Photoinduced electron transfer mechanism between green fluorescent protein molecules and metal oxide nanoparticles

Green fluorescent protein (GFP) molecules are attached to titanium dioxide and cadmium oxide nanoparticles via sol–gel method and fluorescence dynamics of such a protein–metal oxide assembly is investigated with a conventional time correlated single photon counting technique. As compared to free fluorescent protein molecules, time-resolved experiments show that the fluorescence lifetime of GFP molecules bound to these metal oxide nanoparticles gets shortened dramatically. Such a decrease in the lifetime is measured to be 22 and 43 percent for cadmium oxide and titanium dioxide respectively, which is due to photoinduced electron transfer mechanism caused by the interaction of GFP molecules (donor) and metal oxide nanoparticles (acceptor). Our results yield electron transfer rates of 3.139×10⁸ s⁻¹ and 1.182×10⁸ s⁻¹ from the GFP molecules to titanium dioxide and cadmium oxide nanoparticles, respectively. The electron transfer rates show a marked decrease with increasing driving force energy. This effect represents a clear example of the Marcus inverted region electron transfer process.     

Nanonecklace of CdO through simple solution chemistry

CdO nanonecklace like structure with interconnected nanobeads were produced by air annealed Cd(OH)₂ nanowire structure thin film at 290 °C. Simple and low cost chemical route has been successfully employed for the synthesis of Cd(OH)₂ nanowires on fluorine doped tin oxide (FTO) coated glass substrates at room temperature (27 °C). Structural analysis confirmed the conversion of hydroxide phase to the oxide phase by annealing which also leads to change in optical band gap from 3.5 to 2.34 eV. The necklace like nanostructure represent unique surface morphology which can be emerged as a potential candidate towards wide range of applications in different fields of nanotechnology such as solar cell, gas sensor, supercapacitor and photo-catalyst.     

Development of transparent conducting copper and iron co-doped cadmium oxide films: Effect of annealing in hydrogen atmosphere

Hydrogenated (annealed in hydrogen atmosphere) cadmium oxide (CdO) thin films co-doped with iron (Fe) of different levels and fixed (2.5%) copper (Cu) amount were deposited on glass and silicon wafer substrates by thermal evaporation. The films were characterised with X-ray fluorescence, X-ray diffraction, optical spectroscopy, and dc-electrical measurements. The obtained results show important improvements in the conductivity, mobility, and carrier concentration compared to un-doped and non-hydrogenated CdO. Hydrogenated CdO doped with 2.5% Cu and 1.3% Fe improved the conductivity (2293.6 S/cm) by ~46 times, mobility (78.31 cm²/V s) by ~11 times, and carrier concentration (1.82×10²⁰ cm⁻³) by ~4 times. This suggests the possibility of using CdO:Cu:Fe–H as transparent-conducting-oxide and dilute-magnetic-semiconductor field of applications.     

Improving carriers mobility in copper and iron-codoped CdO

Thin films of Fe and Cu-codoped CdO (CdO:Cu:Fe) with different Fe content and fixed Cu content were deposited in a high vacuum on glass and Si wafer substrates. These films were studied by X-ray fluorescence (XRF), X-ray diffraction (XED), optical spectroscopy, and dc-electrical measurements. The structural results show enhancement of film [1 1 1] orientation with Fe doping especially with 1.3%Fe film. Also, light doping with Fe improves the dc-conduction parameters of the CdO:Cu:Fe films so that the utmost enhancement of mobility (90.5 cm²/Vs) and conductivity (1470.6 S/cm) was found with 1.3 wt% Fe doping level. It was found that the variation in the bandgap is related to the variation in electron concentration that caused by Fe doping. For low Fe ion concentration (<1.3 wt% ), the bandgap varies according to the Moss–Burstein model.     

Sodium dodecyl sulfate-assisted SILAR synthesis of nanostructured cadmium oxide films

Nanostructured CdO films were prepared on glass substrates by a surfactant – sodium dodecyl sulfate (SDS) – assisted SILAR technique. The influence of SDS concentrations of the growth solution on the structural, morphological and optical properties of the films was investigated and discussed. From the metallurgical microscope and scanning electron microscope images, it was seen that the surface morphology of the films are significantly enhanced by SDS addition. XRD investigations confirmed that the films have good crystallinity levels and are grown preferentially in (111) and (200) orientations. UV–vis. spectroscopy investigations showed that the bandgap and transmittance values of the films are affected dramatically by SDS concentrations.     

Ultrasonic synthesis of Zn-doped CdO nanostructures and their optoelectronic properties

The effect of Zn dopant on the growth of cadmium oxide (CdO) nanostructures through a sonochemical method was investigated. The X-ray diffraction (XRD) patterns of the nanoparticles show CdO cubic structures for the produced samples. Field emission scanning electron microscope (FESEM) images reveal that morphologies of the samples change, when they are doped with Zn atoms, and their sizes reduce. Room temperature photoluminescence (PL) and UV-Vis spectrometers were used to study optical properties of the samples. Evaluation of optical properties indicates that different emission bands result from different transitions and the value of CdO energy band gap increases due to doping. Studies of electrical properties of the nanostructures demonstrate that Zn dopant enhances electrical conductivity and photocurrent generation as the result of light illumination on the nanostructures due to improved density of photo-generated carriers. Considering the obtained outcomes, Zn dopant can alter the physical property of the CdO nanostructures.     

Effect of tellurium doping on the structural, optical, and electrical properties of CdO

Te-doped CdO thin-films (1%, 3%, and 5%) have been prepared by a vacuum evaporation method on glass and silicon-wafer substrates. The prepared films were characterised by X-ray fluorescence, X-ray diffraction, UV-VIS-NIR absorption spectroscopy, and dc-electrical measurements. Experimental data indicate that Te ions doping slightly stresses the host CdO crystalline structure and changes the optical and electrical properties. The bandgap of the host CdO was suddenly narrowed by about 23% due to a little (1%) doping with Te ions. This bandgap shrinkage was explained by effects of trap levels overlapping with conduction band. The electrical behaviours of the Te-doped CdO films show that they are degenerate semiconductors with a bandgap of 1.7-2.2 eV. The 1% Te-doped CdO film shows increase its mobility by about 5 times, conductivity by ∼140 times, and carrier concentration by ∼27 times, relative to undoped CdO film. From transparent-conducting-oxide point of view, Te is sufficiently effective for CdO doping. Finally, the absorption in the NIR spectral region was studied in the framework of the classical Drude theory.     

Effect of heat treatment on physical properties of CdO films deposited by sol–gel method

CdO film has been deposited by sol–gel spin coating method on the glass substrate and then the film has been annealed at 400, 500, 600 °C for 1 h. Effect of annealing temperature on the structural and optical properties of the film has been investigated. The crystal structure and orientation of the as-grown and annealed CdO films have been investigated by X-ray diffraction method. Annealed CdO films are polycrystalline with (111) preferential orientation. The information on strain and grain size is obtained from the full width-at-half-maximum (FWHM) of the diffraction peaks. Texture coefficient and lattice constant have been calculated. The surface morphology of the films has been analyzed. The optical band gap value decreased with increasing the annealing temperatures.     

Non-aqueous electrodeposition of ZnO and CdO films

ZnO films were electrodeposited from a dimethylsulfoxide bath containing dissolved gaseous oxygen. Variations in deposition parameters and their effects on the structural (crystal size, growth direction), optical (bandgap variations, photoluminescence) and electrical (conductivity) properties are described. The technique was extended to give highly-conducting films of CdO.     

蒸发氧化法制备高品质活性氧化镉粉末

开发了高品质活性氧化镉粉末的制备工艺，系统地探索了工艺条件对氧化镉电池材料电化性能的影响。对样品进行了物化性能及电性能检测，结果表明，采用蒸发氧化法可制备出镍镉充电电池用高品质活性氧化镉粉末。