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991.
Hirak K. Patra 《Analytica chimica acta》2009,649(1):128-134
A real time multimodal data acquisition imaging setup is developed for the electrophoretic movement of plasmonic nanoparticles. Movement of the nanoparticles is recorded by time-lapse digital imaging at 8-megapixel resolutions. The analysis of the moving nanoparticle band is performed using threshold image and color extraction at respective time frames. The migration dynamics is sensitive to size, nature and the extent of the surface conjugation to the nanoparticle. The dynamics of color intensity of the nanoparticles is shown to be dependent on the extent of stabilization of nanoparticle (by a given agent). The stability of nanoparticle is determined by stationary nature and also the relative proportions of pixel intensities in respective color planes (R, G and B). Detergents stabilize nanoparticles in a concentration dependent fashion. In case of neutral polymers the extent of stabilization depends on the relative proportion of the polymer and also on the nature of the same, e.g., PEG (polyethylene glycol) at low concentration imparts higher stability as compared to PVP (polyvinylpyrilidone). The ascending or declining temporal dynamics of color profiles observed in case of citrate stabilized or amino acid conjugated nanoparticles, represent enrichment of plasmonic particles, or their diffusion resulting from loss of charge during migration. The higher dimensional imaging technique thus can be exploited for discriminating the nanoparticles on the basis of their migration behavior and their stability as reflected from color dynamics. The technique is applicable to other nano-sized colored objects, e.g. proteins like hemoglobin where the protein color has important clinical value. 相似文献
992.
993.
Dielectric Relaxation Studies of Binary Mixture of α‐Picoline and Methanol Using Time Domain Reflectometry at Different Temperatures 下载免费PDF全文
Complex permittivity spectra of binary mixtures of varying concentrations of α‐picoline and methanol (MeOH) were obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15 K, 288.15 K, 293.15 K and 298.15 K temperatures. The dielectric relaxation parame‐ ters namely static permittivity (σ0), high frequency limit permittivity (σoo1) and the relaxation time (ρ) were determined by fitting complex permittivity data to the single Debye/Cole‐Davidson model. Complex non linear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess static permittivity (σ0E) and the excess inverse relaxation time (1/ρ)E which contains information regarding mo‐ lecular structure and interaction between polar — polar liquids, were also determined. From the experimental data, effective Kirkwood correlation factor (geff) and Bruggeman factor (fB) were calculated. Excess parameters were fitted to the Redlich‐Kister polynomial equation. The values of static permittivity and relaxation time increase non‐linearly with increase in the mol fraction of MeOH at all temperatures. The values of excess static permittivity (σ0E) and the excess inverse relaxation time (1/ρ)E are negative for the studied α‐picoline — MeOH system at all temperatures. 相似文献
994.
Analysis of nitrogenous organic compounds from mainstream cigarette smoke using low‐temperature solvent extraction followed by comprehensive two‐dimensional gas chromatography with high‐resolution time‐of‐flight mass spectrometry 下载免费PDF全文
Zhangmin Xiang Kai Cai Shuping Zhou Zhaoliang Geng Wenjie Pan 《Journal of separation science》2015,38(15):2655-2663
A method involving comprehensive two‐dimensional gas chromatography coupled to high‐resolution time‐of‐flight mass spectrometry was developed and applied to the analysis of nitrogenous organic compounds present in mainstream cigarette smoke trapped on self‐designed equipment. The samples were prepared using low‐temperature solvent extraction under liquid nitrogen and analyzed by comprehensive two‐dimensional gas chromatography with high‐resolution time‐of‐flight mass spectrometry. Important experimental parameters, such as the type and volume of the extraction solvent and flow rate of smoking, were optimized to improve the analysis parameter. The results indicated that 180 mL of diethyl ether in the low‐temperature solvent extraction apparatus system with a 4 mL/min smoke flow rate were the optimal conditions. Then, 85 nitrogenous organic compounds were identified and quantified using a mass spectral library search, accurate mass ion and N‐rules of a molecular formula for nitrogen compounds. Finally, a comparison of the low temperature solvent extraction method and Cambridge filter pad method indicated that more peaks, a higher peak volume and better repeatability were obtained using the low‐temperature solvent extraction method. 相似文献
995.
Thangaraj Anand Gandhi Sivaraman Murugan Iniya Ayyanar Siva Duraisamy Chellappa 《Analytica chimica acta》2015
Chemosensors based on aminobenzohydrazide Schiff bases bearing pyrene/anthracene as fluorophores have been designed and synthesized for F− ion recognition. The addition of fluoride ions to the receptors causes a dramatically observable colour change from pale yellow to brown/red. 1H NMR studies confirm that the F− ion facilitates its recognition by forming hydrogen bond with hydrogens of amide and amine groups. Moreover these sensors have also been successfully applied to detection of fluoride ion in commercial tooth paste solution. 相似文献
996.
Shimaa A. Atty Mona A. Mohamed Lobna M. AbdElHalim Fatma A. Fouad Rabah Boukherroub 《Electroanalysis》2019,31(7):1215-1223
A simple and efficient procedure is described for the electrochemical determination of ledipasvir (LDP) in presence of co‐formulated drug sofosbuvir (SOF). Herein, a highly sensitive, low‐cost electrochemical protocol was utilized to fabricate a zeolite modified carbon paste electrode (ZY/CPE) through mixing of zeolite nanostructures with graphite powder. The fabricated sensor displayed high sensitivity, allowing optimal charge transfer/electrode kinetics. Different experimental and chemical factors, including electrode composition, effect of pH, scan rate and amount of ZY were evaluated carefully to obtain the highest electrochemical response. Under optimized conditions and using square wave voltammetry (SWV), the current response of the ZY/CPE electrochemical sensing platform exhibited a detection limit of 7.5×10?9 M and a large linear range from 5.0×10?8 to 1.0×10?4 M. The practical applicability of the suggested electrochemical platform was verified in the assessment of LDP in pharmaceutical formulations with excellent recoveries in the range of 99.50–98.87 %. Moreover, a biological relevance of the developed sensor was established by the analysis of LDP in human urine and plasma samples with satisfactory recoveries of 99.00 and 99.68 %, respectively. Due to the simplicity and ease of preparation of the proposed sensor, it can be used in quality control laboratories and for clinical analysis. 相似文献
997.
Femtosecond Time-Resolved Spectroscopic Photoemission Electron Microscopy for Probing Ultrafast Carrier Dynamics in Heterojunctions 下载免费PDF全文
Bo-han Li Guan-hua Zhang Yu Liang Qun-qing Hao Ju-long Sun Chuan-yao Zhou You-tian Tao Xue-ming Yang Ze-feng Ren 《化学物理学报(中文版)》2019,32(4):399-405
The fast developing semiconductor industry is pushing to shrink and speed up transistors. This trend requires us to understand carrier dynamics in semiconductor heterojunctions with both high spatial and temporal resolutions. Recently, we have successfully set up a timeresolved photoemission electron microscopy (TR-PEEM), which integrates the spectroscopic technique to measure electron densities at specific energy levels in space. This instrument provides us an unprecedented access to the evolution of electrons in terms of spatial location, time resolution, and energy, representing a new type of 4D spectro-microscopy. Here in this work, we present measurements of semiconductor performance with a time resolution of 184 fs, electron kinetic energy resolution of 150 meV, and spatial resolution of about 150 nm or better. We obtained time-resolved micro-area photoelectron spectra and energy-resolved TR-PEEM images on the Pb island on Si(111). These experimental results suggest that this instrument has the potential to be a powerful tool for investigating the carrier dynamics in various heterojunctions, which will deepen our understanding of semiconductor properties in the submicron/nanometer spatial scales and ultrafast time scales. 相似文献
998.
An efficient fluorescent chemosensor for Hg2+ ion, based on 5-(dimethylamino)-N-(2-mercaptophenyl)naphthalene-1-sulfonamide, has been developed. It exhibits Hg2+-selective on–off fluorescence quenching behavior via twisted intramolecular charge transfer (TICT) mechanism, which is rationalized by time dependent density functional theory (TD-DFT) calculations. The system exhibits visible color change from colorless to gray upon Hg2+ binding with very high selectivity and sensitivity (as low as 5.0 × 10−10 mol L−1) over other metal ions such as K+, Na+, Ag+, Mn2+, Ca2+, Ba2+, Fe2+, Zn2+, Pb2+, Cu2+, Sn2+, Cd2+, Ni2+ and Co2+. The present sensing system is also successfully applied for the detection of Hg2+ ion in real samples. 相似文献
999.
1000.
ZENG XIANCHENG WANG QIAN CHENG SIQING ZHANG YUANQIN 《Journal of Dispersion Science and Technology》2013,34(4):1273-1283
The polymerization of acrylamide in mixed micellar solutions of surfactants, initiated by NaHSO3 has been studied at 20 and 3Q° C with time variable method of thermokinetics for 1. 5-order reaction. The results indicate that the mixed micellar systems of cationic or anionic with zwitterionic surfactants (SLS/ CTAB, SLS/ TTAB, SLS/ SDS) and cationic with nonionic surfactants (Brij 357sol; CTAB, Bri-J35/TTAB, Brij35/ DTAB) have catalytic effect on the polymerization in the order, at 20° C. SLS/ SDS SLS/ TTAB SLS/ CTAB Brij35/ CTAB at 30° C SLS/ SDS SLS/ TTAB≈ / CTAB Bri-j35/ DTAB= sBrij35/ TTAB as Brij35/ CTAB, while Brij35/ SDS mixed micellar system has inhibition. These effects are attributed to the effect of the Stern layer of mixed micelles on the step of initiator (HSOT) to form free radical. 相似文献