The crystal‐plane effect of ZnO nanostructures on the toxic 2‐chlorophenol gas‐sensing properties was examined. Three kinds of single‐crystalline ZnO nanostructures including nanoawls, nanorods, and nanodisks were synthesized by using different capping agents via simple hydrothermal routes. Different crystal surfaces were expected for these ZnO nanostructures. The sensing tests results showed that ZnO nanodisks exhibited the greatest sensitivity for the detection of toxic 2‐chlorophenol. The results revealed that the sensitivity of these ZnO samples was heavily dependent on their exposed surfaces. The polar (0001) planes were most reactive and could be considered as the critical factor for the gas‐sensing performance. In addition, calculations using density functional theory were employed to simulate the gas‐sensing reaction involving surface reconstruction and charge transfer both of which result in the change of electronic conductance of ZnO. 相似文献
Polyaniline (PANI) was prepared by the chemical oxidative polymerization of aniline, and ZnO, with the mean particle size of 28 nm, was synthesized by a non-aqueous solvent method. The organic-inorganic PANI/ZnO hybrids with different mass fractions of PANI were obtained by mechanically mixing the prepared PANI and ZnO. The gas sensing properties of PANI/ZnO hybrids to different volatile organic compounds (VOCs) including methanol, ethanol and acetone were investigated at a low operating temperature of 90°C. Compared with the pure PANI and ZnO, the PANI/ZnO hybrids presented much higher response to VOCs. Meanwhile, the PANI/ZnO hybrid exhibited a good reversibility and a short response-recovery time, implying its potential application for gas sensors. The sensing mechanism was suggested to be related to the existence of p-n heterojunctions in the PANI/ZnO hybrids. 相似文献
Present paper mainly focuses on the synthesis, characterization polyindole-ZnO nano composites for third order nonlinear optical applications. Polyindole was synthesized through oxidative polymerization technique and its composites were prepared with different ZnO concentration. Structural morphology of the polymer composite was studied using FESEM, XRD and UV Visible spectroscopic technique. Polymer showed broad absorption with absorption maxima of 395 nm. Newly prepared thin films showed excellent nonlinear absorption with very good optical limiting behaviour when it is exposed to He-Ne laser with maximum optical limiting power of 11 mW along with third-order nonlinear susceptibility χ(3) of 2.72 × 10?3 esu. Hence these polymer composites may be potential candidate for optical limiting applications. 相似文献
1D ZnO rods are synthesized using less explored hydrazine method. Here we find, besides being combustible hydrazine can also be used as a structure-directing agent. The ratio of zinc nitrate (ZN) to hydrazine is found to control the morphology of ZnO. At lower concentration of ZN as compared with hydrazine the morphology of ZnO is found to be spherical. As we increase the hydrazine content the morphology changes from spherical (diameter 100 nm) to the elongated structures including shapes like Y, T as well dumbbell (diameter 40 nm and length 150 nm). Interestingly for more than 50% of hydrazine ZnO micro-rods are formed. Such rods are of diameter 120 nm having length of about 1 μm for ZN to hydrazine ratio of 1:9, isolated as well as bundle of rods are seen in scanning electron microscopy (SEM). The X-ray diffraction (XRD) reveals the phase formation with average particle size of 37 nm as calculated using Scherrer's formula. The high-resolution transmission electron microscopy (HRTEM) is also done to confirm the d-spacing in ZnO. Gas sensing study for these samples shows high efficiency and selectivity towards LPG at all operating temperatures. Photoluminescence (PL) study for these samples is performed at room temperature to find potential application as photoelectric material. 相似文献
In the present investigation, ZnO nanoflakes was prepared via sonochemical synthesis route. Effect of ultrasonic treatment time was studied based on structural, morphological and optical properties. X-ray diffraction (XRD) reveals the formation of wurtzite hexagonal crystalline structure of ZnO nanoflakes. Ultrasonic treatments affected the crystallite size and the density of dislocation, which is due to increased nucleation and growth rates of nanoflakes. The samples synthesized at 40–50 min ultrasonic treatment showed a strong absorption band at 605 and 650 (cm?1) versus other treatments, which is an indication of 2D nanostructure (nanoflakes). FE-SEM analysis further confirms the formation of 2D nanostructures of the ZnO. The composition and purity was confirmed by the energy dispersive X-ray (EDX) analysis, which displays the occurrence of Zn and O elements in the sample. Photocatalytic activity (PCA) of ZnO nanoflakes was studied for methyl orange (MO) dye degradation under UV light exposure and up to 93.13 % dye degradation is achieved within 90 min. Effect of various parameters (dye concentration, mass of photocatalytic material) and kinetic study was also performed. Results revealed that the ultrasonic treatment affected the optical and photocatalytic properties of the of ZnO nanoflakes, which could be employed for the remediation of dyes in textile effluents. 相似文献
A new and efficient one-pot synthesis of cyanoferrocene from ferrocenecarboxaldehyde is described by employing the NH2OH · HCl/KI/ZnO/CH3CN system. 相似文献
A simple, efficient and economically viable method for the Heck reaction has been accomplished in the absence of phosphine ligand. The Heck reaction was performed using nanostructured Ni-Co/ZnO material as a heterogeneous catalyst in a DMF/H2O solvent system and in the presence of K2CO3, at 120 °C. The Ni-Co/ZnO nanostructures were prepared by the facile reduction-impregnation method. The structural and morphological properties of Ni-Co/ZnO nanostructure were investigated using various physico-chemical characterization techniques. Structural studies displayed the formation of hexagonal (wurtzite) ZnO. Electron microscopy imaging showed the presence of agglomerated clusters of Ni-Co nanoparticles over the surfaces of elliptical, flower bud-like and irregularly shaped sub-micron sized particle bundles of ZnO. The elemental composition analysis (EDX) confirmed the loading of Ni and Co nanoparticles over the nanocrystalline ZnO. The surface chemical state analysis of Ni-Co/ZnO material validated that Ni nanostructure exists in Ni2+ and Ni3+ species, whereas, Co nanostructure exists in Co2+ and Co3+ species. UV–Vis diffuse reflectance spectroscopy displays red shift in the light absorption edge of Ni-Co/ZnO catalyst compared to pure ZnO. The as-prepared Ni-Co bimetallic supported ZnO nanostructure showed better catalytic activity and stability for the Heck reactions under phosphine ligand-free conditions. Ni-Co/ZnO catalyzed Heck reactions afforded the corresponding cross-coupled products with moderate to good yields (up to 92%). Ni-Co/ZnO catalyst could be reused for five successive runs without significant loss of catalytic activity. 相似文献
We have investigated reverse saturable absorption (RSA) of tetrakis(2,9,16,23-tert-butyllanthanide bisphthalocyanines)(M(TBPc)2, M=Lu, Dy, Tb) with Z-scan technique. Furthermore, lanthanide bisphthalocyanines have also been utilized for optical switches based on their RSA performance. However, the experimental results reveal that the performances of RSA and optical switches for M(TBPc)2 (M=Lu, Dy, Tb) are poorer than that of tetrakis(2,9,16,23-tert-butylcopper phthalocyanines) (Cu(TBPc)) due to strong intramolecular π-π interaction between the two Pc rings. 相似文献
Experimental density and the refractive index of the ternary mixture acetone + n-hexane + water, and their binary systems were experimentally measured and correlated at 298.15 K and atmospheric pressure. A maximum in refractive indices has been observed for the acetone + water system while the excess molar volume and the molar refraction change are all negative. For the mixture acetone + n-hexane, the excess molar volume is always positive and the molar refraction change of mixing showed a S-shaped dependence on acetone composition. The excess molar volumes and molar refraction changes of mixing were correlated using the Redlich-Kister expression and Cibulka equation. The coefficients and standard deviation between the experimental and fitted values were estimated. Good agreement between both results was obtained. 相似文献
In this paper, the damage process was investigated on the 170 keV proton-irradiated polyimide, based on the evolution of free radical and its correlation with degradation of the optical transmittance using electron paramagnetic resonance (EPR) and optical-transmittance measurements. The results indicate that the g value of irradiated free radicals keeps at a constant of 2.0025 but the spectral intensity of the free radicals increased with the increasing proton fluence. It is found that during the post-storage after irradiation, the concentration of free radical decreased in an exponential rule with the post-storage time and the free-radical stability can be defined by the corresponding time constant at around 2.3 h. It is interested that the recovery of optical-transmittance follows the same mode as that of free radicals. The mechanisms on the free-radical evolution and the correlation between free radical and optical property are discussed in the paper. 相似文献
Chemical sensing, imaging and microscopy based on the use of fluorescent probes has so far been limited almost exclusively
to the detection of a single parameter at a time. We present a scheme that can overcome this limitation by enabling optical
sensing of two parameter simultaneously and even at identical excitation and emission wavelengths of two probes provided (a)
their decay times are different enough to enable two time windows to be recorded, and (b) the emission of the shorter-lived
probe decays to below the detectable limit while that of the other still can be measured. We refer to this new scheme as the
dual lifetime determination (DLD) method and show that it can be widely varied by appropriate choice of probes and experimental
settings. DLD is demonstrated to work by sensing oxygen and temperature independently from each other by making use of two
probes, one for oxygen (a platinum porphyrin dissolved in polystyrene), and one for temperature [a europium complex dissolved
in poly(vinyl methylketone)]. DLD was applied to monitor the consumption of oxygen in the glucose oxidase-catalyzed oxidation
of glucose at varying temperatures. The scheme is expected to have further applications in cellular assays and biophysical
imaging.
Figure Principle behind the dual lifetime determination (DLD) method 相似文献
In this paper, we report the synthesis of a series of porphyrins, designed as photodynamic therapy (PDT) agents, substituted by three glycosyl units linked by a triazole group to chromophore in the aim to target tumor cells overexpressing lectin-type membrane receptors, by ‘click-chemistry’ under microwave heating. 相似文献
Blends of polymethylmethacrylate (PMMA) and diblock methacrylic azopolymers have been investigated for holographic storage with short light pulses. Transmission electron microscopy measurements show that the dilution of the block copolymer in PMMA changes the microstructure from a lamellar to a spherical morphology. Besides the optical anisotropy induced with linearly polarized 488 nm light is smaller and less stable in the blends than in the block copolymer films. Holographic gratings induced with light pulses of 1 s are not as stable as the ones achieved with writing times of several minutes (both in the blend and in the block copolymer) but a final efficiency remains. Up to 20 polarization gratings have been multiplexed, using light pulses of 1 s, 300 ms and 100 ms, in thick (500 μm) blend films. The equilibrium values of the efficiencies are higher than 10−5 for all the gratings. An angular resolution of about 0.5° has been achieved in these thick gratings. 相似文献
A small-scale adiabatic calorimeter has been constructed as part of a larger project to study the thermodynamics of nanomaterials and to facilitate heat capacity measurements on samples of insufficient quantity to run on our current large-scale adiabatic apparatus. This calorimeter is designed to measure the heat capacity of samples whose volume is less than 0.8 cm3 over a temperature range of T = 13 K to T = 350 K. Heat capacity results on copper, sapphire, and benzoic acid show the accuracy of the measurements to be better than ±0.4% for temperatures higher than T = 50 K. The reproducibility of these measurements is generally better than ±0.25%. 相似文献
This template will self‐destruct : A unique particle‐growth mechanism involves growth of new coordination polymers on the surface of initially formed hexagonal blocks and concomitant dissolution of the blocks to form hexagonal tubes (see scheme and scanning electron, optical, and fluorescence microscopy images). Calcination of the tubes yields ZnO particles of the same shape.
The speed of sound in liquid cyclopentane, cyclohexane, methylcyclopentane and methylcyclohexane were measured, with a sing-around technique operated at a frequency of 2 MHz, at temperatures from (283 to 343) K and pressures up to 20 MPa with an estimated error of less than ± 0.2 per cent in the high-density region. From these measurements the densities and isobaric and isentropic compressibilities of each compound were estimated. The behaviour on the temperature and pressure in these quantities is discussed based on the difference in molecular shape between cyclic and normal alkanes with those for n-alkanes. 相似文献
One of the most severe environmental problems is heavy metal contamination, putting the world's sustainability at risk. Much effort has been put into developing sensors that can be taken anywhere to detect the environmental effects of heavy metals. Sensitivity, selectivity, multiplexed detection ability, and mobility enhance significantly when nanoparticles and nanostructures are incorporated into sensors. LDHs (layered double hydroxides) have gotten much attention in analytical chemistry in recent years because of their benefits, including their large specific surface area, ease of synthesis, low cost, and high catalytic efficiency and biocompatibility. LDHs are often manufactured as nanomaterial composites or created with specialized three-dimensional structures depending on the application. However, in these settings, LDHs (as color indicators, extracting sorbents, and electrochemical sensing) are usually restricted. Upcoming signs of progress and development possibilities of LDHs in analytical chemistry are reviewed in this paper to assist overcome these problems. Furthermore, the approaches used in the design of LDHs, including structural aspects, are defined and assessed in preparation for future analytical applications. The latest advances in optical and electrochemical sensors to detect heavy metals are described in this review. The sorts and characteristics of LDHs will be explored first. We will then go into microelectrode (or nanoelectrode) arrays, nanoparticle-modified electrodes, and microfluidic optical and electrochemical sensing assays in detail. This paper also discusses design strategies for LDH-based nanostructured sensors and the advantages of using nanomaterials and nanostructures. 相似文献
Quantum cascade lasers (QCLs) are a relatively new type of semiconductor laser operating in the mid- to long-wave infrared. These monopolar multilayered quantum well structures can be fabricated to operate anywhere between 3.5 and 20 microm, which includes the molecular fingerprint region of the infrared. This makes them an ideal choice for infrared chemical sensing, a topic of great interest at present. Frequency stabilization and injection locking increase the utility of QCLs. We present results of locking QCLs to optical cavities, achieving relative linewidths down to 5.6 Hz. We report injection locking of one distributed feedback grating QCL with light from a similar QCL, demonstrating capture ranges of up to +/-500 MHz, and suppression of amplitude modulation by up to 49 dB. We also present various cavity-enhanced chemical sensors employing the frequency stabilization techniques developed, including the resonant sideband technique known as NICE-OHMS. Sensitivities of 9.7 x 10(-11) cm(-1) Hz(-1/2) have been achieved in pure nitrous oxide. 相似文献