Facile synthesis of CdS nanocrystals using thioglycolic acid as a sulfur source and stabilizer in aqueous solution

A novel method has been developed for the synthesis of CdS nanocrystals (NCs) using thioglycolic acid (TGA) as a sulfur source and stabilizer with the presence of hydrogen peroxide in an aqueous medium. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the product was of zinc-blend crystal structure in a sphere-like shape. The room-temperature luminescence spectra revealed that the emission peak of CdS NCs prepared in relatively short refluxing times (10-120 min) could be tuned from 518 nm to 610 nm, and the photoluminescence quantum yield of the as-prepared CdS NCs could reach as high as 12.6%. In addition, the mechanism of the CdS nanocrystals formation was preliminarily discussed.KEY WORDS: Chemical synthesis, CdS, Nanostructures, Optical properties, Photoluminescence spectroscopy Bull. Chem. Soc. Ethiop. 2011, 25(3), 393-398

Citric Acid Modified Bentonite for Congo Red Adsorption

Raw bentonite (RB) was chemically modified by citric acid (CA) to obtain a low-cost and environment-friendly citric acid incorporated bentonite (CAB) adsorbent, which was applied for the adsorptive removal of Congo Red (CR). The effect of adsorbent dosage, contact time, ionic strength, surfactant, and pH on adsorption was investigated. Adsorption equilibrium data fitted well with Langmuir model while the Langmuir adsorption capacity of CR on CAB reached up to 384 mg·g−1. Furthermore, CR adsorption on CAB followed pseudo-second kinetic model while intra-particle diffusion was not the only rate-limiting step as determined from intra-particle diffusion model investigation. RB and CAB were characterized by XRD, FT-IR, and BET techniques. A proposed mechanism for the adsorption of CR over CAB suggested the chemical adsorption phenomenon is mainly controlled by chelation, hydrogen bonding, and fixing

Optimum Design of a Solar-Wind-Diesel Hybrid Energy System with Multiple Types of Storage Devices Driving a Reverse Osmosis Desalination Process

To simultaneously satisfy the electricity and freshwater requirements, a superstructure of a solar-wind-diesel hybrid energy system (HES) with multiple types of storage devices driving a reverse osmosis desalination (ROD) process is established in this paper. The corresponding mathematical model of the HES, potentially including photovoltaic cells, a wind turbine, a diesel generator, a ROD unit, different battery storage technologies, or a water tank is developed and features mixed integer linear programming. The optimum design and operation schemes of the HES can be obtained by taking the minimum total annual cost as the optimization objective. To verify the effectiveness of the proposed method, an example of a solar-wind-diesel system for supplying a ROD process in Saudi Arabia is adopted. The results show that a photovoltaic panel, wind turbine, diesel generator, lead-acid battery, Li-ion battery and water tank are selected in the HES with the minimum total annual cost (i.e., 1.16 × 105 USD·y−1), by satisfying the requirement of the renewable energy penetration rate (i.e., 0.8). Then, a quantified method is proposed to determine the optimal design and operation schemes of the HES, including both economic and environmental aspects. Finally, the HES with various generators and multiple types of storage devices shows a better performance in terms of economy and renewable energy utilization

Facile synthesis of SrCO 3 nanostructures in methanol

Highly dispersive strontium carbonate (SrCO 3 ) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO 3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N 2 adsorption-desorption. The results showed that the reaction temperature and the methanol 3 particles. The dumbbell-like SrCO 3 exhibited a Broader-Emmett-Teller surface area of 14.9?m 2 ?g ?1 and an average pore size of about 32?nm with narrow pore size distribution. The formation mechanism of the SrCO 3 crystal was preliminary presented

Metal-Organic Framework Thin Films with Diverse Redox-Active/Inactive Components for Enhanced Electrochromic Performance

Electrochromism is attractive due to the increasing demand for intelligent devices such as smart windows and display apparatuses. Metal-organic frameworks (MOFs) are found to be promising electrochromic materials thanks to their tailorable structures and chemical compositions via combining various metal centers and organic ligands. However, the uncovered redox mechanism, the insulating and inactive redox nature for majority of MOFs have hampered their practical application as efficient electrochromic materials. Herein, four MOF thin films (Cu-TCA, Zn-TCA, HKUST-1 and Zn-MOF-74) constructing from redox-active/inactive metal centers and organic ligands were prepared, and their electrochromic performance in a Li-ion-conducting electrolyte was present. We demonstrate that redox-active metal centers and organic ligands in MOFs contribute to the reversible and sustainable optical modulation. A further investigation was carried out to dope redox-active metal center Co2+ into the Cu-TCA thin film, serving as the second metal center. Unambiguous evidence shows that Co2+ doping can enlarge the specific surface area and pore volume of Cu-TCA to facilitate the transport and intercalation/deintercalation of ions and electrons, resulting in the enhanced transmittance modulation (70% at 705 nm) and coloration efficiency (337 cm2·C−1). Our work provides an important approach and guidance in designing efficient MOFs for electrochromic application

Crystallization control of SrCO3 nanostructure in imidazolium-based temperature ionic liquids

Strontium carbonate nanostructures, with unique nanowhisker, nanospindle, nanosphere, sphere, spindle, and rodlike hierarchical structure, were synthesized in imidazolium-based room temperature ionic liquids [C(4)mim]PF6, [C(4)mim]Cl, [C(8)mim]Br, [C(8)mim]BF4, and [HOEtMIm]NT12. The nanostructures were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The results show that the morphologies of SrCO3 were strongly dependent on the nature of the corresponding RILs, its content, and the reaction temperature. RILs can act as structure-directing agent, leading the auto-assembly of SrCO3 crystal. [C(8)mim]BF4 and [HOEtMIm]NT12 favored the production of nanowhisker and nanospindle SrCO3, respectively, whereas [C(4)mimp]PF6 favored the production of nanosphere. Small particles were obtained at high reaction temperature. Low starting decomposition temperature was observed. Finally, the formation mechanism of the SrCO3 crystal was preliminary presented. (C) 2012 Elsevier Ltd. All rights reserved

Facile synthesis of SrCO3 nanostructures in methanol/water solution without additives

Highly dispersive strontium carbonate (SrCO3) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N-2 adsorption-desorption. The results showed that the reaction temperature and the methanol/water ratio had important effects on the morphologies of SrCO3 particles. The dumbbell-like SrCO3 exhibited a Broader-Emmett-Teller surface area of 14.9 m(2) g(-1) and an average pore size of about 32 nm with narrow pore size distribution. The formation mechanism of the SrCO3 crystal was preliminary presented

Preparation of nano-sized calcium carbonate in solution mixing process

Discreet nano-sized precipitated calcium carbonate was prepared by a simple solution mixing process, in which sodium carbonate solution was injected into calcium chloride solution containing calcium hydroxide. The morphology, size, and structure of the as-prepared precipitated calcium carbonate and intermediate products were examined. The results indicated that the non-impurity additive of calcium hydroxide, temperature below 30 degrees C, and controlled injecting rate were essential to obtain nano-sized precipitated calcium carbonate in the solution mixing process. It was observed that the intermediate nanofibrils fragged into nanograins in the process. This method can provide a simpler method to study the formation mechanism of nano calcium carbonate

<b>Facile synthesis of CdS nanocrystals using thioglycolic acid as a sulfur source and stabilizer in aqueous solution</b>

A novel method has been developed for the synthesis of CdS nanocrystals (NCs) using thioglycolic acid (TGA) as a sulfur source and stabilizer with the presence of hydrogen peroxide in an aqueous medium. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the product was of zinc-blend crystal structure in a sphere-like shape. The room-temperature luminescence spectra revealed that the emission peak of CdS NCs prepared in relatively short refluxing times (10-120 min) could be tuned from 518 nm to 610 nm, and the photoluminescence quantum yield of the as-prepared CdS NCs could reach as high as 12.6%. In addition, the mechanism of the CdS nanocrystals formation was preliminarily discussed