Search query: Doped semiconductor nanoparticles synthesized in gas-phase plasmas 

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abstract: Crystalline nanoparticles (NPs) of semiconductor materials have been attracting huge research interest due to their potential use in future applications like photovoltaics and bioimaging. The important role that intentional impurity doping plays in semiconductor technology has ignited a great deal of research effort aiming at synthesizing semiconductor NPs doped with foreign impurities and at understanding their physical and chemical properties. In this respect, plasma grown semiconductor NPs doped in situ during synthesis have been key in studies of doped NPs. This article presents a review of the advances in understanding the properties of doped semiconductor NPs synthesized by means of plasma methods and the role played by these NPs for our current understanding of doped NPs and the general behavior of doping in nanoscale materials.
author_names: Rui N Pereira

A J Almeida
title: Doped semiconductor nanoparticles synthesized in gas phase plasmas
year: 2015

abstract: Abstract A series of semiconductor photocatalysts based on transition metals (M' V, Cr, Fe, Co, Mn, Mo, Ni, Cu, Y, Ce, and Zr) incorporated TiO2 (Ti/M' 20 atomic ratio) materials have been synthesized by adopting a one step liquid flame aerosol synthesis technique. The resulting materials were explored for the destruction of acetonitrile in gas phase under visible light irradiation at ambient conditions. Our H2 TPR studies revealed the formation of Me O Ti bonds, which suggest the strong interaction of dopant metal TiO2 in all the as synthesized materials. The reduction peaks in Cr doped TiO2 shifted to much lower temperatures, due to the increase in the reduction potential of titania and chromium. The strong interaction (formation of Cr O Ti bonds) is the main reason that the Cr/TiO2 is an active photocatalyst in visible light. Our XPS studies suggest that the relative atomic percentage value of Ti3+/Ti4+ characterized by XPS was significantly high for our flame made Cr/TiO2 nanoparticles (Ti3+/Ti4+ 0.89, 32.9% whereas, other samples demonstrated poor atomic percentage value of Ti3+/Ti4+ (Ti3+/Ti4+ 0.08 0.32) The existence of Ti3+ species with narrow band gap is highly beneficial for the promotion of visible light induced photocatalytic activity. The position of the Cr 2p peaks shifted to lower binding energies in Cr doped TiO2 nanoparticles. The electrons migrate from the TiO2 nanoparticles to chromium species, which reveals a strong interaction between Cr and TiO2 nanostructure in the interface of flame made nanoparticles. Conversely, Mn3+ species combined with TiO2 because its surface metal dispersion was kept high after TiO2 loading. However, Mn3+ incorporated catalyst was inactive because of the small energy driving force for electrons to detrap from Mn2+ The UV vis spectroscopy results of M' doped TiO2 (M' Fe, Cr, V, Co, Ce, and Ni) materials showed augmentation of light absorption in the visible range. The Cr, V and Fe (Ti:M' atomic ratio 20:1) titania aerosol catalysts reduced the bandgap energy of TiO2 to 2.9 eV under visible light irradiation. Among all of the catalysts we tested, the transition metals (M' Cr, Fe, and V) incorporated materials have shown an impressive catalytic performance in visible light. Among all the catalyst tested, Cr doped titania demonstrated a superior catalytic performance and the rate constant is about 8 19 times higher than the rest of the metal doped catalysts. Their catalytic performances are correlated with the UV vis spectrum of each synthesized catalyst to reveal the specific role played by each metal ion.
author_names: Siva Nagi Reddy Inturi

Thirupathi Boningari

Makram Tewfik Suidan

Panagiotis G Smirniotis
title: Visible light induced photodegradation of gas phase acetonitrile using aerosol made transition metal (V, Cr, Fe, Co, Mn, Mo, Ni, Cu, Y, Ce, and Zr) doped TiO2
year: 2014

abstract: Abstract Aluminum doped ZnO (AZO) nanoparticles are studied widely as transparent conducting alternatives for indium tin oxide. However, the properties of AZO vary in different investigations not only with the amount of dopant and the particle size, but also with other parameters such as synthesis method and conditions. Hence, AZO nanoparticles, synthesized in the gas phase, were investigated to study the influence of the synthesis parameters dopant level, reactor temperature and residence time in the reaction zone on the particle characteristics. The local structure of the dopant in semiconductors determines whether the doping is functional, i.e. whether mobile charge carriers are generated. Therefore, information obtained from 27Al solid state NMR spectroscopy, X ray diffraction, photoluminescence and UV Vis spectroscopy was used to understand how the local structure influences particles characteristics and how the local structure itself can be influenced by the synthesis parameters. In addition to AZO particles of different Al content, pure ZnO, Al2O3, ZnAl2O4 and core shell particles of ZnO and Al2O3 were synthesized for comparison and aid to a deeper understanding of the formation of AZO nanoparticles in the gas phase.
author_names: Carolin Schilling

Manfred Zahres

Christian Mayer

Markus Winterer
title: Aluminum doped ZnO nanoparticles: gas phase synthesis and dopant location
venue: Journal of Nanoparticle Research
year: 2014

abstract: Abstract The plasma chemical solvent free method of doped and nanocomposite polyaniline based (PANI based) conductive coatings deposition was elaborated. Molecular structure, morphology, optical, electrical and sensing properties of PANI based coating were investigated by Fourier transform infrared, UV vis, impedance spectroscopy methods and transmittance electron microscopy. The synthesized PANI based coatings containing silver nanoparticles have a partially doped structure with low variation in size of oxidized and reduced PANI units. The nanocomposite PANI based coatings were deposited onto interdigital capacitor for ammonia gas sensing applications. The increasing of the sensing performance of the PANI based coatings with silver nanoparticles was established in particular at the low frequency region of impedance spectra. The high sensitivity and linearity of this sensor response were examined at a direct and alternating voltage with ammonia concentrations up to 10 ppm.
author_names: A A Ragachev

Maxim A Yarmolenko

Jiang Xiaohong

Rui-qi Shen

Petr A Luchnikov

A V Rogachev
title: Molecular structure, optical, electrical and sensing properties of PANI based coatings with silver nanoparticles deposited from the active gas phase
year: 2015

abstract: In this study, we synthesize europium doped Ag2S diluted magnetic semiconductor (DMS) nanoparticles using a gas liquid phase chemical deposition process. It has been found that the Ag2S:Eu nanoparticles have room temperature ferromagnetism (RTF) and display two remarkable magnetic phase transitions with decreasing temperature, i.e. the classic thermally driven transition from superparamagnetism to blocked superparamagnetism and the quantum phase transition from magnetic long range order to quantum superparamagnetism state. When the blocking temperature (TB, 300 K) is reached, the first magnetic phase transition from superparamagnetism to blocked superparamagnetism is observed; after further temperature decrease to the critical phase transition temperature (TC, 11 K) the second magnetic phase transition which is from magnetic long range order to quantum superparamagnetism is observed because of the quantum tunnelling effect. The spin resolved density of states is calculated by the software VASP (Vienna Ab initio Simulation Package) to investigate the origin of magnetism of the Ag2S:Eu nanoparticles. It is found that the magnetism originates from the doped Eu atoms and is caused by an f f exchange interaction of Eu ions.
author_names: Tianye Yang

Heung-Mo Yang

Pan Wang

Rui Zhao

Chuanhai Xiao

Shuangming Wang

Bingxin Xiao

Zhifang Li

Mingzhe Zhang
title: Magnetic phase transition of Ag2S:Eu diluted magnetic semiconductor nanoparticles
year: 2014

abstract: SiGe alloys belong to the class of classic high temperature thermoelectric materials. By the means of nanostructuring, the performance of this well known material can be further enhanced. Additional grain boundaries and point defects added to the alloy structure result in a strong decrease in thermal conductivity because of reduced lattice contribution to the overall thermal conductivity. Hence, the figure of merit can be increased. To obtain a nanostructured bulk material, a nanosized raw material is essential. In this work, a new approach toward nanostructured SiGe alloys is presented where alloyed nanoparticles are synthesized from a homogeneous mixture of the respective precursors in a microwave plasma reactor. As prepared nanoparticles are compacted to a dense bulk material by a field assisted sintering technique. A figure of merit of zT 0.5 0.09 at 450 degC and a peak zT of 0.8 0.15 at 1000 degC could be achieved for a nanostructured, 0.8% phosphorus doped Si 80 Ge 20 alloy without any further optimization.
author_names: Niklas Stein

Nils Petermann

Ralf Theissmann

Gabi Schierning

Roland Schmechel

Hartmut Wiggers
title: Artificially nanostructured n type SiGe bulk thermoelectrics through plasma enhanced growth of alloy nanoparticles from the gas phase
year: 2011

abstract: Abstract ZnS nanoparticles with Ni 2+ as dopant ions, have been synthesized and characterized by X ray Diffraction, Inductive Coupled Plasma Atomic Emission spectroscopy and Transmission Electron Microscopy. UV vis absorption and photoluminescence spectroscopies were employed to investigate different photo processes occurring on exposure to UV vis light. The synthesized NPs were evaluated as photocatalyst for the removal of the color of aqueous solution of rhodamine B (RhB) dye as test solution under 250 W High Pressure Mercury Vapor lamp. Mott Schottky, Cyclic Voltammetery, and hot probe measurements suggest the change in the 'type' of semiconductor from n to p as well as phase change (cubic to wurtzite) take place on increasing the amount of dopant to 10% The newly appeared phase forms 'local pockets' in an overall cubic matrix of ZnS NPs, this way created defects at the local grain boundaries of dissimilar phases. These provide active sites for the adsorption of dye molecules, in turn, improve the efficiency of the material as photocatalyst.
author_names: Ekta Shah

Jayraj V Vaghasiya

Saurabh S Soni

C J Panchal

Priyanka Suryavanshi

Mukesh M Chavda

Hemant P Soni
title: Ni doped ZnS nanoparticles as photocatalyst: Can mixed phase be optimized for better performance?
year: 2016

abstract: The one step synthesis of oleic acid coated TiO2 nanoparticles with visible light driven photocatalytic activity was reported by this manuscript, using oleic acid ethanol as crucial starting materials. The photocatalytic degradation of nitrogen monoxide (deNOx) in the gas phase was investigated in a continuous reactor using a series of TiO2 semiconductors, prepared from oleic acid or acetic acid ethanol solution. The surface modification on TiO2 by organic fatty acid, oleic acid, could reinvest TiO2 photocatalyst with the excellent visible light response. The deNOx ability is almost as high as 30 destruction in the visible light region (l 510 nm) which is similar to the nitrogen doped TiO2. Meanwhile, acetic acid, a monobasic acid, has a weaker ability on visible light modification of TiO2.
author_names: Huihui Li

Bin Liu

Shu Yin

Tsugio Sato

Yuhua Wang
title: Visible Light Driven Photocatalytic Activity of Oleic Acid Coated TiO2 Nanoparticles Synthesized from Absolute Ethanol Solution
venue: Nanoscale Research Letters
year: 2015

abstract: Author(s) Bonabi Naghadeh, Sara Advisor(s) Zhang, Jin Z Abstract: Nanomaterials including metals, metal oxide, and semiconductors have been studied as powerful tools for various applications including photovoltaic, photocatalyst, biomedical therapeutics, sensing, energy storage, wastewater treatment and so many more. Based on the specific application, these nanomaterials can be tuned and optimized to achieve their best performance. These modifications can be in the form of altering size, shape, crystal structure, surface passivation, surface morphology, and doping. In this dissertation, the effect of size and surface modification on optical, photophysical and photocatalytic properties of perovskite nanocrystals, CdS based nanocomposites, and hollow gold nanoparticles are investigated. In chapter 1, a comprehensive literature review was done on photophysical properties and improved stability of organic inorganic perovskite nanomaterials by surface passivation. In this chapter, it is discussed how by changing the capping ligand and surface passivation strategies, the size, shape and crystal structure of these nanomaterials were controlled to produce high quality nanostructured and bulk film perovskites. The degradation mechanism and surface passivation approach to address the instability issue toward environmental factors were also highlighted. This information emphasizes the importance of defect passivation and surface modification in achieving high performance in photovoltaic applications.In chapter 2, a new surface passivation strategy was developed using peptide molecules with amine and carboxylic functional groups to synthesize methylammonium lead bromide (CH3NH3PbBr3) perovskite nanocrystals (PNCs) with excellent optical properties. It was demonstrated in this work that well passivated PNCs can only be obtained when both amino and carboxylic groups were involved, and this is attributed to the protonation reaction between NH2 and COOH. In addition to their improved optical properties, using peptide as capping ligand resulted in increasing the product yield up to ~44% This is due to the polar nature of peptides, which cause aggregation and precipitation of peptide passivated PNCs from nonpolar toluene solvent. PNCs size was also controlled by adjusting the concentration of the peptide, resulting in tunable optical properties due to the quantum confinement effect. Furthermore, generality and versatility of this strategy were shown by passivating different types of PNCs such as CsPbBr3. In chapter 3, three differently sized (3.1, 5.7, and 9.3 nm) methylammonium lead bromide (CH3NH3PbBr3) perovskite nanocrystals (PNCs) were synthesized using (3 Aminopropyl) triethoxysilane (APTES) and oleic acid (OA) as capping ligands. The size dependence of charge carrier dynamics was studied to decipher the radiative and non radiative components. These PNCs showed size dependent absorption and photoluminescence (PL) with the middle sized PNCs exhibiting the highest PL quantum yield ~91% The effect of size on the exciton/charge carrier dynamic of PNCs was studied using transient absorption spectroscopy (TA) and time resolved photoluminescence (TRPL) The middle sized PNCs (PNC35_APTES) showed slower early time recombination compared to that of the larger and smaller PNCs, suggesting optimized passivation of surface trap states. However, the radiative lifetime was found to decrease with decreasing PNC size, which seems to be primarily determined by the PNC core, while the non radiative lifetime is longest for the middle sized PNCs, which is strongly influenced by the presence of bandgap states that depend on surface passivation. A kinetic model is proposed to explain the observed dynamics results, including size dependence. This study demonstrates the competing effect between size and surface properties in determining the dynamics and optical properties of PNCs. In chapter 4, the same three differently sized methylammonium lead bromide (CH3NH3PbBr3) perovskite nanocrystals (PNCs) were studied using UV Vis, photoluminescence (PL) temperature dependent PL, temperature dependent time resolved PL (TRPL) cryo XRD, and cryo EM to investigate crystal phase stability of the PNCs as a function of size at different temperatures ranging from 20 K to 300 K. The preliminary results showed a spectral blue shift of the PL peak by decreasing the temperature, which is the opposite of what was observed for large and middle sized particles. The lifetime of the smaller PNCs also decreased by increasing the temperature. These results can be possibly due to crystal phase transition in the small particles. Future work is suggested to further investigate the phase transition possibility using cryo XRD at slow scanning rate and temperature dependent Raman spectroscopy. In chapter 5, different compositions of CdS nanowires with MoS2, NiS, NiS2, Ni3S2, and NiCo2S4 nanoparticles composites were synthesized and the photocatalytic activities of them in hydrogen evolution reaction (HER) was investigated. These hierarchical structures provide high activation potentials for HER and suppress the photo corrosion of CdS. The results indicated there is an optimal amount of nanoparticles decorated on the CdS surface for optimized performance. This optimum nanoparticle ratio will provide uniform coverage of the CdS surface resulting in efficient charge transfer. While the higher ratios form aggregate structures, which act as carrier trap states. To gain deeper insight into the mechanism behind the enhanced performance, ultrafast transient absorption (TA) techniques were used to probe the charge carrier dynamics of these CdS based heterostructures. At the for each nanocomposite, mechanism of charge transfer between components was proposed. In chapter 6, the effect of targeting on photothermal therapy (PTT) efficiency of hollow gold nanoparticles (HGNs) was investigated. HGNs are class of plasmonic nanomaterials which showed great potential for biomedical applications and specifically PTT. These HGNs can be easily modified on the surface and be conjugated to various targeting ligands including antibody, peptide and other small molecules such as folate. In this chapter, HGNs with an average outer diameter of 40 nm were synthesized and conjugated to anti_EGFR antibody and GE 11 peptide, which both target EGF receptors on cancer cells. The conjugated HGNs were characterized using UV Vis, photoluminescence (PL) Inductively coupled plasma optical emission spectrometry (ICP_OES) bicinchoninic acid assay (BCA) fluorescence microscopy, and confocal microscopy. The preliminary results showed significantly higher cell death with peptide conjugated HGNs (91% compared to antibody conjugated HGNs (54% Different hypotheses were discussed as a possible explanation for this enhanced PTT efficiency including possible particle internalization, better binding to receptors due to small ligand size, and most importantly closer proximity of HGNs to the cell surface resulting in more efficient heat transfer.
author_names: Sara Bonabi Naghadeh
title: Synthesis, Surface Modification and Photophysical Properties of Plasmonic Metal, Metal Oxide Nanoparticles, and Semiconductor Quantum Dots
year: 2019

abstract: There is an eminent interest to improve the photoactivity of TiO2 nanostructures via doping with mid band gap donors or acceptors to achieve a high solar absorption. In the present work, Cr and V doped TiO2 nanoparticles were prepared via a facile chemical vapor synthesis method. The effect of the transition metals (TM) on the solar light activity of the semiconductor nanoparticles as photocatalyst was examined by degradation of methylene blue and acid red 27. Induced coupled plasma and X ray photoelectron spectroscopy analyses indicated high efficiency of the doping process in the hot wall reactor without surface covering of the TiO2 nanoparticles by the dopants. Diffuse reflectance spectroscopy also revealed a red shift of the absorption edge of the TiO2 nanoparticles with increasing dopant concentration. Analysis of the photoactivity of the synthesized nanoparticles under sun light showed an increase in the primary absorption of dye molecules on the surface of Cr and V doped TiO2 nanoparticles whereas the degradation rate was found to depend on the type and concentration of the dopants. A high photoactivity is obtained at 0.2 at% V concentration. The mechanism of photoactivity is discussed based on the effect of TM on the absorption edge of the semiconductor.
author_names: Nasser Khakpash

Abdolreza Simchi

Tahereh Jafari
title: Adsorption and solar light activity of transition metal doped TiO2 nanoparticles as semiconductor photocatalyst
venue: Journal of Materials Science: Materials in Electronics
year: 2011