Communication-Ultrafast Anodized Titania Nanotube Arrays Loaded with Quantum Dots via Ultrasonic Assistance

Self-aligned and firmly-structured titania nanotube arrays (TNAs) with excellent photoelectric response were fabricated by anodization in tens of seconds. Furthermore, TNAs were decorated with CdS quantum dots by ultrasonic-assisted successive ionic layer adsorption and reaction (U-SILAR) method. The resulted CdS/TNAs hybrid shows higher visible light absorption, stronger photo current and stable structure than those of the sample by traditional SILAR method. © 2016 The Electrochemical Society. [DOI: 10.1149/2.0341609jss] All rights reserved. Great efforts have been made to produce titania nanotube arrays (TNAs) by electrochemical anodization method due to its unique advantages. 1-3 Normally, one or more hours are needed to grow TNAs with a length of several micrometers. Quantum dots (QDs) can be easily synthesized and attached on TNAs by successive ionic layer adsorption and reaction (SILAR) method. 9,10 However, the disadvantages of the method are obvious, e.g. the uncontrollable uniformity and dispersion of QDs and the weak adhesion of the QDs on TNAs, etc. In this work, a new approach using ultrasonic-assisted SILAR (U-SILAR) is developed to improve the QDs/TNAs hybrid structures. We found that the QDs could be well distributed throughout the tubes and firmly adhered on TNAs. The transient photoelectric response was investigated. Experimental Titanium foils (0.1 mm in thickness, 99.6% purity) were anodized by an electrochemical setup which consists of Interlock potentiostatgalvanostat (IPD-12003SLU) and a classical two-electrode cell. The electrolyte contains 0.4 M NH 4 F dissolved in a solution of ethylene glycol and DI water (30:1 volume ratio). The anodization was performed at 120 V without stir at 10 • C for 4, 20, 40, 60, and 80s, respectively. The samples were named as TNA120 series. As a reference, another series of samples were prepared at 60 V in the electrolyte which contains 0.27 M NH 4 F dissolved in previous solution at 10 • C for 170, 640 s and 3 h, respectively. These control samples were referred to as TNAs60 series. All samples were post annealed in air at 450 • C for 2 h with a heating speed of 5 • C · min −1 . The annealed TNAs120 (80 s) samples were sequentially dipped in two different solutions for 3 min in each one. One is 0.1 M Cd(NO 3 ) 2 ethanol solution, and the other is 0.1 M Na 2 S methanol solution. The solution containers were put in a 300 W ultrasonic machine during dipping processes. The process was referred to as U-SILAR method. As to the traditional SILAR process, the TNAs120 (80 s) samples were sequentially dipped in the previous solutions without ultrasonic vibration for 5 min. A scanning electron microscope (SEM) Hitachi FE-SEM S4800 was employed for characterizing the morphology of the samples, and the compositional analysis was performed by energy dispersive X-ray spectrometer (EDS) attached to the SEM. The diffuse reflection abz E-mail: [email protected] sorption spectra (DRS) were measured by UV-Vis spectrophotometer (ShimadzuUV-265). The photoelectric response of the samples was recorded with an electrochemical workstation (CHI660E). A white light source was utilized as an excitation source (intensity: 150 mW cm −2 ). Results and Discussion −2 ) and the durations of the first two stages are longer than those of TNAs120. Then the current shows a quasi-steady trend in later time. Different current variations mean different growth processes and morphologies of the resulted samples. As shown by the insets i

Rapid Biodegradation of the Organophosphorus Insecticide Chlorpyrifos by Cupriavidus nantongensis X1T

Chlorpyrifos was one of the most widely used organophosphorus insecticides and the neurotoxicity and genotoxicity of chlorpyrifos to mammals, aquatic organisms and other non-target organisms have caused much public concern. Cupriavidus nantongensis X1T, a type of strain of the genus Cupriavidus, is capable of efficiently degrading 200 mg/L of chlorpyrifos within 48 h. This is ~100 fold faster than Enterobacter B-14, a well-studied chlorpyrifos-degrading bacterial strain. Strain X1T can tolerate high concentrations (500 mg/L) of chlorpyrifos over a wide range of temperatures (30–42 °C) and pH values (5–9). RT-qPCR analysis showed that the organophosphorus hydrolase (OpdB) in strain X1T was an inducible enzyme, and the crude enzyme isolated in vitro could still maintain 75% degradation activity. Strain X1T can simultaneously degrade chlorpyrifos and its main hydrolysate 3,5,6-trichloro-2-pyridinol. TCP could be further metabolized through stepwise oxidative dechlorination and further opening of the benzene ring to be completely degraded by the tricarboxylic acid cycle. The results provide a potential means for the remediation of chlorpyrifos- contaminated soil and water

Highly Efficient Adsorption Characteristics and Mechanism of Nutshell Biochars for Aromatic Organophosphorus Insecticides

The wide use of the insecticide profenofos in crop production has led to serious ecological water problems in agricultural fields. With the increasing global production of nuts, a large amount of nutshell waste has a serious impact on the environment. Turning nutshell waste into biochar to remove high levels of profenofos in water is a cost-effective treatment method. In this study, biochars made from nutshell waste are investigated for the adsorption of aromatic organophosphorus insecticide profenofos. The adsorption amount of nutshell biochar was 13-fold higher than crop stalk biochar in removing profenofos from water. The results indicated that the adsorption of profenofos by nutshell biochar was specific. Scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET) analysis showed that nutshell biochars had a larger specific surface area and more microporous structures. Meanwhile, nutshell biochars could exhibit a stable adsorption capacity at different initial concentrations of profenofos (10–40 mg/L), temperature (298–318 K), and pH (3–7). Desorption and reuse experiments showed that profenofos was firmly bound to nutshell biochars in water and could be extracted from the biochars with acetonitrile. Within 10 times of recycling, nutshell biochar had a stable and strong adsorption capacity for profenofos. The adsorption process of profenofos by nutshell biochar was pore diffusion and surface adsorption, which is consistent with the pseudo second-order kinetic model and the Freundlich isotherm model. Elemental and Fourier transform infrared spectroscopy (FTIR) analyses showed that the adsorption mechanism of profenofos on nutshell biochar was mainly through π-π and hydrophobic interactions. Nutshell biochar also showed strong adsorption capacity for other aromatic organophosphorus pesticides, and the adsorption rates of methyl parathion, isocarbophos and 2-chloro-4-bromophenol were 85%, 73% and 73%, respectively. Nutshell biochar can serve as an excellent material for removing aromatic organophosphorus insecticide pollution from water

Myricetin Inhibits Photodegradation of Profenofos in Water: Pathways and Mechanisms

Profenofos is a detectable insecticide in the environment with strong toxicity to non-targeted organisms. Photodegradation is a main transformation of profenofos in the environment. Myricetin is a flavonoid that strongly scavenges free radicals. The effect of myricetin on the photodegradation of profenofos was studied. The half-lives (T1/2) of profenofos were 1.7–7.0 and 90 h under artificial light and sunlight. The photolysis rate of profenofos decreased by 1.87–4.72 and 7.62 times with the addition of 20 ratios of myricetin. Free radicals reacting with profenofos were •OH and 1O2, and the key free radical was •OH. Myricetin strongly scavenged •OH and 1O2 which rapidly reacted with profenofos. O-(2-Chlorophenyl)-O-ethyl-S-propyl phosphorothioate (M3) and O-(2-chlorophenyl)-O-ethyl phosphorothioate (M4) were major and new photoproducts of profenofos. According to the Ecological Structure Activity Relationships, photodegradation of profenofos was a detoxification process, but myricetin inhibited the photodegradation of profenofos and its photoproducts. These results highlight the implication of myricetin on the fate and potential risk of profenofos in the environment

Quantitative Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry Method for Comparison of Prochloraz Residue on Garlic Sprouts after Soaking and Spraying Treatment

Prochloraz is a fungicide that is widely used on vegetables to maintain freshness during storage. To ensure that prochloraz is used in a safe way that reduces the levels of residue on the product, we evaluated two treatment methods (soaking and spraying) that are commonly used for garlic sprouts. An ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for prochloraz residue on garlic sprouts. The linear range of the method was 5–500 μg/kg and the correlation coefficient was 0.9983. The average recovery range was 88–94%, and the relative standard deviation range was 2.6–9.7%. Garlic sprout samples that had been soaked in or sprayed with prochloraz were collected from cold storage facilities in Laixi and Pingdu, China. For the soaked samples, the ranges for the levels of prochloraz residue on the whole garlic sprouts and stems (edible portion) were 15.76–25.14 mg/kg and 0.58–1.62 mg/kg, respectively. For the sprayed samples, the ranges for the levels of prochloraz residue on the whole garlic sprouts and stems were 1.85–7.89 mg/kg and 0.01–1.29 mg/kg, respectively. The results of this study provide a scientific basis for rationalizing the use of prochloraz and improving the safety of edible garlic sprouts

Residue Dynamics and Risk Assessment of Prochloraz and Its Metabolite 2,4,6-Trichlorophenol in Apple

The residue dynamics and risk assessment of prochloraz and its metabolite 2,4,6-trichlorophenol (2,4,6-TCP) in apple under different treatment concentrations were investigated using a GC-ECD method. The derivatization percent of prochloraz to 2,4,6-TCP was stable and complete. The recoveries of prochloraz and 2,4,6-TCP were 82.9%–114.4%, and the coefficients of variation (CV) were 0.7%–8.6% for the whole fruit, apple pulp, and apple peel samples. Under the application of 2 °C 2.0 g/L, 2 °C 1.0 g/L, 20 °C 2.0 g/L, and 20 °C 1.0 g/L treatment, the half-life for the degradation of prochloraz was 57.8–86.6 d in the whole fruit and apple peel, and the prochloraz concentration in the apple pulp increased gradually until a peak (0.72 mg·kg−1) was reached. The concentration of 2,4,6-TCP was below 0.1 mg·kg−1 in four treatment conditions and not detected (<LOD) in apple pulp. Finally, based on the detection of market samples in Hefei (China), we believe that the residual level of prochloraz in apples meets the requirements of the Chinese standards

A Simple and Effective Ratiometric Fluorescent Probe for the Selective Detection of Cysteine and Homocysteine in Aqueous Media

Biothiols such as cysteine (Cys) and homocysteine (Hcy) are essential biomolecules participating in molecular and physiological processes in an organism. However, their selective detection remains challenging. In this study, ethyl 2-(3-formyl-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (NL) was synthesized as a ratiometric fluorescent probe for the rapid and selective detection of Cys and Hcy over glutathione (GSH) and other amino acids. The fluorescence intensity of the probe in the presence of Cys/Hcy increased about 3-fold at a concentration of 20 equiv. of the probe, compared with that in the absence of these chemicals in aqueous media. The limits of detection of the fluorescent assay were 0.911 μM and 0.828 μM of Cys and Hcy, respectively. 1H-NMR and MS analyses indicated that an excited-state intramolecular proton transfer is the mechanism of fluorescence sensing. This ratiometric probe is structurally simple and highly selective. The results suggest that it has useful applications in analytical chemistry and diagnostics