Photochemical-spectrofluorimetric method for the determination of benzoylurea insecticides: applications in river water samples and in technical formulations

Effects of ultraviolet (UV) irradiation on ClO4 doped poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were investigated in terms of the structural and thermoelectric properties. The ClO4 doped PEDOT films were synthesized by electropolymerization; subsequently, these films were exposed to UV light for predetermined time intervals in ambient air. UV irradiation led to an agglomeration of PEDOT domains, which in turn causes an increase in the grain size and the surface roughness, as observed in scanning electron microscopy images. Fourier transform infrared spectroscopy revealed that the molecular structure of PEDOT was not affected by UV irradiation. Electron spin resonance (ESR) analysis revealed that the spin density was drastically reduced by short-term UV irradiation of less than 5 min. Upon increasing the UV irradiation time, the spin density gradually increased. A similar relationship was observed between the UV irradiation time and the electrical conductivity. Further, short-term UV irradiation also increased the power factor. The maximum power factor was found to be 1.9 µW/(m·K2) at a UV irradiation time of 2.5 min, this is approximately 60% higher than that of the pristine PEDOT thin film. Therefore, we conclude that the appropriate UV irradiation dosage enhances the thermoelectric performance, but an excess UV irradiation leads to a deterioration of the same.

Electro-optical characteristics of polymer-dispersed liquid crystal containing copper (II) phthalocyanine as a function of UV irradiation time

The impact of ultraviolet (UV) light irradiation on thermally grown SiO2/4H-SiC structures was investigated by characterizing the 4H-SiC metal-oxide-semiconductor (MOS) capacitors fabricated with and without UV irradiation onto the oxide layers. The UV irradiation was found to significantly increase a hysteresis in capacitance-voltage (C-V) characteristics and cause a positive flatband voltage (VFB) shift, suggesting the generation of oxide charges and traps. Since the values of C-V hysteresis and VFB shift depend on the UV irradiation time, the electrical defects were considered to be induced during UV irradiation. In contrast, UV irradiation caused no marked change for the reference Si-MOS capacitors, indicating that the generation of UV-induced electrical defects was an intrinsic property of thermally grown SiO2/SiC structures. A detailed characterization of SiC-MOS capacitors with terraced SiO2 layers revealed that the UV-induced defects were located near the SiO2/SiC interface. The interfacial fixed charge density (QOX) was estimated to be 1.7×1012 cm-2 for the sample with UV irradiation, while that of the sample without UV irradiation was 1.0×1012 cm-2. Also, a slight increase was found in interface state density (Dit) due to UV irradiation. These results imply that the UV-induced defect generation correlates with residual carbon impurities at the SiO2/SiC interface.

By triangular wave method, the polarization currents of an azo-containing banana-shaped antiferroelectric liquid crystal were investigated as a function of the time of 365-nm ultraviolet irradiation. Under the 365-nm irradiation, the polarization currents were observed to evolve with the time of ultraviolet irradiation until they diminished. The roles of photoisomerization, photolysis and thermolysis were discussed for the azo-containing banana-shaped liquid crystal.

Magnet integrated fabric phase sorptive extraction as a stand-alone extraction device for the monitoring of benzoyl urea insecticides in water samples by HPLC-DAD

Solvent influence on crosslinking and surface characteristics of Urushi films

Fluorimetric determination of aromatic pesticides in technical formulations. Effects of solvent and of ultraviolet photolysis

近年来,由农药残留导致的环境污染问题已引起社会的广泛关注,开发便捷高效的分析方法对农药残留进行检测和监测十分必要。研究设计并成功制备了聚多巴胺涂敷的聚酰胺-胺树状分子功能化的二氧化硅复合材料(SiO2-PAMAM-PDA),并采用透射电镜对其进行表征。开发了以此复合材料为吸附剂的分散微固相萃取方法(D-μ-SPE),并结合高效液相色谱对水基质中的4种苯甲酰脲类杀虫剂(BUs)残留进行了富集检测。多巴胺结构中含有丰富的苯环、氨基及羟基,可与目标物形成氢键、π-π相互作用,从而增强了材料对苯甲酰脲的萃取能力。对吸附剂用量、萃取时间等可能影响萃取效率的条件进行了单因素优化。在最优条件下,该方法的线性范围在10~500 μg/L之间,根据3倍信噪比(S/N)计算所得的检出限(LOD)为1.1~2.1 μg/L,回收率为82.8%~94.1%,相对标准偏差(RSD)为2.1%~8.0%。将建立的方法与已报道的以苯甲酰脲作为目标物的方法进行了对比,发现方法样品用量及萃取剂用量均较少,且所需前处理时间较短,有机溶剂消耗也较少,为苯甲酰脲类农药的检测提供了更快速、绿色的选择。为评估所开发方法的实际样品适用性,将其应用于3种河水样品中4种苯甲酰脲类杀虫剂的分析检测,所得回收率及RSD分别为69.5%~99.4%和0.2%~9.5%,表明此方法在实际样品中同样具有较高的准确性和精密度。

Photochemical-fluorimetric method for the determination of total chlorophenoxyacid herbicides

The bandwidth broadening of polymer-stabilised cholesteric liquid crystal (PSLC) has the potential to enhance its optical performance. In this study, a novel approach was presented for preparing broadband reflective films by using nanofibers loaded with zinc oxide nanoparticles as network supports in chiral nematic liquid crystals. The introduction of nanofiber played a pivotal role in replacing some monomers, resulting in cost-efficiency. Experiments were conducted to investigate the influence of different compositions and conditions on the broadband reflection performance. Specially, the effect of the concentration of nanoparticles loaded in nanofibers, direct-current (DC) voltage, monomer content, ultraviolet (UV) light intensity, polymerisation temperature, and UV irradiation time were examined. The microstructure of nanofiber and optical texture of PSLC were characterised using SEM and POM, respectively. With the above optimisations, the broadening from 246 nm to 412 nm was achieved and the films embodied brilliant UV shielding and infrared (IR) heat control effectiveness. This study provides a potential method for the preparation of smart liquid crystal devices in the future.

Non-ribosomal peptide synthetases (NRPSs) biosynthesize many pharmaceuticals and virulence factors. The biosynthesis of these natural peptide products from biosynthetic gene clusters depends on complex regulations in bacteria. However, our current knowledge of NRPSs is based on enzymological studies using full NRPS systems and/or a single NRPS domain in heterologous hosts. Chemical and/or biochemical strategies to capture the endogenous activities of NRPSs facilitate studies on NRPS cell biology in bacterial cells. Here, we describe a chemical scaffold for the rapid and selective photoaffinity labelling of NRPSs in purified systems, crude biological samples and living bacterial cells. We synthesized photoaffinity labelling probes coupled with 5'-O-N-(phenylalanyl)sulfamoyladenosine with clickable alkyl diazirine or trifluoromethyl phenyl diazirine. We found that a trifluoromethyl phenyl diazirine-based probe cross-linked the Phe-activating domain of a GrsA-NRPS with high selectivity and sensitivity at shorter ultraviolet (UV) irradiation times (less than 5 min) relative to a prototypical benzophenone-based probe. Our results demonstrated that this quick labelling protocol can prevent damage to proteins and cells caused by long UV irradiation times, providing a mild photoaffinity labelling method for biological samples. This article is part of the theme issue 'Reactivity and mechanism in chemical and synthetic biology'.

We focused on the antimicrobial effects of titanium dioxide (TiO2) after stopping ultraviolet (UV) irradiation as an adjunctive treatment for peri-implantitis in this study. The aim was to determine the continuous photocatalytic effects of TiO2 after UV irradiation and its antimicrobial activity against periodontal pathogen. The continuous photocatalytic effects of TiO2 after UV irradiation were determined by electron spin resonance (ESR) spectroscopy using TiO2 particles of various sizes with various UV irradiation times. In addition, antimicrobial activity against Porphyromonas gingivalis was investigated by quantitation of colony-forming units (CFUs). The results showed that the ESR signal ratio for the UV-irradiated TiO2 was significantly higher than that of the non-irradiated TiO2. UV-irradiated TiO2 significantly reduced the number of P. gingivalis when compared with non-irradiated controls. These results suggest that TiO2 has a continuous photocatalytic effect even after stopping UV irradiation and that it showed antimicrobial activity against periodontal pathogen.

Silver nanowires (AgNWs) are used as transparent electrodes (TE) in many devices. However, the contact mode between the nanowires is the biggest reason why the sheet resistance of silver nanowires is limited. Here, simple and effective ultraviolet (UV) irradiation welding is chosen to solve this problem. The influence of the power density of the UV irradiation on welding of the silver nanowires is studied and the fixed irradiation time is chosen as one minute. The range of the UV (380 nm) irradiation power is chosen from 30 mW/cm2 to 150 mW/cm2. First of all, the transmittance of the silver nanowire film is not found to be affected by the UV welding (400–11,000 nm). The sheet resistance of the silver nanowires decreases to 73.9% at 60 mW/cm2 and increases to 127.6% at 120 mW/cm2. The investigations on the UV irradiation time reveal that the sheet resistance of the AgNWs decreases continuously when the UV irradiation time is varied from 0 to 3 min, and drops to 57.3% of the initial value at 3 min. From 3–6 min of the continuous irradiation time, the change of the sheet resistance is not obvious, which reflects the self-limiting and self-termination of AgNWs welding. By changing the wavelength of the UV irradiation from 350–400 nm, it is found that the welding effect is best when the UV wavelength is 380 nm. The average transmittance, square resistance, and the figure of merit of the welded AgNWs at 400–780 nm are 95.98%, 56.5 Ω/sq, and 117.42 × 10−4 Ω−1, respectively. The UV-welded AgNWs are also used in silicon-based photodetectors, and the quantum efficiency of the device is improved obviously.

Evaluation of the control of mosquitoes with insect growth regulators.

Fluorimetry and photochemically induced fluorimetry (PIF) are proposed for the quantitative analysis of four psychotropic drugs, including ethopropazine (EPZ), levomepromazine (LPZ), thioproperazine (TPZ) and trifluoperazine (TFZ). The influence of ultraviolet (UV) irradiation time on the fluorescence excitation and emission wavelengths and intensity was investigated in aqueous buffer solutions (pH 4 – 6) at room temperature (298 K). The selected UV irradiation times were between 10 and 50 s, depending on the compound. Linear calibration graphs were established over about two to four orders of magnitude, with relative standard deviations in the range 2.0 – 5.4%. PIF limits of detection were comprised between 2.6 and 8 ng ml−1, depending on the compound. The PIF method was found to be more sensitive and more reliable than conventional fluorimetry for the phenothiazine derivatives under study. PIF was applied to the determination of these compounds in urine and pharmaceutical samples. The mean recoveries ranged from 88 to 119%. bOn leave from the Departement of Analytical Chemistry, Faculty of Sciences, University of Extremadura, Badajoz (Spain).