IR Luminescence of Polyfunctional Associates of Indocyanine Green and Ag2S Quantum Dots

Optics and Spectroscopy - In this work, manifestations of IR luminescence sensitization of Indocyanine Green during conjugation with colloidal Ag2S quantum dots with an average size of 2.2 and 3.7...     

Transient Absorption Dynamics and Nonlinear Optical Response in Colloidal Ag2S Quantum Dots

Optics and Spectroscopy - The mechanism of the nonlinear optical response of colloidal solutions of Ag2S quantum dots passivated with thioglycolic acid molecules is considered. Appearance of...     

Luminescent Properties of Colloidal Ag2S Quantum Dots for Photocatalytic Applications

Physics of the Solid State - The structural and optical properties of colloidal Ag2S quantum dots in different environments are studied. With the help of transmission electron microscopy, X-ray...     

Interface in Ag2S/ZnS Nanoheterostructures

JETP Letters - The structure of Ag2S/ZnS nanoheterostructures has been analyzed taking into account the morphology and elastic properties of Ag2S and ZnS sulfide single crystal particles. The...     

Atomic Displacements in the α–β Phase Transition in Ag 2 S and in Ag 2 S/Ag Heterostructure

Orientation relationships between low-temperature monoclinic semiconductor α-Ag2S acanthite and high-temperature body-centered β-Ag2S argentite are determined. It is shown that, in cubic argentite, possible distances between silver atoms are too small for the sites of the metal sublattice to be occupied by Ag atoms with probability equal to one. With regard to the possible arrangement of Ag atoms, it is shown that, during the “acanthite–argentite” transformation, the jump of a silver ion from site (e) of monoclinic acanthite to site (j) of cubic argentite is the most probable process. It is established that the acanthite–argentite transformation in Ag2S/Ag heteronanostructure is accompanied by the formation of a conductive channel of silver Ag and β-Ag2S argentite under the application of an external voltage. The on-to-off-state current ratio in the synthesized Ag2S/Ag heteronanostructure is approximately equal to 670. For the Ag2S/Ag heteronanostructure, the energy barrier for the hopping of an Ag+ ion from an atomic site of monoclinic acanthite to a site of cubic argentite is estimated.     

The C-V characteristics of TiO2/p-Si/Ag,GNR doped TiO2/p-Si/Ag and MWCNT doped TiO2/p-Si/Ag heterojunction devices

The TiO₂/p-Si/Ag, graphene (GNR) doped TiO₂/p-Si/Ag and multi-walled carbon nanotube (MWCNT) doped TiO₂/p-Si/Ag heterojunction devices were fabricated by electrospinning technique at same conditions. Their structural, morphological properties, thermal analyses (TGA), and capacitance voltage characteristics were studied and compared. The undoped, GNR and MWCNT doped TiO₂ structures obtained successfully according to XRD measurements. Morphological properties of the undoped, GNR and MWCNT doped TiO₂ composite structures have rod or ribbon like structures. The TGA result confirmed the GNR and MWCNT doped TiO₂ structures. The C-V and G-V measurements were employed for electrical characterization of the TiO₂/p-Si/Ag, GNR doped TiO₂/p-Si/Ag and MWCNT doped TiO₂/p-Si/Ag devices for various frequencies at room temperatures. The results imparted that the capacitance and conductance behaviors of all devices are strong functions of the frequency and voltage. The electrical parameters were calculated from C⁻²-V plots of the heterojunction devices and compared for three devices. The transient photocapacitance plots revealed that the devices can be employed for optical communication applications.     

Microstructure of Ag2S–As2S3 glasses

Field effect-scanning electron microscopy (FE-SEM) and electric force microscopy (EFM) measurements were carried out on bulk Ag₂S–As₂S₃ glasses with silver concentrations 1.2, 4 and 9.8 at.%. While the first glass was found to be homogeneous, the presence of chemical contrasts and electrical heterogeneousness throughout the other two samples indicated that the glasses were phase separated. Moreover, it appeared that, while silver-rich nodules of 200–350 nm were embedded in a silver-poor connecting phase in the glass containing 4 at.% Ag, it was the opposite that occurred in the glass containing 9.8 at.% Ag. Such an inversion explained the large difference of 4–5 orders of magnitude in the conductivity of the two glasses.     

Charge‐transfer contributions in surface‐enhanced Raman scattering from Ag,Ag2S and Ag2Se substrates

The degree of charge‐transfer in Ag–4‐mercaptopyridine (Mpy) and Ag₂S–4‐Mpy systems is investigated by use of surface‐enhanced Raman spectroscopy (SERS). Ag₂S and Ag₂Se nanoparticles are prepared on the basis of the former formation of Ag nanoparticles to make the SERS analytical objects comparable. We utilize the intensity of the non‐totally symmetric modes (either b₁ or b₂) as compared with the totally symmetric a₁ modes to measure the degree of charge‐transfer. We find ~25% of charge‐transfer contribution for Ag–4‐Mpy, whereas 81 ~ 93% for Ag₂S–4‐Mpy. It means that the charge‐transfer resonance contribution dominates the overall enhancement in SERS of Ag₂S–4‐Mpy. Energy level diagram is applied to discuss the likely charge‐transfer transition between Ag, Ag₂S, Ag₂Se and 4‐Mpy. This article may point out the link among the three main resonance sources and could enable some insights into the electronic pathways available to the metal‐molecule and semiconductor‐molecule systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Optical Properties of Zinc Sulfide Nanopowders and ZnS/Ag2S Heteronanostructures

Physics of the Solid State - Nanopowders of zinc sulfide (ZnS) and ZnS/Ag2S heteronanostructures were synthesized by chemical deposition from aqueous solutions. A change in the ratio between the...     

Preparation and properties of nano-sized Ag and Ag2S particles in biopolymer matrix

Silver (Ag) and silver sulfide (Ag₂S) nanoparticles were synthesized in a sago starch matrix. The resulting nanocomposites were investigated using structural, optical and thermal methods. XRD spectra of the nanocomposites confirmed the presence of nanostructured silver (cubic phase) and silver sulfide (monoclinic phase) in the matrix. TEM micrographs showed that the nanoparticles are mostly spherical in shape. Analyzes of the optical properties of the silver nanocomposite aqueous dispersions/solutions of various concentrations were carried out. The results and the theoretical considerations suggested that at high concentrations there is a release of silver nanoparticles from the composite in the water environment. Further dilution produces homogeneous solution in which silver nanoparticles are capped with starch macromolecules. TGA analysis revealed reduced thermal stability of the nanocomposites with respect to pure starch matrix.     

Ag<Subscript>2</Subscript>S/Ag heteronanostructure

An Ag₂S/Ag heteronanostructure has been prepared for the first time by hydrochemical deposition. The “acanthite α-Ag₂S–argentite β-Ag₂S” phase transformation has been studied in situ by high-temperature X-ray diffraction and transmission electron microscopy. The crystal structure of argentite has been revealed. It has been found that the concentration of vacant sites in the metal sublattice of argentite exceeds 92%. The reversible acanthite–argentite transformation in the Ag₂S/Ag heteronanostructure at the application of the external bias voltage is considered.     

Resonant Nonradiative Energy Transfer in Hybrid Associates of Thionine Molecules and Ag2S Colloidal Quantum Dots with Different Luminescence Mechanisms

Optics and Spectroscopy - We have considered the resonant nonradiative energy transfer in hybrid associates of thionine dye (TH+) molecules and Ag2S colloidal quantum dots (QDs) passivated with...     

聚氨酯/硫化银纳米复合材料的合成及荧光传感性能

通过生物矿化合成了聚氨酯/Ag2S纳米复合薄膜．通过傅里叶变换红外光谱研究、扫描量热法(DSC)、扫描电镜等方法研究了硫化银纳米粒子对复合薄膜物理性质的影响．用DSC 测定了复合材料的热 稳定性．通过对纳米复合材料荧光性能的研究发现薄膜对Ni(II)的存在非常敏感,少量Ni(II)离子的存在使得荧光光谱强度迅速增加．可以预测此复合薄膜可被开发成水溶液中Ni(II)的传感器．     

Optical Properties of Plasmon Resonances with Ag/SiO2/Ag Multi-Layer Composite Nanoparticles

Optical properties of plasmon resonance with Ag/SiO2/Ag multi-layer nanoparticles are studied by numerical simulation based on Green＇s function theory. The results show that compared with single-layer Ag nanoparticles, the multi-layer nanoparticles exhibit several distinctive optical properties, e.g. with increasing the numbers of the multi-layer nanoparticles, the scattering efficiency red shiRs, and the intensity of scattering enhances accordingly. It is interesting to find out that slicing an Ag-layer into multi-layers leads to stronger scattering intensity and more ＂hot spots＂ or regions of stronger field enhancement. This property of plasmon resonance of surface Raman scattering has greatly broadened the application scope of Raman spectroscopy. The study of metal surface plasmon resonance characteristics is critical to the further understanding of surface enhanced Raman scattering as well as its applications.     

Elastic Properties of Ag2S and ZnS Nanocrystalline Cubic Sulfides

Physics of the Solid State - The structure of Ag2S/ZnS heteronanostructures is considered taking into account the anisotropy of elastic properties of Ag2S and ZnS sulfides. We showed that a large...     

Quantum Monte Carlo investigation of the 2D Heisenberg model with S=1/2

The two-dimensional (2D) Heisenberg model with anisotropic exchange (Δ = 1−J _x /J _z ) and S=1/2 is investigated by the quantum Monte Carlo method. The energy, susceptibility, specific heat, spin-spin correlation functions, and correlation radius are calculated. The sublattice magnetization (σ) and the Néel temperature of the anisotropic antiferromagnet are logarithmic functions of the exchange anisotropy: 1/σ+1+0.13(1)ln(1/Δ). Crossover of the static magnetic structural factor as a function of temperature from power-law to exponential occurs for T _c /J≈0.4. The correlation radius can be approximated by 1/ξ=2.05T ^1.0(6)/exp(1.0(4)/T). For La₂CuO₄ the sublattice magnetization is calculated as σ=0.45, the exchange is J=(1125–1305) K; for Er₂CuO₄ J∼625 K and the exchange anisotropy Δ∼0.003. The temperature dependence of the static structural magnetic factor and the correlation radius above the Néel temperature in these compounds can be explained by the formation of topological excitations (spinons). Fiz. Tverd. Tela (St. Petersburg) 41, 116–121 (January 1999)     

Layer-by-layer assembly of Ag2S quantum dots-sensitized ZnO/SnO2 core-shell nanowire arrays for enhanced photocatalytic activity

Ag₂S quantum dots-sensitized ZnO/SnO₂ core-shell nanowire arrays were successfully synthesized layer by layer through hydrothermal growth, atomic layer deposition, and successive ionic layer adsorption and reaction process. By introducing the two-layer semiconductors, the bandgap of ZnO component in the arrays was slightly modulated, while the light absorption was obviously improved with an absorptivity higher than 95% in visible and ultraviolet range. In contrast to the ZnO NW arrays, the photocurrent response of the ZnO/SnO₂/Ag₂S NW arrays for the visible light was improved from 0.42 μA to 22.5 μA, and the photodegradation efficiency of methylene blue was increased from 45.24% to 71.61%, and 42.61% to 57.58%, respectively in visible light and ultraviolet light. Band structure analysis indicated that the coating layer brought different staggered gaps and suitable band alignment for efficient photocatalytic performance, which could be extended to design heterogeneous semiconductor nanomaterials for their potential applications.     

Preparation and photoelectrochemical performance of Ag/graphene/TiO2 composite film

By dipping-lifting in sol-gel solution and reducing process, the graphene/TiO₂ composite film on the glass plate was first prepared. Then, the Ag/graphene/TiO₂ composite film was fabricated by interface reaction with AgNO₃ and N₂H₄·H₂O on the surface of graphene/TiO₂ composite film. The characterization results show that the uniform porous TiO₂ film is made up of the anatase crystal, and the Ag/graphene/TiO₂ composite film is constructed by doping or depositing graphene sheets and Ag nanoparticles on the surface of TiO₂ film. The photoelectrochemical measurement results indicate that the Ag/graphene/TiO₂ composite film has an excellent photoelectrochemical conversion property.