Zhuqing Wang

Modifying Fe3O4 microspheres with rhodamine hydrazide for selective detection and removal of Hg2+ ion in water

Rhodamine hydrazide modifying Fe(3)O(4) microspheres (Fe(3)O(4)-R6G) was developed for selective detection and removal of mercury ion from water. With a saturation magnetization of 74.2 emu/g, the Fe(3)O(4)-R6G could be simply recollected from water with magnetic separation within a few minutes. The selectivity and adsorption ability of Fe(3)O(4)-R6G for metal cations were studied by fluorophotometry and atomic absorption spectrometry, respectively. The results showed that Fe(3)O(4)-R6G exhibited excellent selectivity for sensing mercury ion over other metal ions in aqueous solution, and also adsorbed 91% of mercury ion. The maximum adsorption capacity of the Fe(3)O(4)-R6G for Hg(2+) ion was 37.4 μmol g(-1). The Fe(3)O(4)-R6G was successfully applied to the determination of Hg(2+) in environmental samples, and could be used repeatedly by treatment with tetrabutylammonium hydroxide.

Colorimetric detection of copper and efficient removal of heavy metal ions from water by diamine-functionalized SBA-15

SBA-15 functionalized with N-[3-(trimethoxysilyl)propyl]ethylene-diamine (TPED) was synthesized and used for the colorimetric detection of Cu(2+) and removal of heavy metal ions in aqueous solutions. Compared to free SBA-15, the adsorption ability of diamine-functionalized SBA-15 (depicted as SBA-TPED) increased remarkably, the maximum adsorption capacity of SBA-TPED for Cu(2+), Pb(2+) and Zn(2+) was 27.22, 96.43 and 12.16 mg g(-1), respectively. Furthermore, SBA-TPED exhibits high selectivity for Cu(2+) with the relative selectivity coefficient of SBA-TPED for Cu(2+)/Pb(2+) being over 10 and for Cu(2+)/Zn(2+) being over 60. The naked-eye detection limit of SBA-TPED for Cu(2+) is 0.95 ppm, and the determination of Cu(2+) in real water samples also displays satisfactory results. Moreover, SBA-TPED possesses fast kinetics for removing Cu(2+) with a saturation time of less than 30 min, and can be regenerated by simple acid treatment.

A novel AgNPs-based colorimetric sensor for rapid detection of Cu2+ or Mn2+ via pH control

In this study, we propose a new silver nanoparticles (AgNPs)-based colorimetric sensor for rapid detection of Cu2+ or Mn2+ at pH 1.9 or 12.0, respectively. At pH 1.9, the AgNPs stabilized with sodium pyrophosphate (Na4P2O7) and hydroxypropylmethylcellulose (HPMC) gradually become smaller in the presence of Cu2+ resulting in a color change of the solution from yellow to colorless. At pH 12.0, however, the AgNPs aggregate immediately in the presence of Mn2+, which induces a color change of the solution from yellow to brown. The incubation time between the detection system and metal ion (Cu2+ or Mn2+) is fixed at 10 min. This mechanism is confirmed using UV-vis spectroscopy, Transmission electron microscopy (TEM), Dynamic light scattering (DLS) and Fourier-Transform Infrared Spectrometry (FT-IR). At the optimized experimental conditions, the selectivity of our AgNPs-based detection system is excellent for Cu2+ or Mn2+ compared with other metal ions. The limit of detections (LODs) of Cu2+ and Mn2+ by the naked eye are respectively 0.05 and 0.5 μM, and those by UV-vis spectroscopy are respectively 2.0 and 20 nM. The above LODs are all lower than the corresponding national drinking water standards (16 μM of Cu2+ and 1.8 μM of Mn2+). The applicability of our AgNPs-based colorimetric sensor is also validated by detection of Cu2+ and Mn2+ in tap water and lake water. Therefore, these results reinforce that our AgNPs-based colorimetric sensor is applicable to rapid colorimetric detection of Cu2+ and Mn2+ in complicated real water samples with excellent selectivity and high sensitivity.

Recent Advances in Nanoporous Membranes for Water Purification

Nanoporous materials exhibit wide applications in the fields of electrocatalysis, nanodevice fabrication, energy, and environmental science, as well as analytical science. In this review, we present a summary of recent studies on nanoporous membranes for water purification application. The types and fabrication strategies of various nanoporous membranes are first introduced, and then the fabricated nanoporous membranes for removing various water pollutants, such as salt, metallic ions, anions, nanoparticles, organic chemicals, and biological substrates, are demonstrated and discussed. This work will be valuable for readers to understand the design and fabrication of various nanoporous membranes, and their potential purification mechanisms towards different water pollutants. In addition, it will be helpful for developing new nanoporous materials for quick, economic, and high-performance water purification.

High-Performance Colorimetric Detection of Thiosulfate by Using Silver Nanoparticles for Smartphone-Based Analysis

Developing thiosulfate (S2O32-) sensors with silver nanoparticles (AgNPs) for analysis of aqueous solutions with the interference of other anions remains challenging. In this study, we propose a new strategy for excellent selective colorimetric detection of S2O32-. The nonmorphological transition of AgNPs leading to a color change from yellow to brown is verified by UV-vis, TEM, DLS, SEM, and XPS analyses. The sensor exhibits high sensitivity with detection limits of 1.0 μM by naked-eye determination and 0.2 μM by UV-vis spectroscopy analysis. The linear relationship (R2 = 0.998) between the (A0 - A)/A0 values and S2O32- concentrations from 0.2 μM to 2.0 μM indicates that the fabricated AgNPs-based colorimetric sensor can be employed for quantitative assay of S2O32-. Colorimetric responses are also monitored using the built-in camera of a smartphone. The sensor shows a linear response to S2O32- in 0-20.0 μM solutions under the optimized conditions and is thus more suitable for rapid on-site tests than other detection methods. A smartphone application (app) is downloaded under Android or IOS platforms to measure the RGB (red, green, blue) values of the colorimetric sensor after exposure to the analyte. Following data processing, the RGB values are converted into concentration values by using preloaded calibration curves. Confirmatory analysis indicates that the proposed S2O32- colorimetric sensor exhibits feasibility and sensitivity for S2O32- detection in real environmental samples.

Selective Extraction and Detection of Hg2+ in Aqueous Solution by using Rhodamine Dye-Modified Silica Gel

Novel silica gel-immobilized rhodamine (SGR) anchored by hydrazinium hydrate was synthesized. The selectivity and adsorption ability of the SGR for metal cations were investigated with fluorophotometry and atomic absorption spectrophotometery, respectively. The SGR exhibits high selectivity and adsorption capacity for Hg2+. The maximum static adsorption capacity of the SGR for Hg2+ was 25.8 μmol g−1. The linear response range covers a concentration range of Hg2+ from 20 ppb to 2000 ppb and the detection limit is 10 ppb. The determination of Hg2+ in real water samples displays satisfactory results, and the SGR can be used repeatedly by treating with a solution of tetrabutylammonium hydroxide.

A rapid colorimetric method for the detection of deltamethrin based on gold nanoparticles modified with 2-mercapto-6-nitrobenzothiazole

In this study, we developed a rapid colorimetric method for the detection of deltamethrin using gold nanoparticles modified with 2-mercapto-6-nitrobenzothiazole (Au NPs–MNBT): deltamethrin adhered onto the surface of Au NPs–MNBT and a core–shell structure formed with Au NPs–MNBT as the core and deltamethrin as the shell. The formation of the core–shell structure caused the change of solution color and UV-visible absorption spectra of Au NPs, which can be used to quantitatively detect deltamethrin by the naked eye and using a UV-Vis spectrophotometer. The effect of MNBT content, detection pH and reaction time on the detection of deltamethrin was studied in detail, and the selectivity and anti-interference ability of the probe were tested. The results showed that the probe can be used to detect deltamethrin rapidly and accurately from 13 kinds of other pesticides. The detection of deltamethrin was not affected when 5 times the concentration of other pesticides coexisted with deltamethrin. The detection limit of deltamethrin was observed to be 0.25 μM by the naked eye and 0.005 μM by UV-Vis spectroscopy. The extract solutions of small tomato and cherry were used to evaluate the feasibility of this detection method in actual samples and the results were consistent with that of gas chromatography-mass spectrometry, which proved that the developed method has actual sample application potential for deltamethrin detection.