Search query: synthesis, properties of semi conductor  nano materials

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abstract: Abstract The synthesis of CdS nano particles have been widely studied for their potential usage in the field of optics. The Semi conductor nanoparticles doped with transition metal ions have attracted a wide attention due to their excellent luminescent properties. The transition metal doped nano particles have different optical properties corresponding to their host counter parts. These nano particles have tremendous applications in the fabrication of optical light emitting diodes and to design a suitable window material in fabrication for solar cells. The microwave assisted solvothermal method is used to prepare the nano particles in this study. The nano structured materials of CdS were characterized by XRD and UV techniques. The size of the crystallite is determined by XRD to be 18.26 nm depending on the amount of the molar ratio of the reactants present in the sample. The nanocrystalline nature of CdS particles and the diffused pattern shows the presence of hexagonal phase in the present system. The quantum size dependent effect and the optical quality of the CdS and Mn doped CdS are studied. The optical absorption and transmitance spectrum of the Pure and Mn doped CdS nanocrystals are synthesized in this work. CdS is a commercially important II VI semiconductor having wide optical band gap, rendering it a very attractive material for optical application especially in nanocrystalline form. The UV absorption edge provides a reliable estimate of the band gap of any system. It is found that the band gap of the pure CdS nanosystem in the present study is 2.45 eV and this value is found to be larger than that of bulk CdS. This variation of the band gap may be useful to design a suitable window material in fabrication for solar cells. In optoelectronics, it finds use as light emitting diode, reflector, dielectric filter and window material.
author_names: S Rinu Sam

Fergy John
title: Optical properties of pure and doped CdS nanoparticles under solvothermal method
year: 2020

abstract: The emerging need of CuS and Transition metal sulfides have numerous applications in various fields made its synthesis needful and meaning full. In recent years there is increasing interest in semiconductor nano crystals due to their novel physical and chemical properties. Most of these sulfides are crystalline and exhibit high lubricities. These features make these sulfides a far better photoluminescent material as compared to oxides. Many sulfides exhibit semi metallic behavior with respect to the ability to form multiple oxidation states, thus they are applicable in microelectronics as semiconductor materials.The emerging need of Cd and CdS nanoparticles in the medicine and many other fields made its synthesis needful and meaning full. For example CdS is an important semiconductor and has many optoelectronic applications including Solar cells, photodiodes, light emitting diodes, nonlinear optics and heterogeneous photo catalysis. In the present study we have synthesized CdS nanoparticles of chemical precipitation technique. CdS is an important inorganic material for light emitting applications. The literature survey showed that there are numerous methods to prepare Cadmium Sulfide (CdS) nanoparticles. To our knowledge, there is no report of synthesis of Cadmium sulfide nanoparticles by using SLS as a capping agent. So we have planned to synthesis the CdS nanoparticles by using SLS as a capping agent and to characterize the product by various analytical methods. Such The particles are characterized using FTIR, XRD, SEM, and Antimicrobial activity.
author_names: S Priscilla Prabhavathi

Shameela Rajam
title: MICROWAVE SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL ACTIVITIES OF CuS AND CdS NANO PARTICLES
year: 2014

abstract: Infra red (IR) luminescent quantum dots (QDs) are predominantly based on PbS or PbSe. However, while being attractive materials for solar energy conversion and photodetection, their long radiative lifetime and 8 fold degenerate HOMO and LUMO states make them less interesting for light emission applications. An alternative is offered by the mercury chalcogenides HgX (X=Se, Te) These materials are semi metals in the bulk, yet when the crystal dimensions are confined to nano scale regime, a band gap is opened up which can be tuned in the entire infra red range. While mainly studied in view of photodetection, the lower degeneracy of their band edge states and their shorter radiative lifetime as compared to PbS and PbSe makes them appealing for light emission too. A key step to make quantum dots fit for lighting application proved to be the formation of core shell QDs, where the shell provides a better surface passivation and allows for a further tuning of the opto electronic properties. However, while a broad range of shell growth procedures have been developed for Zn, Cd and Pb chalcogenide QDs, literature shows little examples of HgX based core/shell QDs of use of light emission applications. Here, we demonstrate the formation of HgSe/CdS and HgSe/CdSe core/shell QDs and report on the opto electronic properties of the materials thus formed. With lattice parameters of 0.608 (HgSe, CdSe) and 0.582 nm (CdS) and similar zinc blende crystal structures, CdSe and CdS are ideal shell materials to form HgSe based core/shell structures with minimal lattice strain. Considering the excessive ripening of HgSe QDs at typical shell growth temperatures, we developed a room temperature colloidal ALD procedure. As confirmed by electron microscopy, this results in the layer by layer growth of both CdSe and CdS around the HgSe core, with the QD diameter increasing by 0.6 nm per cycle. While growing up to 5 CdS and CdSe shells, we found that especially the first CdSe and CdS layers lead to a considerable redshift of the band edge transition and eliminate the n type doping of as synthesized HgSe QDs. This results in core/shell QDs showing bright photoluminescence in the near infrared, ranging from the telecom wavelengths of 1300 and 1550 nm to the longer wavelengths of interest for IR spectroscopy.
author_names: Laxmi Chiluka

Pieter Geiregat

Willem Walravens

Zeger Hens
title: Synthesis of novel HgSe/CdS and HgSe/CdSe core shell nanocrystals by C ALD approach in the infra red
year: 2015

abstract: For the past few years, the prepration and characterization of nanocrystals of materials have become an interesting area in the research activity. CdS (Cadmium Sulphide) is a well known semi conducting material which finds applications in optical devices. In the present study, we have made an attempt to investigate the effect of Pb as impurity on the properties of CdS nanocrystals. The samples were prepared by using simple domestic microwave assisted solvothermal method with ethylene glycol as solvant. The samples prepared were annealed to have good ordering. X ray diffraction measurements were carried out for all the smples. The grain size, lattice parameter and yield were determined. The colour before and after annealing was noted. EDX and SEM analyses were also done. The prepared samples were electrically characterized by making dielectric measurements on the prepared pellets. The present study indicates that the polarization mechanism in the nano crystals considered is mainly contributed by the space charge polarization.
author_names: K U Madhu
title: SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF CDS NANOCRYSTALS ADDED WITH PB2
year: 2013

abstract: Abstract The article describes the synthesis of solid solutions of ZnS CdSe, ZnS CdS, ZnS ZnTe systems (for the first time in the given compositions) Through X ray, IR spectroscopic and electron microscopic studies, the findings about their bulk physicochemical properties were obtained. These data can be used for certification and determination of their structures. It was determined that solid substitution solutions with preliminary hexagonal structures are formed. According to the results of the acid base properties investigation, the surfaces of all stated systems components exposed to air have slightly acid nature and offer the increased activity against the basic gases. Generally, the coordinatively unsaturated atoms account for the surfaces acidity. The interrelated laws were found in changing of the acid base and most essential bulk physicochemical properties on modifying the composition of the series of analogues ZnBIV, CdBIV and the solid substitution solutions formed by them. These laws likely connected to the electron structure of the non metallic components are used to find the most active adsorbents, primary transducer materials of the sensors for basic gases micro impurities.
author_names: I A Kirovskaya

Ekaterina Mironova

V E Leonov

B A Kosarev

A A Grigan

A V Yureva
title: The activity of new materials surfaces ternary semi conductors with cationic and anionic substitution
year: 2015

abstract: Abstract In the present contribution a simplistic synthesis of SnO 2 thin film on ultrasonically cleaned soda lime glass is outlined. Precursor solution of strength 0.1 M, 0.2 M and 0.3 M are used for the synthesis using a homemade affordable spray pyrolysis technique. An elaborate structural analysis is carried from the X Ray diffraction data. The structural analysis is supported by the transmission electron microscopy micrograph and selected area electron diffraction pattern. The crystallite sizes are below 50 nm that makes the films suitable for nano material application. Formation of texture is observed which indicates the preferred orientation to be the (101) plane. In comparison to techniques like pulsed laser deposition, spray pyrolysis provides better results for certain applications. The morphology of the thin films is investigated using atomic force microscopy. It revealed the control of application dependent roughness of the sample by variation of molarity of the precursor solution. Also the film is uniformly spread throughout the substrate. The optical properties are studied by UV Visible spectroscopy that further confirms formation of nano structures. Preliminary electrical investigation of the thin films is done by using a two probe semi conductor characterization system and is correlated with UV Visible result. Impedance analysis showed that with higher molarity the impedance remains constant and the barrier height remains fixed for high frequency which predicts that the films can be used for rectifying applications.
author_names: Sandip Paul Choudhury

Sneha Gunjal

Navnita Kumari

Kiran Diwate

Kakasaheb C Mohite

Ayon Bhattacharjee
title: Facile synthesis of SnO2 thin film by spray pyrolysis technique, investigation of the structural, optical, electrical properties
year: 2016

abstract: Silver tellurides are found as minerals like hessite (Ag2Te) and empressite (AgTe) They possess interesting physical properties including transition from semi to ionic conductor character and large magnetoresistance in non stoichiometric compounds. Silver tellurides exhibit high electron mobility and low thermal conductivity which are desirable for thermo electronics, finding applications in infrared detection, imaging, magnetics, sensors, memory devices and optic materials. Laser desorption ionisation time of flight mass spectrometry (LDI TOF MS) is powerful technique to follow the generation of clusters from various solid materials. In this work new nano composite consisting of nano silver and tellurium has been prepared and characterized by XPS, SEM, AFM, etc. The use of this material for surface enhanced Raman resonance scattering (SERRS) was evaluated. Furthermore, the nano composite was used as a precursor for laser ablation synthesis (LAS) of novel AgpTeq clusters analysed by TOF MS. In addition, oxygenated silver tellurium clusters with general formula AgpTeqOr were also detected. Stoichiometry of all generated clusters was determined via computer modeling. On the basis of new structural silver tellurium motifs novel high tech materials are proposed.
author_names: Filippo Amato

Ravi Madhukar Mawale

Milan Alberti

Josef Havel
title: Generation of mixed AgpTeq clusters via laser ablationsynthesis using novel Ag Te nano composite as precursor.Time of flight mass spectrometric study
year: 2014

abstract: Since their discovery in 2004, carbon dots have emerged out as a new class of material with a number of attractive physicochemical properties like fluorescence fair water solubility non toxicity, biocompatibility, chemical stability etc. Owing to these excellent properties, carbon dots (CDs) have potential to be used in bio imaging bio sensing, drug delivery catalysis etc. Recently, we have reported water absorption and moisture permeation behavior of chitosan/carbon dot Nano composite films and observed that carbon dots act as an effective cross linker due to electrostatic interactions between negatively charged carboxylate groups on the surface of carbon dot and positively charged NH3+ groups along the protonated chitosan chains. It was observed that water absorption of chitosan/carbon dots nanocomposite films decreased many folds as compared to the plain chitosan films. This led us to believe that incorporation of carbon dots into drug loaded chitosan film could bring about a desirable release of entrapped bioactive ingredient in a controlled manner. Chitosan is a semi synthetic polymer, obtained from a controlled de acetylation of chitin .Because of excellent biocompatibility; chitosan has a wide range of biomedical applications. Since carbon dot also possess fair biocompatibility, a combination of pre calculated quantities of chitosan and carbon dot could serve as an effective dressing material to offer a controlled release of drug in wound healing management. In the present work, we have prepared carbon dots from 1, 2, 3, 4 Butane tetra carboxylic acid via microwave synthesis approach. The CD, so prepared, had their surface covered with COOH groups. Then we entrapped these functionalized CD along with model antibacterial drug Oxy tetracycline (OTC) in chitosan film by solution casting method. The release of drug OTC from the film matrix could be regulated by varying the CD concentration within the film matrix as CD provided physical crosslinking to the chitosan network. Therefore, variation in the CD contents within the film matrix could regulate the release rate of OTC. In this way, without using toxic chemical crosslinking agents, a controlled release of OTC from chitosan films could be achieved.
author_names: Katta Eswar Srikanth
title: Oxytetracycline Drug Release Behavior
year: 2020

abstract: Zinc oxide (ZnO) has a wurtzite structure, a characteristic of semi conductors, and is used in electronic ceramic devices [1, 2] and photo catalysts [3, 4] Nanoscale particles possess different physical and chemical properties compared to bulk materials. Better sinterability, higher catalytic activity, and other unique properties may be expected because of their nano sized crystallite, large surface area and different surface properties (such as surface defect) etc. At present, two methods are generally being used to obtain nanosized ZnO powder: vapor method and sol gel method, which require high processing and chemicals costs, respectively [5] Therefore, the synthesis method of nano sized ZnO powders can still be improved. Recently, several researchers proposed the solution combustion method to synthesize simple and mixed metal oxides [6 11] Using this method, the heating and evaporation of metal nitrate solution with an organic compound (such as glycine, urea, or citric acid etc. results in self firing and generates intense heat by exothermic reaction. This intense heat is used to synthesize the ceramic powders. This novel approach has the advantages of inexpensive raw materials, a relatively simple preparation process, and a fine resulting powder with high homogeneity. Although there is little literature reporting that nanosized ZnO have been synthesized by this method [4, 5, 12, 13] there is also hardly any information available on the effects of reactant composition in the nature of combustion reaction phenomena on the properties of as synthesized ZnO powders. In this work, the study of correlation among reactant composition, reaction phenomena, and product characteristics are undertaken. Glycine (NH2CH2COOH) was selected as the fuel since it is inexpensive and its combustion heat 3.24 Kcal/g) is more negative when compared with urea 2.98 Kcal/g) or citric acid 2.76 Kcal/g) On the other hand, zinc nitrate [Zn(NO3)2*6H2O] is utilized in the present work because of its dual role of being the zinc source and the oxidant. The combustion reaction can be expressed (but over simplified) as follows:
author_names: Chyi-Ching Hwang

Tsung-Yung Wu
title: Combustion synthesis of nanocrystalline ZnO powders using zinc nitrate and glycine as reactants influence of reactant composition
year: 2004

abstract: Abstract The present work describes the realization of inorganic semi conducting compounds in the form of a monomolecular plane, generated from an L.B. matrix. Mercury and cadmium sulfides are obtained by a two step, in situ synthesis, from the organic molecules of an L.B. film: multilayers of behenic acid are transformed into cadmium or mercury behenate by an aqueous diffusion of each ion. Next, a gaseous diffusion of hydrogen sulfide precipitates the HgS or CdS in the polar plane with regeneration of the behenic acid matrix. These chemical reactions are followed by infrared spectroscopy. The observed photoelectric properties in the near U.V. range argues in favour of a) a monomolecular plane of a semiconducting sulfide. b) a 2D structure of the sulfides, different from the known 3D crystals of HgS and CdS which absorb in the visible and infrared range. Hence it can be assumed that the 2D sulfide synthesis is matrix controlled, since the physical properties are different. This opens the field for new monomolecular materials because this experiment can be enlarged to other compounds.
author_names: Cecile Zylberajch

Annie Ruaudel-Teixier

Andre Barraud
title: 2D monomolecular inorganic semi conductors, inserted in a Langmuir Blodgett matrix
year: 1988