Surface Photovoltage Properties Research Articles

Syntheses, structures and photoelectronic properties of a series of tri- and tetra-nuclear metal complexes based on a 36-membered tetraphenol macrocyclic ligand

In this article, tetranuclear Zn II coordination complexes [Zn 4L(μ 2-OH) 2]·2(NO 3)·6(CH 3OH)·H 2O ( 1) and [Zn 4L(μ 2-OH) 2(H 2O) 2]·( p-bdc)·2(CH 3OH)·3H 2O ( 2), dinuclear Zn II complex [Zn 4L(NH 2-bdc) 2]·2(CH 3OH)·3H 2O ( 3), and trinuclear Cd II complexes [Cd 3L( m-bdc)]·6.5H 2O ( 4) and [Cd 3L(NH 2-bdc)]·5.5H 2O ( 5), based on a tetraphenol 36-membered macrocycle (L) having four ethylenediamine and four 2,6-diformyl-4-methylphenol functionalities, have been synthesized at room temperature ( p-bdc = 1,4-benzenedicarboxylate, NH 2-bdc = 5-aminoisophthalate and m-bdc = 1,3-benzenedicarboxylate). In 1 and 2, four Zn II centers are bridged by phenoxide and hydroxy atoms of the L ligands to form tetranuclear Zn II complexes. The inorganic and organic anions in 1 and 2 do not coordinate to Zn II centers, but act as counter anions. In 3, two Zn II centers are bridged by two phenoxide O atoms to form a Zn II cluster (Zn 2O 2N 4). Moreover, two (Zn 2O 2N 4) clusters within the ring of the L ligand are further bridged by two NH 2-bdc anions in a monodentate fashion. Compound 4 possesses the trinuclear Cd II clusters (Cd 3N 8O 8), which has a similar structure to compound 5. The trinuclear Cd II clusters are bridged by the dicarboxylate anions to yield an infinite coordination polymers chain. The photoelectric transfer properties of complexes 1, 2 and 4 were investigated by surface photovoltage spectroscopy (SPS) and the field-induced surface photovoltage spectra (FISPS) techniques. The results reveal that the complexes exhibit positive surface photovoltage (SPV) responses in the range of 300–600 nm, possessing the p-type semiconductor characteristics. So far, the surface photovoltage properties of the macrocycle complexes based on tetraphenol macrocyclic ligands were investigated for the first time. Moreover, elemental analyses, IR spectra, and luminescent properties of these compounds were also studied.

A comparative study on plate-like and flower-like ZnO nanocrystals surface photovoltage property and photocatalytic activity

ZnO nanostructures materials with two-dimensional (2D) plate-like and three-dimensional (3D) flower-like morphologies have been synthesized via facile hydrothermal process. Scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD) have been used to characterize the samples. We have compared the surface photoelectric properties of flower-like ZnO with that of plate-like ZnO by means of surface photovoltage (SPV), field-induced surface photovoltage (FISPV), transient photovoltage (TPV) and surface photocurrent (SPC) techniques. Based on the photovoltage responses, the influence of the morphology on transfer characteristics of photogenerated charge carriers was discussed. The synthesized flower-like ZnO exhibited more efficient separation and transfer properties of photogenerated charge carriers than that of plate-like ZnO in the UV region due to the special flower-like hierarchical nanostructures. We have also evaluated the photocatalytic activity of the ZnO samples by photodegradation efficiency of RhB. The experiments demonstrated that RhB in aqueous solution was more efficiently photodegraded using flower-like ZnO than plate-like ZnO. The results also show the consistency between the carrier dynamics of photogenerated electron–hole pairs and photocatalytic activity.

In0.49Ga0.51P/GaAs 이종접합 구조의 표면 광전압 특성

Metal-organic chemical vapour deposition (MOCVD) 법으로 성장된 <TEX>$In_{0.49}Ga_{0.51}P$</TEX>/GaAs 이종접합 구조의 특성을 표면 광전압(surface photovoltage; SPV) 분광법으로 조사하였다. SPV 측정은 입사광의 세기, 변조 주파수, 온도의 함수로 수행하였다. 상온에서 시료의 띠간격 에너지(band gap energy)는 GaAs와 <TEX>$In_{0.49}Ga_{0.51}P$</TEX>는 각각 1.400 및 1.893 eV이었다. 광세기를 증가시킴에 따라 SPV 크기는 증가하는 반면에, 변조 주파수를 증가시킴에 따라 SPV 크기는 감소하였다. 그리고 SPV 스펙트럼의 온도 의존성으로부터 GaAs와 <TEX>$In_{0.49}Ga_{0.51}P$</TEX>의 띠간격 에너지의 변화를 Varshni 및 Bose-Einstein 표현에 의해 분석하였다. We report the surface photovoltage (SPV) properties of <TEX>$In_{0.49}Ga_{0.51}P$</TEX>/GaAs heterostructure grown by metal-organic chemical vapour deposition (MOCVD). The SPV measurements were studied as a function of modulation beam intensity, modulation frequency and temperature. From a line shape analysis of room temperature derivative surface photovoltage (DSPV) spectrum, the band gap energies for GaAs and <TEX>$In_{0.49}Ga_{0.51}P$</TEX> transitions were 1.400 and 1.893 eV respectively. The surface photovoltage (SPV) increases with increasing the light intensity and temperature, whereas the SPV decreases with increasing the modulation frequency. From the temperature variation of the energy gaps, we have analysis by both Varshni and Bose-Einstein type expressions.

Surface photovoltage properties and photocatalytic activities of nanocrystalline CoFe2O4 particles with porous superstructure fabricated by a modified chemical coprecipitation method

In this study, nanocrystalline CoFe2O4 particles with porous timber-like superstructure were synthesized by a modified chemical co-precipitation route with calcination temperatures of 573, 673, 773, 873, and 973 K, respectively. The structural properties of the samples were systematically investigated by X-ray powder diffraction, scanning electronic microscopy, energy-dispersive X-ray spectra, UV–Vis diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage (SPV) measurement. The photocatalytic performances of the CoFe2O4 samples were comparatively studied by the degradation of 4-chlorophenol under Xe lamp irradiation. The results indicated that the sample calcined at 673 K exhibited the highest photocatalytic efficiency among the five samples.

From 2-D CuO nanosheets to 3-D hollow nanospheres: interface-assisted synthesis, surface photovoltage properties and photocatalytic activity

CuO hierarchical hollow nanostructures, assembled by nanosheets, were successfully prepared in n-octanol/aqueous liquid system through a microwave approach. Controlled experiments revealed that both bubble and interface play key roles in determining the self-assembly process of CuO hierarchical hollow nanostructures, and the morphology/size of building blocks and final products could be readily tuned by adjusting reaction parameters. Furthermore, a self-assembly mechanism of aggregation-then-growth process through bubble template was proposed for the formation of the hollow hierarchical architectures. Photocatalytic performance evidenced that the obtained CuO hierarchical hollow nanostructures possessed superior photocatalytic efficiency on RhB than that of non-hollow nanostructures, which could be easily demonstrated by SPS response about the separation and recombination situation of photogenerated charges.

TiO 2 nanowires sensitized with CdS quantum dots and the surface photovoltage properties

TiO 2 nanowires prepared by thermal annealing of anodized Ti foil were sensitized with CdS quantum dots (QDs) via chemical bath deposition (CBD). Microstructural characterizations by SEM, TEM and XRD show that the CdS nanocrystals with the cubic structure have intimate contact to the TiO 2 nanowires. The amount of CdS QDs can be controlled by varying the CBD cycles. The experiment results demonstrate that the surface photovoltage (SPV) response intensity was significantly enhanced and the surface photovoltage response region was also expanded obviously for the TiO 2 NWs sensitized by CdS QDs.

Silicon dioxide coating of CeO 2 nanoparticles by solid state reaction at room temperature

The synthesis of SiO 2 coated CeO 2 nanoparticles by humid solid state reaction at room temperature is described. Transmission electron microscope results show that CeO 2 particles were coated with a layer of SiO 2. Binding energy of Ce 3d 5/2 was shifted from 883.8 to 882.8 eV after coating in the XPS Ce 3d spectra. This confirms the chemical bond formation between SiO 3 2− and Ce 4+. Because the surface photovoltage property of CeO 2 nanoparticles that were used as core materials in the experiment approaches to that of CeO 2 macroparticles, peak P2 (electron transition from O 2p on surface to Ce 4f) disappeared in the surface photovoltage spectrum of CeO 2 nanoparticles. Also, the effect of SiO 2 on the electron transition from O 2p to Ce 4f results in the lowering of surface photovoltage response intensity of P1 peak (electron transition from O 2p in bulk to Ce 4f).

Photoelectric properties of material of N, N′-bis(4′-aminophenyl)-1,4-quinonenediimine doped with heteropolyacid

In this paper, we have synthesized aniline oligomer composite material using heteropolyacid (H 4SiW 12O 40) as dopant. The UV–Vis absorption spectra, the photoluminescence and surface photovoltage properties of the composite materials were studied. The band at 572 nm is weakened and even disappeared and the bands at 268, 412 and 771 nm appeared after the aniline oligomer was doped. For the first time, we found the photoluminescence property of aniline oligomer. In a certain range, the doping is favorable for an increase of intensity of the fluorescence emission band at 860 nm, although the corresponding characteristic absorption band at 572 nm is weakened in the composite material. Surface photovoltage spectra shows that surface potential of the composite material decreased with the increase of the doping concentration, which explained reasonably the photoluminescence property. In the composite material, the photo-response range is widened due to the choice of photoactive heteropolyacid (H 4SiW 12O 40).

Surface photovoltaic characterizations of porous silicon layers

The surface photovoltage properties of porous silicon layers were investigated as a function of anodization using surface photovoltage spectroscopy (SPS), combined with photoluminescence spectroscopy (PL). Fourier transform IR spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the chemical composition, microscopic structure and photovoltaic behavior of the porous silicon layers depend strongly on the anodizing conditions. It is suggested that the chemical composition and microscopic structure model the electronic and optical properties of porous silicon. The SPS and PL experiments indicate directly the excitation and emission processes of porous silicon layers. Marked differences were observed in the SPS and PL spectra of porous silicon layers with a variety of chemical compositions and microscopic structures. These experimental observations provide a clear signature of the correlation of excitation and emission in porous silicon.