Kinds Of Dopants Research Articles

Multifunctional hydroxyapatite nanoparticles for drug delivery and multimodal molecular imaging

Hydroxyapatite (HAp) is the most important constituent of biological tissues such as bone and teeth and exhibits several characteristic features. HAp nanoparticles (NPs) are good host materials and can be functionalized with various kinds of dopants and substrates. By endowing HAp NPs with desired properties in order to render them suitable for biomedical applications including cellular imaging, non-invasive and quantitative visualisation of molecular process occurring at cellular and subcellular levels becomes possible. Depending on their functional properties, HAp based nanoprobes can be divided into three classes, i.e., luminescent HAp NPs (for both downconversion and upconversion luminescence), magnetic HAp NPs, and luminomagnetic HAp NPs. Luminomagnetic HAp NPs are particularly attractive in terms of bimodal imaging and even multimodal imaging by virtue of their luminescence and magnetism. Functionalised HAp NPs are potential candidates for targeted drug delivery applications. This review (with 166 references) spotlights the cellular imaging applications of three types of HAp NPs. Specific sections cover aspects of molecular imaging and the various imaging modes, a comparison of the common types of nanoprobes for bioimaging, synthetic methods for making the various kinds of HAp NPs, followed by overviews on fluorescent NPs for bioimaging (such as quantum dots, gold nanoclusters, lanthanide-doped or fluorophore-doped NPs), magnetic HAp NPs for use in magnetic resonance imaging (MRI), luminomagnetic HAp NPs for bimodal imaging, and sections on drug delivery as well as cellular imaging applications of HAp based nanoprobes (including targeted imaging).

Hydrothermal treatment with VO2(B) nanobelts for synthesis of VO2(A) and W doped VO2(M) nanobelts

In this paper, the conversion of VO2(B) nanobelts under the hydrothermal condition in the absence/presence of dopant was studied. The synthetic conditions, such as the reaction temperature, reaction time, quantity of the dopants and kinds of dopants, were briefly discussed to prepare VO2(A) and W doped VO2(M) solid solution. It was found that the dopant played a crucial role in controlling VO2 polymorph, and the results showed that VO2(A) was obtained in the absence of dopant, whereas W doped VO2(M) was obtained in the presence of tungstenic acid. The transformation mechanism from VO2(B) to VO2(A) and W doped VO2(M) was discussed in detail. The phase transition temperature (Tc) of VO2(A) and W doped VO2(M) was evaluated by differential scanning calorimetry. It is found that doped atoms can be successfully doped into the crystal lattice of VO2(M) matrix, and the Tc of W doped VO2(M) can be reduced by W doping. The optical switching properties were studied by the variable temperature infrared spectra, and it was found that the as obtained VO2(A) and W doped VO2(M) had outstanding thermochromic characters and optical switching properties.

Noble metal modified TiO2 for photocatalytic air purification

TiO2 was surface modified with silver, gold, palladium and platinum ion clusters to improve its photocatalytic activity. The effect of metal content and kind of dopant used during preparation procedure on the photoactivity were investigated. in toluene removal which was used as a model volatile organic compound. Toluene, at the concentration of about 100 ppm, was irradiated over noble metal modified TiO2 using light-emitting diodes (LEDs) in four subsequent cycles.

The M-band transmission flux of the plastic foil with a coated layer of silicon or germanium

Silicon (Si) and Germanium (Ge) can be used as the dopant in the ablator material for the purpose of reducing preheating in indirect-drive inertial confinement fusion. Their performances in reducing preheating are quite different. A method to evaluate the difference of these two kinds of dopants has been presented in this letter. In the Shenguang-II high power laser facility, the M-band (1.6–4.4 keV) transmission flux of Si-coated plastic (CH) and Ge-coated plastic (CH) has been measured by using the M-band x-ray diode. In the experiment, we find that the Si-coated CH can absorb more M-band x-rays and thus reduce the preheating of the fuel in our experiment condition. By using the radiation hydrodynamic code MULTI-1D, we got the simulation result which was well suited for the experiment. The comparison of their opacities (Te = 60–100 eV and ρ = 0.1–0.5 g/cm3) also shows that the opacity of Si is higher than that of Ge almost in the whole range of 1.6–4.4 keV.

Microstructure and Magnetic Properties of Low-Fired NiCuZn Ferrite with Different Dopants

The NiCuZn ferrite (Ni0.60Cu0.24Zn0.16Fe2O4) has been prepared by a conventional solid-reaction method and sintered at 900°C with different dopants to adapt to the low temperature cofired ceramic (LTCC) technology. Two kinds of dopants, oxide Bi2O3 (BI) and ferroelectric ceramic Bi4Ti3O12 (BIT), are used in different amounts or combinations (2wt%BI, 2wt%BIT, 2wt%BI + 2wt%BIT, 4wt%BI, and 4wt%BIT) to promote the sintering process. Variation of microstructure and density in each sample has been analyzed. Influence of the doping mode on the magnetic properties of the ferrite has been investigated. It can be found that the ferrite doped with BI has an obvious decrease of both MS and HC in contrast with the ferrite doped with same amount of BIT. Appropriate amounts of BIT is helpful to not only increase MS, but also decrease of HC, compared with the ferrite without doping.

Structure and electrical properties of Ca0.28Ba0.72Nb2O6 ceramics with addition of rare earth oxides (CeO2, La2O3)

Ca0.28Ba0.72Nb2O6 (CBN28) ceramics with addition of CeO2 and La2O3, were prepared by the conventional ceramic fabrication technique. XRD results showed that the single tungsten bronze structure of CBN28 was not changed by adding CeO2 or La2O3. SEM results indicated that both CeO2 and La2O3 dopants were effective in inhibiting the grain growth and suppressing the anisotropic growth behavior in tungsten bronze structure. It was also found that both two kinds of dopants had remarkable effects on the dielectric and ferroelectric properties of CBN28 ceramics. Compared with CBN28 ceramics, the dielectric constant around room temperature εr, dielectric loss tanδ, the degree of diffuseness γ and coercive field Ec were all ameliorated when doping proper amount of CeO2 or La2O3. The comprehensive electric performance was obtained in CBN28–0.3wt% CeO2 and CBN28–0.4wt% La2O3 ceramics. Besides, the underlying mechanism for variations of the electrical properties due to different dopants was explained in this work.

The optical—electrical properties of doped β-FeSi2

By using the pseudo-potential plane-wave method of first principles based on the density function theory, the geometrical, electronic structures and optical properties of FeSi1.875M0.125 (M = B, N, Al, P) were calculated and analyzed. The calculated structural parameters depend strongly on the kinds of dopants and sites. The total energy calculations for substitution of dopants at the SiI and the SiII sites revealed that Al and P prefer the SiI sites, whereas B and N prefer the SiII sites. The calculations predict that B- and Al-doped β-FeSi2 show p-type conduction, while N- and P-doped show n-type. Optical property calculations show that N-doping has little influence on the complex dielectric function of β-FeSi2; B-, N-, Al- and P-doping can enhance the electronic transition, refractive index, and reflection effect in the low-energy range, and weaken the reflection effect at the max peak of reflectivity. These results can offer theoretical guidance for the design and application of optoelectronic material β-FeSi2.

Effects of silver ion exchange and subsequent treatments on the UV–VIS spectra of silicate glasses. I. Undoped, CeO2-doped, and (CeO2 + Sb2O3)-codoped photo-thermo-refractive matrix glasses

The effects of the silver ion exchange and of subsequent UV irradiation and/or heat treatment on the optical density spectra of photo-thermo-refractive matrix glass samples both virgin and doped with cerium and/or antimony oxides were investigated. The incorporation of silver by ion exchange for ~15min at 310°C was found to cause, for all glasses except those with CeO2 content around 0.1mol% or more, a shift of the UV limit of strong absorption to the greater wavelengths by ~70–100nm due to the occurrence of Ag+-related absorption. Complicated changes caused by the UV irradiation and/or heat treatment of ion-exchanged samples in the location of their UV limit of strong absorption and in the absorption throughout the 330–550nm region were analyzed and shown to be greatly influenced by (i) the kind of dopant(s), (ii) chances for shifting the redox and other equilibria involving the dopants at temperatures of particular treatment processes, and (iii) NaBr presence in the glass batch composition. The effect of NaBr addition was explained tentatively in terms of formation, after the heat treatment, of AgBr clusters or nanocrystals.

61.5L: Late‐News Paper: Highly Efficient White OLEDs with Single Solution‐Processed Emitting Layer Consisting of Three Kinds of Dopants

AbstractWe achieved a highly efficient white organic light emitting diode with a single emitting layer consisting of three kinds of dopants. The emitting layer was fabricated with a one‐step solution coating process. A maximum power efficiency of 70 lm/W was obtained by applying high photoluminescent quantum yield dopants and improving light‐extraction efficiency.

Direct preparation and formation mechanism of belt-like doped VO2(M) with rectangular cross sections by one-step hydrothermal route and their phase transition and optical switching properties

VO2(M) shows a reversible first-order metal–insulator transition to metallic rutile phase VO2(R) at 68°C. The large-scale and low-cost synthesis of VO2(M) are challenge for materials scientists. In this paper, belt-like W-doped VO2(M) with rectangular cross sections was successfully synthesized using peroxovanadium (V) complexes as the vanadium precursor and ethanol as the reducing agent by a facile one-step hydrothermal approach for the first time. The samples were separately characterized by XRD, EDS, XPS, XRF, SEM, DSC and variable-temperature FTIR. Some parameters, such as the quantity of the dopants, reaction temperature, reaction time, kinds of dopants and volume of ethanol, were briefly discussed to synthesize W-doped VO2(M) solid solution. It is found that doped atoms can be successfully doped into the crystal lattice of VO2 matrix, and the morphologies of the samples are described as highly faceted micro- and nano-belts structures with rectangular cross sections. The formation mechanism of W-doped VO2(M) was discussed in detail. The phase transition temperature of W-doped VO2(M) can be simply tuned by changing the doping concentration of W atom within appropriate limits. The variable-temperature infrared spectra reveal that the doped VO2(M) has outstanding thermochromic characters and optical switching properties.

Self-assembly growth of electrically conductive chitosan nanofibrous scaffold

We report on the synthesis of an electrically conductive chitosan nanofibrous scaffold (NFS) by a “simple template free self-assembly method” from biopolymer chitosan in the presence of inorganic acids as dopants and ammonium persulphate (APS) as an initiator. The morphology of the chitosan nanofibers scaffold (CS-NFS) was examined by field emission scanning electron microscopy (FE-SEM). Physiochemical characterizations of the CSNFS were analyzed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. It is found that the morphology and structure of the CS-NFS strongly depend on the kinds of dopant used. Cyclic voltammogram measurement reveals that CS nanofibers have high electrocatalytic activity compared to chitosan powder. The CS nanofibers are expected to be useful in electrical, optical, and electrochemical devices. Open image in new window

Physical properties of metal-doped zinc oxide films for surface acoustic wave application

Metal-doped ZnO [MZO] thin films show changes of the following properties by a dopant. First, group III element (Al, In, Ga)-doped ZnO thin films have a high conductivity having an n-type semiconductor characteristic. Second, group I element (Li, Na, K)-doped ZnO thin films have high resistivity due to a dopant that accepts a carrier. The metal-doped ZnO (M = Li, Ag) films were prepared by radio frequency magnetron sputtering on glass substrates with the MZO targets. We investigated on the optical and electrical properties of the as-sputtered MZO films as dependences on the doping contents in the targets. All the MZO films had shown a preferred orientation in the [002] direction. As the quantity and the variety of metal dopants were changed, the crystallinity and the transmittance, as well as optical band gap were changed. The electrical resistivity was also changed with changing metal doping amounts and kinds of dopants. An epitaxial Li-doped ZnO film has a high resistivity and very smooth surface; it will have the most optimum conditions which can be used for the piezoelectric devices.

An Investigation of Transient Effects in Poly(3-hexylthiophenes) Based Thin Film Transistors Caused by Oxygen and Water Molecules

In this article, we investigate hysteresis behavior observed in the current-voltage transfer curve of regioregular poly(3-hexylthiophene)(P3HT) based thin film transistors (PTFTs) using bi-directional voltage sweeping. According to the results of our experiments, the hysteresis effects were closely related to oxygen (O2) and water (H2O) molecules residing in the P3HT active layer. As a result, we hypothesized that O2 and H2O in the P3HT could form two kinds of dopants, i.e., stable and transient states. Stable state dopants, which are commonly thought to be of the acceptor-type dopants, could induce holes in the channel region contributing to better on-current. On the contrary, transient state dopants were found to be unable to induce holes, however could enable the formation of polarization agents and create hysteresis. These two types of dopants seem have a common origin, thus they could be converted into each other through the combination of specific processes and applied external bias. From the viewpoint of device operation stability, except on-current level and characteristics including threshold voltage, off-current magnitude and on/off ratio, the impact of hysteresis should garner the attention of those pursuing high performance PTFTs.

Comparative Studies on the Corrosion Protection Effect of Different Ions Selective Polyaniline Coatings

Different kinds of dopants were selected to dope polyaniline by chemical oxidative polymerization in this paper. Major characteristic peaks and microstructure of the doped polyaniline were analyzed by Fourier transform infrared spectra (FTIR) and scanning electron microscope (SEM). Measurement of membrane potential indicated that polyaniline doped with protonic acid such as sulfosalicylic acid (SSA) and hydrochloric acid (HCl) had characteristic of anionic selectivity, and polyaniline doped with cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) had characteristic of cationic selectivity. Doped polyaniline was added to the epoxy resin to obtain different ions selective coatings, such as anionic coating, cationic coating and bipolar coating. Results of electrochemical test in 5% potassium chloride (KCl) solution (at 60 °C) showed that anti-corrosion performance of the bipolar coating is better than that of cationic coating, and performance of the cationic coating is better than that of anionic coating. And the coatings contained HCl-doped polyaniline had better protection performance than those of SSA-doped because of its micro appearance and distribution.

On the exceptional negative Seebeck effect in 3d-doped β-rhombohedral boron

Interstitial doping with 3d-elements impact the electronic properties of β-rhombohedral boron significantly; in some cases high negative Seebeck coefficients occur. The explanation by simple charge transfer is excluded. We attribute these effects to the correlation among the diluted 3d atoms generating a specific system of electronic states in the band gap. The interaction with Ogitsu’s antiferromagnetic Ising model, describing the incomplete occupancy of regular B sites, is probable. Details depend on the kind of dopants, occupied sites, and occupancies. Very low V, Cr, and Ni contents evoke extraordinary high negative Seebeck coefficients at ambient conditions; e.g. VB 190: S = 450 μVK −1 at 270 K, a shift of more than 1000 μVK −1 compared with pure boron. Structural and electronic properties of B:V, B:Fe, B:Cu and some other 3d transition metal solid solutions in β-rhombohedral boron are discussed.

Electrical conduction behaviors of isovalent and acceptor dopants on B site of (La 0.8Ca 0.2)CrO 3− δ perovskites

The electrical conduction behaviors of isovalent and acceptor dopants on B site of (La 0.8Ca 0.2)CrO 3− δ perovskites at high and low oxygen activities were investigated systematically. In this study, the concept of defect chemistry is used to explain the relationship between the concentration of electron hole with the electrical conductivity. The information of charge compensation mechanisms and defect formation may be valuable for a better understanding of the interconnect of (La 0.8Ca 0.2)CrO 3− δ -based ceramics used for solid oxide fuel cells (SOFCs). Since (La 0.8Ca 0.2)CrO 3− δ -based specimens belong to p-type conductors, their conductivities are proportional to the concentration of electron hole. In reducing atmosphere, the oxygen may be lost and ionic compensation may be take place through the formation of oxygen vacancies and the electrical compensation may arise by changing the valence of Cr from tri-valence to tetra-valence in reducing atmosphere. However the formation of oxygen vacancies has no contribution to electrical conductivity, the compensation mechanism is dominated by the electrical compensation, i.e. the take place a transition of Cr 3+ → Cr 4+ rather than that of ionic compensation, i.e. the formation of oxygen vacancies. Based on the defect chemical reactions and the results of electrical conductivity, the concentration of electron hole at high oxygen activity is larger than that at low oxygen activity. Therefore the electrical conductivity of (La 0.8Ca 0.2)CrO 3− δ -based ceramics at air is larger than that at 5% H 2–95% Ar forming gas. The compensation mechanisms contain ionic and electrical compensation and the ratios of electrical to ionic compensation varied with the kind of dopant which significantly effects the electrical conductivity. The results suggest that the (La 0.8Ca 0.2)Cr 0.9Co 0.1O 3− δ specimen shows high electrical conductivity in air ( σ 850 °C = 59.59 S/cm) and 5% H 2–95% Ar forming gas ( σ 850 °C = 47.98 S/cm) leading it a promising candidate as an interconnect material for SOFCs applications.

Introducing dopants by diffusion to improve the conductivity of silicon quantum dot materials in 3rd generation photovoltaic devices

AbstractAn alternative method to introduce dopants in Silicon rich oxide (SRO) layers was investigated. A silicon dioxide (SiO2) layer containing phosphorous pentoxide (P2O5) or boron (B) was deposited on the quartz substrate. A bilayer structure was subsequently deposited using Si and SiO2. SRO layers were doped via diffusion during the high temperature annealing required to form the Silicon quantum dot (Si‐QD) materials. Two kinds of dopants (phosphorus and boron) were introduced as they are typical dopants for n‐type and p‐type Si respectively. The annealing time was also varied to achieve an optimum conductivity of the quantum dot material. Different Si concentrations in the SRO layers were investigated. A 5% change of Si concentration could change the conductivity of the Si‐QD material by more than one order of magnitude. Using circular transmission line measurement (TLM), the sheet resistivity of the Si‐QD material was extracted. It was demonstrated that this new method of introducing dopants by diffusion is successful. Moreover, it was found that the conductivity of Si‐QD materials decreased with increasing Si concentration in the SRO layers and was also influenced by the type of dopants. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Development of Doped ${\rm MgB}_{2}$ Wires and Tapes for Practical Applications

A review of current developments in the study of chemical doping effect on the superconducting properties of MgB2 wires and tapes is presented, based on the known literature data and our own results. The critical current density of MgB2 can be improved through various kinds of dopants. Among these dopants, doping with carbon-containing materials seems to be the most effective way to improve the Jc performance. The doping effect of carbon in different forms and carbon-based compounds such as SiC, nano-C, metal carbides, as well as aromatic hydrocarbon and carbohydrate on the Jc-B characteristics of MgB2 was discussed in detail. The C can be incorporated into the MgB2 crystal lattice by replacing boron, and thus Bc2 is significantly enhanced due to selective tuning of impurity scattering of two bands in the two-band MgB2. Besides the efforts of increasing Bc2 by carbon doping, the fine grain size and nano-size inclusions caused by doping would create many flux pinning centres improving the Jc-B property of MgB2. Based on these considerations, we suggested some principles for the selection of dopants.

A Novel Strategy for the Synthesis of Sheet‐Like Polyaniline

Polyaniline (PANI) micro/nanosheets are successfully synthesized by a template-free method without using any conventional oxidants. Scanning electron microscopy, transmission electron microscopy, and FT-IR spectroscopy are applied to characterize the products. By investigating the morphologies and chemical structures of the PANI micro/nanosheets, a possible formation mechanism is proposed. In addition, the influences of experimental parameters, such as the kind of dopant, concentration of aniline, and acidity of reaction system, on the morphologies of the PANI micro/nanosheets have been systematically investigated.

Thermoelectric properties of La(1-x)MxCoO3(M=Sr, Ca;x=0, 0.1) ceramics for thermal sensors

We have investigated the effects of dopant on the thermoelectric properties that <TEX>$La_{(1-x)}M_xCoO_3$</TEX>(M=Sr, Ca;x=0, 0.1) bulk ceramics fabricated by the conventional solid state reaction method. The Seebeck coefficient of <TEX>$La_{(1-x)}M_xCoO_3$</TEX>(M=Sr, Ca;x=0, 0.1) bulk ceramics was measured at wide temperature range from 300 K to 673 K. The thermoelectric properties(Seebeck coefficient and electrical resistivity) depend strongly on the kinds of dopants. Sr and Ca dopant decrease the Seebeck coefficient. Density of sintered <TEX>$La_{0.9}Sr_{0.1}CoO_3$</TEX> ceramic at 1523 K was 7.12 <TEX>$g/cm^2$</TEX> and Seebeck coefficient was 35 <TEX>${\mu}V/K$</TEX> at 663 K. However, the electrical resistivity of the Sr doped sample was low and stable.