Volume 6, Issue 2

CuInS 2 /ZnS (CIS/ZnS) quantum dots (QDs) with high photoluminescence (PL) were synthesized via a facile solvothermal approach. Gaussian deconvolution of PL spectra, transmission electron microscopy, and time-resolved PL spectroscopies were used to characterize the emission properties of the prepared CIS and CIS/ZnS QDs. It was found that the growth of ZnS can reduce the surface defect acting as traps to minimize donor-acceptor emissions, and the contribution of band to donor/acceptor transition becomes a dominating emission with the increase of shell growth time. The blue shift of PL emission wavelength of CIS/ZnS QDs underwent two steps: the dramatic blue shift originated from the decreased fraction donor-acceptor transition due to the reduction of surface defects at the beginning and the subsequently mild blue-shift with the time from the interdiffusion of CIS and ZnS. The effect of trioctylphosphine (TOP) and dodecanethiol (DDT) as ligands during shell growth on the optical properties of QDs were investigated and compared. The PL quantum yield (QY) of CIS core affects the final value of CIS/ZnS QDs, and the higher PL QY is achieved while using CIS core with higher PL QY. Based on the selected ligand DDT, the reaction parameters, such as CIS core reaction time, shell growth time, and Zn/Cu feed molar ratio, were further optimized. CIS/ZnS QDs with high PL QY can be obtained with a Zn/Cu feed molar ratio larger than 4, shell growth time of 30 to 90 min, and shell growth temperature 220°C–240°C, and the maximum value was up to about 80% by adjusting the above-mentioned parameters.

The aim of this work was to acquire even and sphere-shaped silver nanoparticles (AgNPs) using statistical design of experiment. AgNPs were produced by green synthesis method using deoiled Saccharina japonica powder obtained after supercritical carbon dioxide (Sc-CO 2 ) extraction. Based on the Box-Behnken design, three variables influencing the size of AgNPs produced were identified as silver nitrate (AgNO 3 ) concentration, temperature, and reaction time. Optimum conditions were determined using response surface methodology for synthesis of AgNPs. We found that increasing reaction time at low concentration of AgNO 3 resulted in smaller particle size, and conversely increasing reaction time at high concentration of AgNO 3 resulted in bigger particles. The obtained AgNPs were characterized by transmission electron microscopy, energy dispersive X-ray, X-ray diffraction analysis, and ultraviolet-visible and Fourier transform infrared spectroscopy techniques for particle size, distribution, aggregation, and anisotropy. The optimum operating conditions are 1 m m of AgNO 3 , 40°C, and 45 min with the smallest AgNPs size being 14.77 nm. The optimized AgNPs showed good antimicrobial activity and excellent sensing behavior towards hydrogen peroxide. The polyphenols present in aqueous AgNPs were evaluated by high-pressure liquid chromatography, which revealed the existence of chlorogenic acid and rutin.

The preparation of Mo x S y nanoparticles with different morphologies via a surfactant-assisted one-pot solvothermal route was reported. The concentration of surfactant was studied to evaluate its effects on the morphology and the size of the as obtained nanoparticles. The final products were comprehensively characterized using XRD, TEM, HRTEM, IR, TGA and XPS. It was found that at low surfactant concentration, MoS 2 spherical shapes were obtained whereas tubular morphologies are formed at higher concentration. This issue has been discussed based on various relevant experimental data.

The green synthetic route for the synthesis of semiconductor nanoparticles has received special attention recently due to its features, such as low cost and environmental friendliness. The (Z)-2-(pyrrolidin-2-ylidene)thiourea was used as a ligand and allowed to react with zinc acetate to form the ZnS nanoparticles through the homogeneous precipitation method. The polyvinyl pyrrolidone and polyethylene glycol were employed as capping agents, whereas the ammonium solution was used as an activator for the stabilizers. The effects of the concentration of the capping agents on ZnS nanoparticles were investigated. The poly ethylene glycol (PEG)- or (polyvinylpyrollidone) PVP-capped zinc sulfide nanoparticles were then incorporated with polydadmac to form the polymer nanocomposites. The results from various sophisticated instruments, such as spectrophotometer (UV-Vis), photoluminescence (PL), Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscope (TEM), and scanning electron microscopy (SEM), reveal that the concentrations of capping agents and ammonium solution has great effects on nanomaterials.

Employing a capping agent during the synthesis of nanoparticles has been reported to play a role in controlling size and shape of the nanoparticles. Due to this reason, this study reports the synthesis of silver selenide nanoparticles using different environmentally friendly capping agents (green tea, glucose, ascorbic acid and chitosan) in order to investigate their effect on the size and shape of the nanoparticles. Transmission electron microscopy (TEM) results showed that the nanoparticles have different shapes (rods, spheres and cubes) with an average size of 8–96 nm depending on the capping agent used. Fourier transformer infrared (FTIR) spectroscopy confirmed that the capping of nanoparticles was successful, while X-ray diffraction (XRD) showed that the nanoparticles have an orthorhombic phase.

The present paper reports the experimental details for the synthesis of performic acid (PFA) using Corning advanced-flow reactors (AFRs) using formic acid and H 2 O 2 as reactants, and sulfuric acid as homogeneous catalyst. The effect of different operating parameters on PFA concentration such as reactant flow rates (residence time), temperature, reactant and catalyst concentration were studied. The experimental results indicate that the heart-shaped pellet structure in AFR provides better mixing, and hence more conversion with less residence time achieved. Moreover, AFR technology offers the possibility to conduct chemical reactions in a more sustainable way due to miniaturization and increased safety. Reactions show optimum results at 30°C with a feed flow rate of 80 ml/h in the presence of 1 w/w % H 2 SO 4 as catalyst. The optimized results demonstrated the capability of AFR technology for enhancement in the formation of PFA (time equal to 1 min) with high conversion (95.85%). Further, it has been found that the concentration of PFA was reached at maximum value within 1 min of time. Therefore, the production of PFA is very fast in a microreactor, which saves our time and energy and in turn it saves the environment on fuel requirement and therefore this process is green.

Recent synthetic methods for α-hydroxyphosphonates comprise a green, solvent-free accomplishment of the Pudovik reaction that was typically followed by extractions and recrystallization, or even by chromatography, or other operations. We now developed a general procedure applying 10% of triethylamine as the catalyst and a minimum quantity of acetone as the solvent, giving the products in a pure form after a reflux of 5–120 min following the addition of some n -pentane and crystallization on cooling.

N- allylanilines are important compounds that are used to access several bioactive compounds containing indole and dihydroindole nucleus. However, their preparation through allylation can lead to the undesirable N , N -diallyl byproduct. In this work, the N -allylation of 4-chloroaniline was studied. In order to accelerate the process and maximize the monoallylated:diallylated ratio, we reported two full factorial studies to transpose the conventional synthetic procedure to an ultrasound (US) methodology. The evaluated factors were temperature, quantity of reagents (allyl bromide and K 2 CO 3 ), reaction time, and methodology (conventional or US). The results showed that US did not change the monoallylated:diallylated ratio, but significantly improved the reaction rate, giving increased average monoallylated and total yields of 11.4% and 18.1%, respectively (p<0.05). The proposed US methodology gave the same yields and product ratio in a 4-h reaction time than the conventional 24-h procedure, without heating and using only an inexpensive US bath to conduct the reactions.

Vast jarosite residue was produced from traditional zinc hydrometallurgy process in China. It is necessary to recover valuable metals from the jarosite residue. Indium is the one of them. Recovering indium from jarosite residues with carbon reduction method under the condition of vacuum was investigated. The analysis of variance was used to evaluate the influence of different factors on the volatilizing rate of indium, indicating that the influence of temperature on the volatilizing rate of indium is statistically significant. Other factors have no significant influence. Response surface methodology was used to explore the best combination of four variables and to study the effects of their interactions on the indium volatilizing rate. The results showed that there was an obvious interaction between the percent content of carbon and temperature and between the percent content of carbon and hold time, and the selected optimal conditions were 30% carbon, 13% CaO, 1000°C temperature, and 60 min hold time. Under these conditions, the indium volatilization rate was up to 98.2%.

Recovery of rare earth from the waste rare earth polishing powder is of great importance to improve the process economics. The current recovery methods result in the generation of large quantities of polluted discharge necessitating waste treatment systems. The present work attempts to extract cerium from rare earth slurry waste by thiourea reducing and hydrochloric acid leaching, towards which central composite technique of the response surface methodology is adopted to design the experiments and to optimize the process conditions to maximize the recovery rate. The effects of four major parameters such as temperature, duration of leaching, dosage of thiourea, and the concentration of HCl were assessed, and the optimal process conditions were identified. Analysis of variance (ANOVA) was utilized to identify the suitable model and to eliminate the insignificant model parameters. The optimized process conditions for maximizing the recovery rate are identified to be a leaching temperature of 90°C, duration of 150 min, thiourea dosage of 0.2 g/g, and HCl concentration of 3.5 mol/l. A recovery of 91.23% could be achieved and validated through repeat experimental runs at the optimized process conditions. The optimized process samples are characterized utilizing XRD to validate the recovery.

The utilization of inert recycled materials obtained from construction and demolition waste must be assessed, among others, in terms of their potential impacts on the environment and human health. The ecological suitability for subsequent applications is proven based on their chemical composition, the content of harmful substances, and their potential leakage into the surrounding environment. The ecological criteria are always determined according to the requirements of the legislation in force and according to the demand for a specific type of waste and its utilization. However, the specification of limit values for the evaluation of the content of harmful substances and other monitored parameters is a questionable issue. This article presents the results of an experimental program focused on the monitoring of the environmental risks of recycled aggregates. The analysis of the results of laboratory tests of recycled bricks, recycled concrete, and soil with aggregates points out the difficulty in complying with the conditions for the potential utilization of these recycled materials on ground surfaces. The objective of these tests is to compare the results of laboratory tests of recycled bricks, recycled concrete, and soil with aggregates obtained from different recycling facilities to the limit values stipulated by legislative regulations.

The present work briefs the extraction of different kinds of nutraceutical plant molecules from different plants for the first time by using the remarkable extraction ability of a safe, “green” solvent: alkaline sucrose. The developed process was initially applied to isolate β,β-dimethylacryl shikonin (BDMS) and ursolic acid (UA) from Arnebia nobilis and Cotoneaster buxifolia , respectively. The extractive efficiency was determined by HPLC-DAD analysis. The versatility of the alkaline sucrose as extractive solvent was later confirmed by isolating four more different molecules from their respective plant matrices with significant recovery and purity. Further optimization by Box-Behnken experimental design model yielded a maximized amount of BDMS (18.2 mg/g of DM) and UA (2.2 mg/g of DM) with a high correlation coefficient (0.98–0.99), demonstrating a good fit between the regression model (second order) and the experimental results. The final purity of compounds through optimized process was greater than 90% (e.g. BDMS: 93%, UA: 96%, etc.). The optimized yields signify remarkable increase in final yield of compounds (e.g. BDMS: 152%, UA: 200%, etc.) than conventional solvent-based plant compound extraction, thus making the developed process a benign, green route for rapid isolation of plant compounds.

Green, sensitive and selective spectrophotometric methods were developed for the determination of nitrite in water samples. The methods (A, B and C) are based on the reduction of 5-nitroimidazoles; metronidazole (MTL), secnidazole (SCL) and tinidazole (TNL), respectively, followed by diazotization using nitrite in acidic medium, then coupling with pyrogallol (PG). The amount of nitrite was determined by measuring the absorbance of the colored product at 385 nm. The new methods were linear in the ranges of 2.5–30 μgml −1 , with detection limits of 1.4 μgml −1 .