Viruntachar Kruefu

Flame-made niobium doped zinc oxide nanoparticles in bulk heterojunction solar cells

We report fabrication and measurement of bulk heterojunction solar cells utilizing a poly(3-hexylthiophene) (P3HT), phenyl-C61-butyric acid methyl ester (PCBM) composite loaded with different concentrations of niobium doped zinc oxide (Nb/ZnO) nanoparticles produced by flame spray pyrolysis. Nanoparticles with different niobium concentrations were compared, along with devices without Nb/ZnO nanoparticles and with undoped ZnO nanoparticles. It was found that niobium doping leads to a slight increase in open circuit voltage and an increase in short circuit current that scales with niobium concentration. Additional comparison was made between the nanoparticles with 3% niobium by weight to unloaded devices. These also showed a similar open circuit voltage increase and an increase in current that scales with Nb/ZnO nanoparticle concentration to 30% by volume and drops off at 33% Nb/ZnO by volume. Possible mechanisms for these improvements are discussed.

Effects of niobium-loading on sulfur dioxide gas-sensing characteristics of hydrothermally prepared tungsten oxide thick film

Nb-loaded hexagonal WO3 nanorods with 0-1.0 wt% loading levels were successfully synthesized by a simple hydrothermal and impregnation process and characterized for SO2 sensing. Nb-loaded WO3 sensing films were produced by spin coating on alumina substrate with interdigitated gold electrodes and annealed at 450°C for 3 h in air. Structural characterization by X-ray diffraction, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller analysis showed that spherical, oval, and rodlike Nb nanoparticles with 5-15 nm mean diameter were uniformly dispersed on hexagonal WO3 nanorods with 50-250 nm diameter and 100 nm-5 µm length. It was found that the optimal Nb loading level of 0.5 wt% provides substantial enhancement of SO2 response but the response became deteriorated at lower and higher loading levels. The 0.50 wt% Nb-loaded WO3 nanorod sensing film exhibits the best SO2 sensing performances with a high sensor response of ∼10 and a short response time of ∼6 seconds to 500 ppm of SO2 at a relatively low optimal operating temperature of 250°C. Therefore, Nb loading is an effective mean to improve the SO2 gas-sensing performances of hydrothermally prepared WO3 nanorods.

Single-wall carbon nanotube modified glassy carbon electrode for electroanalytical determination of dopamine

In this research, a glassy carbon electrode modified with single-wall carbon nanotubes for electrochemical determination of dopamine was studied by cyclicvoltammetry (CV) and differential pulse voltammetry (DPV). The oxidation and reduction potentials of dopamine using voltammetric technique were measured. The SWCNTs/GC 10 µL was used to test the linearity of anodic oxidation of dopamine by DPV. The peak current increased linearly with concentration of dopamine in the range of 2.5–25 ppm (R2 =0.9766). For the life time of the SWCNTs/GC, the cut-off criterion of the DPV was detected in the reduction of current by 50 %. The lifetime of the SWCNTs-modified depended on the oxidation of dopamine because of fouling of the electrode surface due to the adsorption of oxidation products. 34 repetition cycles was obtained. The detection limit of the dopamine as obtained from the oxidation current in DPV was 0.021 ppm (S/N=3) with minimum current for the detection of dopamine of 0.033 µA. The reproducibility of electrocatalytical studies was better within 90% (10% RSD). The relative standard deviation (RSD) of 8.42% for 100 ppm dopamine (n=20) showed excellent reproducibility. Drug samples obtained from Radvitee hospital were tested as the mentioned procedure. The percentage recovery of dopamine in drug samples was 120.

Gas-Sensing Properties of Pt-V2O5 Thin Films for Ethanol Detection

In the present work, vanadium pentoxide (V2O5) nanoparticles have been investigated for monitoring ethanol (C2H5OH) at ppm levels in air. A one-step flame spray pyrolysis (FSP) process has been applied for the synthesis of vanadium pentoxide (V2O5) and platinum-loaded vanadium pentoxide (Pt-V2O5) nanoparticles. The samples have been studied to characterize their morphological and microstructural properties by X-ray diffraction and transmission electron microscopy. Pt addition to V2O5 samples were verified by energy dispersive X-ray spectrometry mode. The specific surface area of the nanoparticles was measured by nitrogen adsorption method. The application of the produced nanoparticles as sensitive and selective ethanol resistive sensor has been demonstrated. The Pt-loaded V2O5 sensor has shown higher response towards ethanol at ppm-level concentrations compared to unloaded one.

C2H5OH Gas Sensing Based on Poly(3-hexylthiophene)/Nb-Loaded ZnO Nanocomposite Films

The C2H5OH gas sensors were developed using flame-made 0.75mol%Nb/ZnO NPs composite with P3HT as the sensing materials. The composite films of P3HT: 0.75mol% Nb/ZnO NPs in the ratio of 4:1, 3:1, 2:1, 1:1 and 1:2 were prepared by drop casting method onto Al2O3 substrates interdigitated with Au electrodes. The sensing films were analyzed by XRD, SEM and EDS. The gas sensing of C2H5OH was studied at the room temperatures. It was found that the composite films P3HT:0.75mol% Nb/ZnO NPs in the ratio of 2:1 showed the highest sensitivity and fast response time towards C2H5OH gas at room temperature.

The Effect of Side-Chain Structure on Copolymer-Based Bulk Heterojunction Solar Cells

This paper describes the synthesis and photovoltaic studies of copolymer based on benzo[1,2-b:4,5-b′]dithiophene and 2,1,3-benzothiadiazole. Bulk-heterojunction solar cells were fabricated by using chlorobenzene, and 2% chloronapthalene as a solvent additive in chlorobenzene. The copolymers as the electron donor were blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as the electron acceptor. The effect of side–chain on BDT was compared between 4,8-bis(1-pentylhexyl)benzo[1,2-b: 4,5-b′]dithiophene (C11BDT) and 4,8-bis(1-butylhexyl)benzo[1,2-b:4,5-b′]dithioph ene (C9BDT). The power conversion efficiency (PCE) was improved with the shorter side–chain. The highest PCE was found in PC9BDTBT with 2.29%.

Enhancement of the Efficiency of Polymer Solar Cells by Blending Nb/ZnO Nanoparticles into Poly(3-hexylthiophene):[6,6]-phenyl C61-butyric Acid Methyl Ester

Bulk-heterojunction (BHJ) solar cells utilizing P3HT:PCBM composite loaded with niobium-doped zinc oxide nanoparticles (Nb/ZnO NPs) produced by flame spray pyrolysis were fabricated. The devices loaded with and without Nb/ZnO NPs were compared. It was found that niobium doping led to a slight increase in open circuit voltage and an increase in short-circuit current. The effect of co-solvent (1,3,5-trichlorobenzene; TCB) in chlorobenzene in the polymer solution was also investigated on the morphology and performance of a P3HT:PCBM and P3HT:PCBM:Nb/ZnO bulk-heterojunction solar cells. The device efficiency was improved due to a good quality of the thin film nanostructure and annealing time.

Flame-made Nb-doped zinc oxide nanoparticles for application in polymer solar cells

Flame spray pyrolysis (FSP) is a very promising technique for synthesis of high purity nano-sized materials with controlled size and crystallinity in one step. FSP was employed to synthesize pure ZnO and niobium-doped ZnO (Nb/ZnO) nanoparticles containing 0.1–4 mol% Nb. ZnO is one of the most versatile and most widely applied as catalytic metal oxide. Precursor solutions of zinc naphthenate and niobium (V) ethoxide in toluene/methanol (70/30 vol%) were sprayed and combusted, resulting in crystalline and nanostructured particles. The crystalline phase, morphology and size of the nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The specific surface area of the nanoparticles was measured by nitrogen adsorption (BET analysis). The ZnO nanoparticles were observed as particles having the clear spherical, hexagonal and rod-like morphologies. The crystallite sizes of ZnO spherical and hexagonal particles were in the range of 5–20 nm. ZnO nanorods were found to be ranging from 5–20 nm in width and 20–40 nm in length. The optical properties of ZnO samples were evaluated in term of UV-vis absorption spectra.

Synthesis of Molybdenum Trioxide: Structure Properties and Sensing Film Preparation

In this research, molybdenum trioxide (MoO3) nanoflakes were synthesized by a simple and low cost hydrothermal method for gas sensing application. Sodium molybdate (Na2MoO4·2H2O) was used as the precursor. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). After hydrothermal process, the powders were showed amorphous phase. However, after annealing process the MoO3 was observed as particles having the orthorhombic phase. The average particle sizes of MoO3 nanoflakes were about 80 nm. The morphologies, cross section and elemental compositions of sensing films were analyzed by SEM and EDS line-scan mode analysis. From the SEM image revealed nanoflakes morphologies of MoO3 and the thickness of MoO3 sensing film was about 10 mm. The obtained sensing film can be used as the sensing device to fabricate composited gas sensors for detection of some environmental hazardous gas (including ethanol, carbon monoxide, hydrogen sulfide, sulfur dioxide, nitrogen oxide, and ammonia) will report in the next research.

Photovoltaic Properties of a Conjugated Copolymer Blending with Flame-Made ZnO Nanoparticles

The synthesis, characterizations, and photovoltaic studies of copolymer based on 4,4-dodecylpentaleno[1,2-b]dithiophene (PC12PDT) and 5-octyl-5H-thieno[3,4-c]pyrrole-4,6-dione (TPD) were described. The PC12PDTTPD copolymer achieved a high open circuit voltage (Voc) of ~ 0.8-0.9 V. Bulk-heterojunction (BHJ) solar cells were fabricated by using chlorobenzene with 1% chloronapthalene as the solvent additive. The ZnO nanoparticles, produced by flame spray pyrolysis (FSP), were dispersed in 1-butanol. After that, it was loaded into the devices along with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) used as the electron acceptor. From the results, it was found that the ZnO nanoparticles with different amount had the effect on the power conversion efficiency (PCE) of the solar cells. The PCE obtained in this study (3.33%) was found in the 5.45 wt% ZnO loaded device. This was an improvement as compared to that of the standard device (2.45%).