Nano-silver mediated polymerization of pyrrole: synthesis and gas sensing properties of polypyrrole (PPy)/Ag nano-composite

Thermal polymerization of pyrrole was performed using silver nitrate as source of silver ions followed by its conversion to Polypyrrole (PPy)/Ag nano-comoposites without using any external oxidizing agent or solvent. The formation of PPy was monitored by UV-Visible absorption spectroscopy showing a band at approximately 464 nm. XRD measurement confirmed characteristic peaks for face centered cubic (fcc) silver and presence of PPy at 2 theta of approximately 23 degrees suggesting the formation of PPy/Ag nanocomposite. Transmission electron microscopy (TEM) images showed non-aggregated spherical Ag nano-particles of about 5-10 nm. PPy/Ag thick film acts as a NH3 sensor at 100 degrees C, a H2S sensor at 250 degrees C and CO2 sensor at 350 degrees C. The thick films showed capability to recognize various gases at different operating temperature.     

Electrical,structural and gas sensing properties of zinc phthalocyanine thin films

The dark conductivity of zinc phthalocyanine (ZnPc) has been studied as a function of material purity, crystal phase transformation and temperature with particular regard to gas sensitivity in air, O₂, N₂, argon, NH₃ and NH₃-air mixtures. α-ZnPc was found to grow in the form of randomly oriented micro- crystallites but the β form showed oriented needle-like and whisker growth. The electrical properties were found to be dependent on material purity. Entrainer- sublimed ZnPc showed higher conductivity than impure material and displayed reproducible linear characteristics with less drift and hysteresis.The conductivity of both α- and β-ZnPc is found to be critically dependent on the presence of O₂. The sensitivity to other gases differs for the α and β forms but in both cases NH₃ causes a large dark conductivity decrease, possibly owing to catalytic behaviour, effectively removing oxygen acceptors.Conductivity-temperature data indicate a transition from extrinsic to non-extrinsic conduction for most cases.The conductivity of β-ZnPc is found to be greater than that of α-ZnPc, in contrast with other phthalocyanines.The relative sensitivities to the various gases suggests that ZnPc may be a viable material for selective gas sensing devices.     

Investigation of optical,structural and morphological properties of nanostructured boron doped TiO 2 thin films

Pure and different ratios (1, 3, 5, 7 and 10%) of boron doped TiO₂ thin films were grown on the glass substrate by using sol–gel dip coating method having some benefits such as basic and easy applicability compared to other thin film production methods. To investigate the effect of boron doped on the physical properties of TiO₂, structural, morphological and optical properties of growth thin films were examined. 1% boron-doping has no effect on optical properties of TiO₂ thin film; however, optical properties vary with > 1%. From X-ray diffraction spectra, it is seen that TiO₂ thin films together with doping of boron were formed along with TiB₂ hexagonal structure having (111) orientation, B₂O₃ cubic structure having (310) orientation, TiB_0·024O ₂ tetragonal structure having rutile phase (110) orientation and polycrystalline structures. From SEM images, it is seen that particles together with doping of boron have homogeneously distributed and held onto surface.     

界面聚合法合成苯胺与邻甲氧基苯胺的樟脑磺酸掺杂共聚物及其表征

采用界面聚合法在樟脑磺酸存在的状态下合成了聚苯胺、聚邻甲氧基苯胺以及苯胺与邻甲氧基苯胺的共聚物.利用红外光谱,紫外可见吸收光谱,电子扫描微电镜,X-射线粉末衍射,循环伏安,电导率测试等手段对聚合物进行了表征,初步探讨了单体配比对共聚物形貌、结构及性能的影响.结果表明,界面聚合法合成的上述各聚合物均呈现微米级颗粒状分布,颗粒直径大多在100nm以内;共聚后聚合物的结晶性能下降;循环伏安及电导率测试结果表明,随着聚合物主链中邻甲氧基苯胺结构单元的增加,聚合物的电化学活性及电导率呈下降趋势.     

Structural,morphological, optical and gas sensing properties of pure and Ce doped SnO<Subscript>2</Subscript> thin films prepared by jet nebulizer spray pyrolysis (JNSP) technique

Pure and cerium (Ce) doped tin oxide (SnO₂) thin films are prepared on glass substrates by jet nebulizer spray pyrolysis technique at 450 °C. The synthesized films are characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive analysis X-ray, ultra violet visible spectrometer (UV–Vis) and stylus profilometer. Crystalline structure, crystallite size, lattice parameters, texture coefficient and stacking fault of the SnO₂ thin films have been determined using X-ray diffractometer. The XRD results indicate that the films are grown with (110) plane preferred orientation. The surface morphology, elemental analysis and film thickness of the SnO₂ films are analyzed and discussed. Optical band gap energy are calculated with transmittance data obtained from UV–Visible spectra. Optical characterization reveals that the band gap energy is found decreased from 3.49 to 2.68 eV. Pure and Ce doped SnO₂ thin film gas sensors are fabricated and their gas sensing properties are tested for various gases maintained at different temperature between 150 and 250 °C. The 10 wt% Ce doped SnO₂ sensor shows good selectivity towards ethanol (at operating temperature 250 °C). The influence of Ce concentration and operating temperature on the sensor performance is discussed. The better sensing ability for ethanol is observed compared with methanol, acetone, ammonia, and 2-methoxy ethanol gases.     

Effect of In incorporation on the structural, electrical, and gas sensing properties of ZnO films

In this paper, we report some comparative results on the structural, electrical, and gas sensing properties of undoped, In-doped ZnO, and ZnO–In₂O₃ thin films, respectively. The oxide films were obtained by thermal oxidation (flash oxidation) of metallic films, deposited by thermal evaporation under vacuum. X-ray diffraction patterns reveal that oxidized films are polycrystalline, the crystallites being preferentially oriented with (002) planes parallel with the substrate. It was observed that the films’ morphology, investigated by atomic force microscopy and scanning electron microscopy, is influenced by the In amount. The temperature dependence of electrical conductivity was studied and obtained results indicate that In-doped ZnO and ZnO–In₂O₃ films exhibit an enhancement of electrical conductivity with four orders of magnitude by comparison with undoped ZnO film. Gas sensitivity measurements were performed for four different gases (ammonia, methane, acetone, and ethanol), and it was observed that all investigated films are more sensitive to ammonia. Also, it was observed that gas sensitivity is visibly increased for In-doped ZnO and ZnO–In₂O₃ samples by comparison with undoped ZnO film.     

BiFeO3 films doped in the A or B sites: effects on the structural and morphological properties

Metal-Organic Chemical Vapor Deposition (MOCVD) has been applied to the fabrication of BiFeO3 films undoped and doped with Ba or Ti on SrTiO3 (100) and YSZ (100) substrates. The films have been deposited using a multi-metal source, consisting of the Bi(phenyl)3, Fe(tmhd)3 and Ba(hfa)2 tetraglyme or Ti(tmhd)2(O-iPr)2 (phenyl = -C6H5, H-tmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = iso-propoxide; H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = CH3O(CH2CH2O)4CH3) precursor mixture. The structural and morphological characterization of films has been carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Chemical compositional studies have been performed by energy dispersive X-ray (EDX) analysis. Structural and morphological characterizations point to the formation of homogeneous and flat surfaces for both undoped and doped BiFeO3 films.     

The reactor design and comparison of Fenton, electro-Fenton and photoelectro-Fenton processes for mineralization of benzene sulfonic acid (BSA)

A new approach for promoting ferric reduction efficiency using a different electrochemical cell and the photoelectro-Fenton process has been developed. The use of UVA light and electric current as electron donors can efficiently initiate the Fenton reaction. Benzene sulfonic acid (BSA) was the target compound in this study. The parameters investigated to evaluate the reactor design include the electrode working area, electrode distance, energy consumption. Furthermore, the study also contains the intermediates and the mineralization efficiency of electrolysis, Fenton, electro-Fenton and photoelectro-Fenton process. Oxalic acid, the major intermediate of aromatic compound degradation, can complex with ferric ions. Meanwhile, a double cathode reactor could increase the current efficiency by 7%, which would translate to greater ferrous production and a higher degradation rate. Although the current efficiency of an electrode distance 5.5 cm device is 19% higher than 3.0 cm, results show that after 2 h of electrolysis the electronic expense using an electrode gap of 5.5 cm is much higher than 3.0 cm. The final TOC removal efficiency was 46, 64 and 72% using the Fenton, electro-Fenton and photoelectron-Fenton processes, respectively.     

Correlation between structural,morphological, and optical properties of spin-coated Poly (2,5-di(hexyloxy) cyanoterephthalylidene) (CN-PPV) thin films

Journal of Materials Science: Materials in Electronics - Conjugated polymers (CPs) play a major role in optical applications due to their unique properties. In this current work, fluorine-doped tin...     

Chemical synthesis and low temperature electrical transport in polypyrrole doped with sodium bis(2-ethylhexyl) sulfosuccinate

Polypyrrole (PPy) is polymerized by chemical oxidative polymerization in presence of anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (DEHS) as the dopant. The electrical conductivity was optimized in terms of oxidant to monomer molar ratio and polymerization yield was measured for these reactions. We have used ammonium persulphate (APS) as the oxidant for polymerization in this series of experiments. The effect of concentration of oxidant on the electrical conductivity is examined. Chemical synthesis of polypyrrole is supported by FTIR spectrum. The electrical conductivity of doped and undoped polypyrrole has been measured in the temperature range of 10–300 K and is found to increase with rise in temperature. Electrical conductivity of PPy was analyzed in the light of various charge transport models. Analysis of the electrical conductivity data reveals that in the temperature range 60–300 K electrical transport is predominantly governed by power law behaviour given by Kivelson model. However in the low temperature range 10–60 K electrical transport is dominated by the fluctuation assisted mechanism.     

Influence of nitrogen gas flow rate on the structural, morphological and electrical properties of sputtered TiN films

In this work, nanocrystalline titanium nitride (TiN) films have been deposited by reactive DC magnetron sputtering technique on the Si/SiO₂ (100) substrates. The influence of nitrogen gas flow rate [0, 3, 5, 7 and 9 sccm (standard cubic centimeter per minute)] on the structural, morphological and electrical properties of the nanocrystalline TiN films has been studied. As-deposited TiN films have been characterized by using X-ray diffraction (XRD), XPS (X-ray photoelectron spectroscopy), FESEM (field emission scanning electron microscopy) and four point probe resistivity measurement, respectively. The XRD patterns revealed the HCP symmetry for pure Ti (N₂ = 0 sccm) with (002) preferred orientations, and the FCC symmetry for TiN (N₂ = 3, 5, 7 and 9 sccm) films having (111) preferred orientations. The lattice parameters were found to be a = 2.950 ?, c = 4.681? for the Ti (N₂ = 0 sccm) film and a = 4.250Å for the TiN films. The presence of different phases such as TiN and TiO₂ were confirmed by XPS analysis. The FESEM images showed a smooth morphology of the film with columnar grain structures. The grain size of the TiN films was found to decrease from 22 to 15 nm as the nitrogen flow rate is increased from 0 to 9 sccm. The electrical resistivity measurement showed that the resistivity of the film increased from 11 × 10^?6 to 17 × 10^?6 Ohm cm on increasing nitrogen flow rate from 3 to 9 sccm, having the lowest resistivity of 11 × 10^?6 Ohm cm for the film deposited at 3 sccm nitrogen flow.     

Photoluminescence and lasing from deoxyribonucleic acid (DNA) thin films doped with sulforhodamine

Thin solid films of salmon deoxyribonucleic acid (DNA) have been fabricated by treatment with a surfactant and used as host for the laser dye sulforhodamine (SRh). The DNA films have an absorption peak at approximately 260 nm owing to absorption by the nitrogenous aromatic bases. The SRh molecules in the DNA films have absorption and emission peaks at 578 and 602 nm, respectively. The maximum emission was obtained at approximately 1 wt. % SRh in DNA, equivalent to approximately 100 DNA base pairs per SRh molecule. A distributed feedback grating structure was fabricated on a SiO(2)-Si substrate using interference lithography. The grating period of 437 nm was selected, corresponding to second-order emission at the amplified spontaneous emission wavelength of 650 nm. Lasing was obtained by pumping with a doubled Nd:YAG laser at 532 nm. The lasing threshold was 3 microJ, corresponding to approximately 30 microJ/cm(2) or 4 kW/cm(2). The emission linewidth decreased from approximately 30 nm in the amplified spontaneous emission mode to <0.4 nm (instrument limited) in the lasing mode. The slope efficiency of the lasing was approximately 1.2%.     

Effect of Al dopants on the structural,optical and gas sensing properties of spray-deposited ZnO thin films

Undoped and Al-doped ZnO thin films were deposited on glass substrates by the spray pyrolysis method. The structural, morphological and optical properties of these films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–Vis spectroscopy, photoluminescence (PL) and photoconductivity (PC) measurements, respectively. XRD analyses confirm that the films are polycrystalline zinc oxide with the hexagonal wurtzite structure, and the crystallite size has been found to be in the range 20–40 nm. SEM and AFM analyses reveal that the films have continuous surface without visible holes or faulty zones, and the surface roughness decreases on Al doping. The Al-doped films have been found to be highly transparent (>85%) and show normal dispersion behavior in the wavelength range 450–700 nm. The doped films show only ultraviolet emission and are found to be highly photosensitive. Among all the films examined, at 300 °C the 1.0 at% Al-doped film shows the selective high response (98.2%) to 100 ppm acetone concentration over to methanol, ethanol, propan-2-ol, formaldehyde and hydrogen.     

Size dependent structural, optical and morphological properties of ZnS:Cu thin films

ZnS:Cu thin films have been deposited on glass substrate by a simple neutral pH solution synthesis route and chemical bath deposition technique. The copper concentration was varied between 0 and 0.1 M%. The X-ray diffraction and scanning electron microscope studies show the average size of the nanoparticles are below 4 nm (Bohr diameter). The effect of film thickness on the optical and structural properties has been studied. The optical absorption studies show the band gap energy of ZnS:Cu films decreases from 3.68 to 3.43 eV as thickness varied from 318.3 to 334.1 nm. The structural estimation shows the variation in particle size from 2.67 to 3.14 nm with thickness. The insignificant change in band gap may be due to the increase in particle size and quantum size effect.     

A study of the influences of transition metal (Mn,Ni) co-doping on the morphological,structural and optical properties of nanostructured CdO films

In this paper, a systematic investigations on the effects of transition metals such as Mn and Ni-dopant on physical properties of cadmium oxide (CdO) thin films coated on soda lime glass substrates by using SILAR method have been reported. The characterizations of un-doped, Mn-doped (Cd_0.99 Mn_0.01O) and Mn/Ni double doped CdO [(Cd_0.99?xMn_0.01Ni_xO)(0?≤?x?≤?0.001)] films were investigated by SEM, EDX, XRD and UV–Vis spectrophotometry to determine the morphological, structural and optical properties, respectively. SEM analysis showed that the surface morphologies of the CdO films were influenced by Mn doping and Mn/Ni co-doping. The EDX result verified the presence of expected elements Cd, O, Mn and Ni in the growing solution. The crystal phases of the samples and their crystallinity quality have been investigated by XRD measurements. The X-ray diffractograms show all the diffraction peaks are highly intense also they demonstrate the preferential orientations of (111) and (200) directions. Optical investigations revealed red shift with Mn doping and Mn/Ni co-doping in the absorbance spectrum.     

Structural,chemical, morphological and optical properties of thin films based on potassium bis(2-methyllactato) borate hemihydrate doped by iodine

Journal of Materials Science: Materials in Electronics - Complex composite films of potassium bis(2-methyllactato) borate hemihydrate (KMB) doped with iodine (I2) were dip-synthesized on glass...     

Synthesis and study of the structure,magnetic, optical and methane gas sensing properties of cobalt doped zinc oxide microstructures

Undoped and Cobalt (Co) doped zinc oxide (ZnO & CZx) nanoparticles were synthesized by Solvothermal method. The samples were studied by X-Ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), UV–Vis spectroscopy and Scanning and Transmission Electron Microscopy (SEM & TEM). Moreover the gas sensing properties of the nanoparticles for methane gas took place. Purity of the samples and Co concentration was investigated by EDS and ICP spectroscopy respectively. XRD results described the hexagonal wurtzite structure for all the samples in which crystallinity and the crystallites size decreased with increase of Co doping level. Using UV–Vis spectroscopy the band gap energy was evaluated and redshift of band gap energy was observed by increasing of Co concentration. SEM images demonstrated that nanoparticles were agglomerated with increase of Co doping level. TEM images revealed the nanoparticles size in the range 11–44 nm. Methane sensing properties was enhanced after Co doping of the ZnO nanoparticles for Co concentration up to 4%.     

On the structural, morphological, optical and electrical properties of sol-gel deposited ZnO:In films

Indium-doped zinc oxide thin films deposition was performed by the sol-gel technique using homogeneous and stable solutions of zinc acetate 2-hydrate and indium chloride in ethanol. Films were spin coated onto glass substrates. After drying and after a heat treatment at 450 °C, highly transparent (80%-90%) films were obtained. The effect on the structural, morphological, optical and electrical thin films properties of the dopant concentration was investigated. The temperature dependencies of the electrical conductivity under vacuum and in open atmosphere were analysed and discussed.