Direct bandgap materials based on the thin films of SexTe100 - x nanoparticles

In this study, we fabricated thin films of Se(x)Te(100 − x) (x = 0, 3, 6, 9, 12, and 24) nanoparticles using thermal evaporation technique. The results obtained by X-ray diffraction show that the as-synthesized nanoparticles have polycrystalline structure, but their crystallinity decreases by increasing the concentration of Se. They were found to have direct bandgap (E(g)), whose value increases by increasing the Se content. These results are completely different than those obtained in the films of Se(x)Te(100 − x) microstructure counterparts. Photoluminescence and Raman spectra for these films were also demonstrated. The remarkable results obtained in these nanoparticles specially their controlled direct bandgap might be useful for the development of optical disks and other semiconductor devices

High-energy ball milling technique for ZnO nanoparticles as antibacterial material

Nanoparticles of zinc oxide (ZnO) are increasingly recognized for their utility in biological applications. In this study, the high-energy ball milling (HEBM) technique was used to produce nanoparticles of ZnO from its microcrystalline powder. Four samples were ball milled for 2, 10, 20, and 50 hours, respectively. The structural and optical modifications induced in the ‘as synthesized’ nanomaterials were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and photoluminescence emission spectra (PL). SEM and TEM results show a gradual decrease in particle size from around 600 to ∼30 nm, with increased milling time. The initial microstructures had random shapes, while the final shape became quite spherical. XRD analysis showed ZnO in a hexagonal structure, broadening in the diffracted peaks and going from larger to smaller particles along with a relaxation in the lattice constant c. The value of c was found to increase from 5.204 to 5.217 Å with a decrease in particle size (600 to ∼30 nm). PL result showed a new band at around 365 nm, whose intensity is found to increase as the particles size decreases. These remarkable structural and optical modifications induced in ZnO nanoparticles might prove useful for various applications. The increase in c value is an important factor for increasing the antibacterial effects of ZnO, suggesting that the HEBM technique is quite suitable for producing these nanoparticles for this purpose

Effect of Composition on Electrical and Optical Properties of Thin Films of Amorphous GaxSe100−x Nanorods

We report the electrical and optical studies of thin films of a-GaxSe100−x nanorods (x = 3, 6, 9 and 12). Thin films of a-GaxSe100−x nanorods have been synthesized thermal evaporation technique. DC electrical conductivity of deposited thin films of a-GaxSe100−x nanorods is measured as a function of temperature range from 298 to 383 K. An exponential increase in the dc conductivity is observed with the increase in temperature, suggesting thereby a semiconducting behavior. The estimated value of activation energy decreases on incorporation of dopant (Ga) content in the Se system. The calculated value of pre-exponential factor (σ0) is of the order of 101 Ω−1 cm−1, which suggests that the conduction takes place in the band tails of localized states. It is suggested that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. On the basis of the optical absorption measurements, an indirect optical band gap is observed in this system, and the value of optical band gap decreases on increasing Ga concentration

Synthesis and characterization of nanoparticle thin films of a-(PbSe)100−xCdx lead chalcogenides

We report the synthesis of amorphous (PbSe)(100−x)Cd(x) (x = 5, 10, 15, and 20) nanoparticle thin films using thermal evaporation method under argon gas atmosphere. Thin films with a thickness of 20 nm have been deposited on glass substrates at room temperature under a continuous flow (50 sccm) of argon. X-ray diffraction patterns suggest the amorphous nature of these thin films. From the field emission scanning electron microscopy images, it is observed that these thin films contain quite spherical nanoparticles with an average diameter of approximately 20 nm. Raman spectra of these a-(PbSe)(100−x)Cd(x) nanoparticles show a wavelength shift in the peak position as compared with earlier reported values on PbSe. This shift in peak position may be due to the addition of Cd in PbSe. The optical properties of these nanoparticles include the studies on photoluminescence and optical constants. On the basis of optical absorption measurements, a direct optical bandgap is observed, and the value of the bandgap decreases with the increase in metal (Cd) contents in PbSe. Both extinction coefficient (k) and refractive index (n) show an increasing trend with the increase in Cd concentration. On the basis of temperature dependence of direct current conductivity, the activation energy and pre-exponential factor of these thin films have been estimated. These calculated values of activation energy and pre-exponential factor suggest that the conduction is due to thermally assisted tunneling of the carriers

Electrical Conductivity and Thermoelectric Power of a-Se80−x\text{}_{80-x}Ga20\text{}_{20}Tex\text{}_{x} (x=0,5,10,15 and 20) Thin Films

The dc conductivity and thermoelectric power of a-Se$\text{}_{80-x}$Ga$\text{}_{20}$Te$\text{}_{x}$ (x=0,5,10,15 and 20) thin films were reported in the present work. The free charge carrier concentration was calculated with the help of dc conductivity and thermoelectric power measurements. The calculated values of free charge carrier concentration were used to evaluate the free charge carrier mobility from which grain boundary potential was evaluated. The results are interpreted in terms of small polaron hopping, the structure of Se-Te and the grain boundary potential barrier

Synthesis and Characterization of Nanoparticle Films and Their Optical Properties

Thin films of Se35Te65−Ge (=0,3,6,9,12) nanoparticles were synthesized using thermal evaporation method. They were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and absorption and transmission spectra. XRD results show that these films are of amorphous nature, while SEM images show nanoparticles with average particle size around 30 nm. No significant changes are observed in morphology of the deposited films by changing concentrations of Te and Ge. The optical behaviors of these films have been studied using the absorption and transmission spectra in the spectral region 400–1100 nm. The absorption, extinction coefficients and refractive index were obtained and investigated in more detail. The optical band gap () values were also determined and are found to decrease from 0.83 to 0.69 eV by increasing the concentration of Ge from 0 to 12. The transmission spectra for the thin films of Se35Te65−Ge nanoparticles show strong absorption at wavelength less than 500 nm and become highly transparent at wavelength above 800 nm. No significant changes in the transmission spectra are observed by increasing concentration of Ge. These results might be useful for development of optical disks and other semiconducting devices based on these nanochalcogenides

Perovskite sensitized solar cell using solid polymer electrolyte

WOS: 000370306300072A perovskite sensitized solar cell (PSSC) comprising ethyl ammonium to-lead iodide (CH3CH2NH3PbI3) and solid polymer electrolyte have been successfully fabricated and reported in this paper. Perovskite was synthesized by direct deposition of equimolar CH3CH2NH3I and PbI2 in dimethylformamide (DMF) solution. It was further characterized using various experimental tools like XRD, UV-visible, SEM and EDAX. The fabricated PSSC showed a short circuit current density (J(sc)) = 1.16 mA/cm(2), open circuit voltage (V-oc) = 0.70 V, fill factor (FF) = 0.67 and efficiency (eta) = 0.75% at one sun condition. Comparative data between PSSC and dye sensitized solar cell (DSSC) are also discussed in this paper. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Department of Science and Technology project, Government of IndiaGovernment of India [DST/TSG/PT/2012/51-C]; Nanotechnology and Renewable Energy Research Laboratory, Jamia Millia Islamia, Central University, New Delhi, IndiaThis work was supported by Department of Science and Technology project (DST/TSG/PT/2012/51-C), Government of India, and Nanotechnology and Renewable Energy Research Laboratory, Jamia Millia Islamia, Central University, New Delhi, India

New class of lead free perovskite material for low-cost solar cell application

In this paper, we fabricate a new class of perovskite sensitizer material for photovoltaic application. This is not only low-cost perovskite material but also is a non-toxic material for solar cell as compared to the conventional materials used in PSC. Detailed procedure of synthesis of CH 3 NH 3 SnCl 3 material and its application in fabrication of PSC is presented in the article. Perovskite material i.e. methyl ammonium tin tri-chloride (CH 3 NH 3 SnCl 3 ) was prepared by direct deposition of equimolar concentration of CH 3 NH 3 Cl and tin chloride (SnCl 2 ) in dimethylformamide (DMF) solution. X-ray diffraction pattern (XRD) of the material confirms the formation of perovskite structure whereas, UV–vis absorption spectroscopy shows the absorption range of these material. Crystal formation of the perovskite is confirmed from the scanning electron microscope (SEM). A comparison of the crystal and powder form of perovskite material is discussed in depth in terms of structural, optical and electrical properties

Nano and micro structures produced from carbon rich fly ash as effective lubricant additives for 150SN base oil

Lubricant oils in cars engines are essential components for reducing friction and fuel consumption. The lubrication process can be improved by including effective additives. Carbon nanostructures have been recognized as excellent additives in lubricant oils. Amongst them carbon nanotubes (CNTs) produced from carbon rich fly ash, are found to have excellent tribological properties in the sunflower base oil. In this work, these CNTs along with other micro and nanostructures produced from carbon rich fly ash are tested as lubricant additives in the 150SN base oil. The impregnated oils with these additives are evaluated to reduce the friction between two metallic surfaces using the ball-on-disk tribometer. The obtained results showed that CNTs of fly ash have significantly reduced the frictional coefficient by around 25% at a concentration of 0.1 wt%. This result is much better than that of the other fly ash micro and nanostructures produced by sonication and ball milling techniques. It is also compared with that of a commercial multiwall CNTs and is found to be superior. The friction coefficient values are investigated as a function of load and temperature. Moreover, the rheological behavior is also studied for the pure and 0.1 wt% CNTs-impregnated oil. No significant changes are observed in the viscosity of the impregnated oil. The present CNTs of carbon rich fly ash have been proved to be effective additives for the 150SN lubricant oil, and might be useful for variety of lubricants. Keywords: Lubricant additives, CNTs of oil fly ash, 150SN base oil, Friction coefficien