nanocomposites are prepared by polymerizing pyrrole in the presence of colloidal titanium dioxide (TiO 2 ) sol. Characterizations of nanocomposites are carried out by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Direct current (dc) and alternating current (ac) conductivities of nanocomposites have been investigated as a function of temperature and frequency for different concentrations of polypyrrole (PPY). The temperature dependence of ac conductivity suggests that small polaron tunneling occurs in the charge transfer process. A very large dielectric constant of about 13,000 at room temperature has been observed. The interface between PPY and TiO 2 plays an important role in yielding a large dielectric constant in the composite.

Several soil microbes are present in the rhizosphere zone, especially plant growth promoting rhizobacteria (PGPR), which are best known for their plant growth promoting activities. The present study reflects the effect of gold nanoparticles (GNPs) at various concentrations on the growth of PGPR. GNPs were synthesized chemically, by reduction of HAuCl4, and further characterized by UV-Vis spectroscopy, X-ray diffraction technique (XRD), and transmission electron microscopy (TEM), etc. The impact of GNPs on PGPR was investigated by Clinical Laboratory Standards Institute (CLSI) recommended Broth-Microdilution technique against four selected PGPR viz ., Pseudomonas fluorescens , Bacillus subtilis , Paenibacillus elgii , and Pseudomonas putida . Neither accelerating nor reducing impact was observed in P. putida due to GNPs. On the contrary, significant increase was observed in the case of P. fluorescens , P. elgii , and B. subtilis , and hence, GNPs can be exploited as nano-biofertilizers.

The nanosized titanium oxide (TiO 2 ) nanoparticles (NPs) were synthesized via sol-gel method. The crystalline nature of the synthesized TiO 2 nanoparticles was confirmed by X-ray powder diffractometry method. The surface morphology and particle size of the nanoparticles were analyzed by high-resolution scanning electron microscopic method. UV-visible spectroscopy was employed to determine its band gap energy value. The different concentrations of nanofluid samples of TiO 2 NPs dispersed in ethylene glycol were prepared and mixed thoroughly by ultrasonication process. The value of ultrasonic velocity and density were measured for the different concentrations of TiO 2 nanofluids. The acoustical parameters such as adiabatic compressibility, intermolecular free length, and acoustic impedance were calculated from the experimental data. It was observed that ultrasonic velocity showed linearity with particle concentration, and the results were discussed. In addition to the TiO 2 -ethylene glycol (particle-fluid) interaction studies, a new methodology was proposed to find the thermal conductivity of nanofluids using ultrasonic velocity.

This paper presents a novel class of multiwalled carbon nanotubes (MWCNTs) and zinc oxide (ZnO) doped polyvinyl alcohol (PVA) nanocomposites prepared using coagulation and solvent casting method. The dopant, ZnO nanoparticles, was prepared using precipitation method, and another dopant, MWCNTs, was treated with H 2 SO 4 and HNO 3 taken in 3:1volume ratio to create carboxylated MWCNTs. Furthermore, prepared ZnO and treated MWCNTs were doped into PVA matrix to prepare PVA nanocomposites by solvent casting technique. The Fourier transform infrared (FTIR) spectra detect the irregular shift in the bands of doped PVA nanocomposites indicating the presence of intra/intermolecular hydrogen bonding creating the interaction between the nanoparticles and neighboring OH group of PVA. Crystallinity of the prepared nanocomposites films was investigated using XRD technique, which explores the average particle size of the embedded nanoparticles and explains the complex formation and variation in crystallinity of the nanocomposites due to interaction of dopants. The decrease in optical energy band gap of nanocomposite films and the information of Urbach energy (E u ) were assessed by UV/vis spectroscopy. By using a universal testing machine, the mechanical properties of doped polymer films found escalation for doping percentage concentration x =7.5 wt%. The phase homogeneity, film morphology, and chemical configuration of the nanocomposites were inspected using atomic force microscope, scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively.

Recently, iron disulphide (FeS 2 ) has been considered as a potential solar absorber material due to several factors. These include more abundance and less toxicity of the elements involved, suitable energy band gap (0.95 eV) with high optical absorption coefficient and sufficiently long minority carrier diffusion length to produce short circuit currents >30 mA. Thin films of FeS 2 have been grown by a variety of physical as well as chemical methods. In this work, a simple wet chemical process, chemical bath deposition, was used to synthesise FeS 2 films using iron sulphate and thiourea as precursors. Ammonia was used in combination with EDTA as a novel complexing agent to form the layers for the first time. The films were deposited using different bath temperatures (T b ) that vary in the range 50°C–70°C, keeping the other deposition parameters constant. The chemical and physical properties of the films were investigated using appropriate techniques.

The chalcopyrite semiconductors belonging to the I 2 -II-IV-VI 4 class are emerging as promising absorber materials for photovoltaic applications. Among them, Cu 2 ZnSnS 4 (CZTS) has been gaining importance due to its high absorption coefficient and optimum band-gap. To make CZTS an economically viable alternative, in this study, the CZTS powder has been synthesized via a low-cost, environment-friendly reflux method. In the current method, the salts of the respective metals were taken as initial precursors, and thiourea was used as a precursor for sulfur. The stoichiometric amounts of the precursors were taken in distilled water and the solution was refluxed for 8 h. The products were filtered and washed with distilled water and ethanol consecutively. Phase identification was done using powder X-ray diffraction (given by the reference pattern JCPDS card no. #00-026-0575) and Raman spectroscopy analysis (corresponding Raman shifts for CZTS: 288 and 338 cm -1 ). The band gap of the compound was calculated from the UV-visible spectroscopy and found to be 1.4 eV.

Our increasing energy demands have spurred a rigorous search for renewable energy sources to reduce our dependence on fossil fuels. However, efficient use of renewable energy is possible only with advances in both energy generation and storage. Today’s batteries and capacitors, which are the main energy storage devices, cannot meet the world’s demand for combined power and energy densities. To enhance the viability of such energy storing devices, the Clemson Nanomaterials Center (CNC) has developed a mix of scalable processes for carbon nanotube-based hybrid electrodes that show promise as a cost-effective alternative to standard activated carbon-based electrodes. Working together with industrial partners, CNC has fabricated supercapacitors with energy and power densities in the range of ~11–35 Wh/kg and ~1.2–9 W/kg, respectively. Although this research development is transformative, further studies to optimize the separator and electrolyte technologies are needed to maximize both the energy and power density in a single device.