Simple Aqueous Chemical Method Research Articles

Low thermal conductivity and enhanced Seebeck coefficient in Antimony and Selenium co-doped PbTe Nanopowders

We report a new method to synthesize Sb and Se co-doped PbTe nanopowders by a simple aqueous chemical method without the assistance of any surfactant or template. X-ray diffraction studies revealed that the prepared nanopowders are polycrystalline in nature and crystallize in the face-centered-cubic (fcc) PbTe structure. SEM and TEM studies reveal that Sb and Se co-doped PbTe nanopowders consist of an interconnected network of spherical nanoparticles with diameters around 12 nm. Seebeck coefficient of the undoped PbTe (436 µV/K at 301 K) and co-doped PbTe (627 µV/K at 301 K) is enhanced compared to that of the bulk PbTe (265 µV/K at 298 K) and the thermal conductivity is drastically decreased [undoped PbTe (0.265 W/m-K) and co-doped PbTe (0.525 W/m-K) at 378 K] compared with the value for the bulk PbTe (2.2 W/m-K at 300 K). The dimensionless figure of merit ZT attains its maximum value 0.055 at 378 K for undoped and 1.09 × 10−5 at 352 K for co-doped PbTe.

Study of ultraviolet sensing properties of ZnO nanoparticles grown on cellulose fibers

Abstract ZnO nanoparticles were grown on cellulose fiber surfaces with different precursor concentrations by a simple aqueous chemical method. The morphology and structure of the ZnO-cellulose nanocomposites were studied by scanning electron microscopy and X-ray diffraction, respectively. The ultraviolet sensitivity of the nanocomposites was observed by current-voltage measurement followed by time-resolved photocurrent study A ZnO-cellulose nanocomposite synthesized at 37.5 mM concentration of zinc nitrate hexahydrate had a higher UV sensitivity with faster response. Due to UV illumination, the photocurrent of the nanocomposite pellet increased from 2.251 × 10-8 A to 1.11 × 10-6 A in 8 s. The ON to OFF ratio (IUV/IDark) for this sample was found to be 49.31.

Self Powered Highly Enhanced Dual Wavelength ZnO@CdS Core-Shell Nanorod Arrays Photodetector: An Intelligent Pair.

On the face of the impending energy crisis, developing low-energy or even zero-energy photoelectronic devices is extremely important. A multispectral photosensitivity feature of a self-powered device provides an additional powerful tool. We have developed an unprecedented high performance dual wavelength self-powered ZnO@CdS/PEDOT:PSS core-shell nanorods array photodetector through a simple aqueous chemical method wherein a suitable band alignment between an intelligent material pair, i.e. ZnO and CdS, has been utilized. Besides a noteworthy advantage of the devices being that they show a very sharp and prominent dual wavelength photosensitivity, both the ultraviolet and visible light sensitivity (ratio of current under illumination (Iphoto)/current under dark (Idark)) of the device are two orders of higher magnitude than those of pristine ZnO, attaining values of 2.8 × 10(3) and 1.07 × 10(3), respectively. At the same time, temporal responses faster than 20 ms could be achieved with these solution-processed photodetectors. The present study provides a very important direction to engineer core-shell nanostructured devices for dual wavelength high photosensitivity.

α-S nanoparticles grown on MoS2 nanosheets: A novel sulfur-based photocatalyst with enhanced photocatalytic performance

A novel α-S/MoS2 composite with well dispersed α-S nanoparticles on MoS2 nanosheets was prepared by a simple aqueous chemical method. The combination of MoS2 with α-S not only extended light adsorption spectrum but also enhanced the separation efficiency of photoinduced charge carriers. In the α-S/MoS2 composite, MoS2 nanosheets served as a photocenter for absorbing solar light to generate more charge carriers, and worked as an excellent electron transporter to separate charge carriers. As a result, α-S/MoS2 composite exhibited much higher photocatalytic activity for degradation of methylene blue under both UV and visible light irradiation, compared with pure α-S. Our results might open up a promising way to develop novel and highly efficient α-S-based photocatalyst.

Cu doped CdS nanoparticles: A versatile and recoverable catalyst for chemoselective synthesis of indolo[2,3-b]quinoxaline derivatives under microwave irradiation

CdS and Cu doped CdS NPs has been obtained successfully using safe agents through a simple aqueous chemical method and characterized by XRD, TEM, SEM, EDAX, UV/VIS and ICP-AES. These investigations revealed that the particle size of the synthesized materials were uniformly distributed in the range of 2–4nm and confirm the Cu doping in the lattice of CdS NPs. These nanoparticles were exploited to study their catalytic activities toward the chemoselective synthesis of indolo[2,3-b]quinoxalines by the reaction of isatins with 1,2-diamines in ethylene glycol under microwave irradiation. The method showed remarkable selectivity for indolo[2,3-b]quinoxalines over 3-imino-isatin, spirobenzimidazole, and ring-opened quinoxalinone derivatives. The catalytic activity of Cu doped CdS NPs was found to be about 18-fold higher under microwave irradiation (MW) as compared to the conventional method. Nanocatalyst plays a dual role of catalyst as well as susceptor, and enhances the overall capacity to absorb MW in the reaction mixture. Doping of Cu promotes the activity and selectivity of CdS nanoparticles indicated by high TOF value with good chemoselectivity. The surface acidity of NPs was measured by FTIR spectra of chemisorbed pyridine. Simple workup, mild reaction conditions, low cost, easy separation, and reusability of the catalyst are some advantages of this method.