Latest ArticlesAs an important component of the atmosphere, ammonia (NH3) plays a very important role in maintaining the balance of environment. However, it is also one of the most toxic gases that can cause damage to the human respiratory system and mucous membranes even at low concentrations. As such, development of highly sensitive and selective NH3 sensors is of high significance for environmental monitoring and health maintenance. Herein, we have synthesized Au@Ag@AgCl core-shell nanoparticles (NPs) by oxidative etching and precipitating Au@Ag core-shell NPs using FeCl3 and further used them as optical probes for the colorimetric detection of NH3. The sensing mechanism is based on the fact that the etching of NH3 on AgCl and Ag shell leads to the variations of ingredients and core-to-shell ratio of the Au@Ag@AgCl NPs, thereby inducing noticeable spectral and color changes. By replacing the outmost layer of Ag with AgCl, not only is the stability of the sensor against oxygen significantly enhanced, but also is the sensitivity of the method improved. The method exhibits good linear relationship for the detection of NH3 from 0 to 5000 μmol/L with the limit of detection of 6.4 μmol/L. This method was successfully applied to the detection of simulated air polluted by NH3, indicating its practical applicability for environmental monitoring. This method shows great potential for on-site NH3 detection particularly in remote area, where a simple, fast, low-cost, and easy-to-handle method is highly desirable.
Zero-dimensional carbon dots have emerged as important nanofillers for the separation membrane due to their small specific size and rich surface functional groups. This study proposed a strategy based on hydrophobic carbon dots (HCDs) to regulate water channels for an efficient forward osmosis (FO) membrane. Thin-film composite (TFC) membranes with superior FO performance are fabricated by introducing HCDs as the nanofiller in the polyacrylonitrile support layer. The introduction of HCDs promotes the formation of the support layer with coherent finger-like hierarchical channels and micro-convex structure and an integrated polyamide active layer. Compared to the original membrane, TFC-FO membrane with 10 wt% HCDs exhibits high water flux (15.47 L m−2h−1) and low reverse salt flux (2.9 g m−2h−1) using 1 mol/L NaCl as the draw solution. This improved FO performance is attributed to the lower structural parameters of HCDs-induced water channels and alleviated internal concentration polarization. Thus, this paper provides a feasible strategy to design the membrane structure and boost FO performance.
The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment. In this study, amorphous molybdenum sulfide composites (EDTA-MoSx (x=2, 3)) were fabricated via a facile hydrothermal method mediated by EDTA, which was applied to heavy metal ions (Cu2+, Cd2+, Pb2+, Zn2+ and Ni2+) removal from aqueous solutions. A case study for Cu2+ ions showed that the adsorption capacity of EDTA-MoSx (x=2, 3) was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L. Adsorption mechanisms of different sulfide groups and －COOH of EDTA-MoSx (x=2, 3) were verified systematically via a series of experiments, characterizations, and density functional theory (DFT) calculations. Both bridging S22− and －COOH covalently bonded with Cu2+ ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx (x=2, 3). This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.
A novel carbon-rich g-C3N4 nanosheets with large surface area was prepared by facile thermal polymerization method using urea and 1, 3, 5-cyclohexanetriol. Plenty of carbon-rich functional groups were introduced into the surface layers of g-C3N4, which constructed the built-in electric field (BIEF) and resulted in improved charge separation; therefore, the carbon-rich g-C3N4 displayed superior photocatalytic activity for amoxicillin degradation under solar light. The contaminant degradation mechanism was proposed based on radical quenching experiments, intermediates analysis and density functional theory (DFT) calculation. Moreover, the reusing experiments showed the high stability of the material, and the amoxicillin degradation under various water matrix parameters indicated its high applicability on pollutants treatment, all of which demonstrated its high engineering application potentials.
In this work, a novel blue-green fluorescence phosphorous oxide quantum dots (PO QDs) was synthesized by solvothermal method in N-methyl-2-pyrrolidone (NMP) solution without any protection treatment during synthesis. Upon excitation at 400 nm, PO QDs emitted blue-green fluorescence with quantum yield of 0.28. PO QDs exhibited the high inertness to air or moisture, the excellent water solubility, and stable emission intensity in a wide pH range and in high ionic strength solution. Interestingly, PO QDs could give the positive optical response to iron ions (Fe3+) and iodine ion (I−). The photoluminescence (PL) of PO QDs could be directly quenched by Fe3+. While I− quenched the PO QDs PL by means of Ag+-mediated PO QDs system via the internal filtration effects (IFE) induced by the formation of AgI. Moreover, the biocompatibility and low toxicity of PO QDs verified in bean sprout and Hela cells indicated the promising application of PO QDs in medicine related fields. Furthermore, PO QDs could also be utilized in luminescent composite film for various application scenarios
Ion-in-conjugation (IIC) materials are emerging as an important class of organic electronic materials with wide applications in energy storage, resistive memories and gas sensors. Many IIC materials were designed and investigated, however the role of conjugation in IIC materials' performance is yet investigated. Here we designed two molecules obtained by condensation of 4-butylaniline and oxocarbon acid. Squaric acid derivatives squaraine named SA-Bu and a croconamide named CA-Bu which only differ in their oxocarbon cores. While employing SA-Bu and CA-Bu as resistive memory and gas sensory materials, SA-Bu has attained promising performance in ternary memory and detection of NO2 as low as 10 parts-per-billion whereas CA-Bu show mainly binary memory behavior and negligible NO2 response. Theoretical calculations reveal that conjugation of CA-Bu was distorted by the increased steric hindrance, frustrating the charge transport and suppressing the conductivity. Our work demonstrates that the conjugation plays a crucial role in ion-in-materials promoting ternary RRAM devices and high-performance gas sensors manufacture.
Recently, the degradation of organic compounds in saline dye wastewater by sulfate radicals (SO4·-)-based advanced oxidation processes (AOPs) have attracted much attention. However, previous studies on these systems have selected non-chlorinated dyes as model compounds, and little is known about the transformation of chlorinated dyes in such systems. In this study, acid yellow 17 (AY-17) was selected as a model of chlorinated contaminants, and the degradation kinetics and evolution of oxidation byproducts were investigated in the UV/PDS system. AY-17 can be efficiently degraded (over 98% decolorization) under 90 min irradiation at pH 2.0–3.0, and the reaction follows pseudo-first order kinetics. Cl- accelerated the degradation of AY-17, but simultaneously led to an undesirable increase of absorbable organic halogen (AOX). Several chlorinated byproducts were identified by liquid chromatography-mass spectrometry (LC–MS/MS) in the UV/PDS system. It indicates that endogenic chlorine and exogenic Cl– reacted with SO4·- to form chloride radicals, which are involved in the dechlorination and rechlorination of AY-17 and intermediates. The possible degradation mechanisms of AY-17 photooxidative degradation are proposed. This work provides valuable information for further studies on the role of exogenic chloride in the degradation of chlorinated azo dyes and the kinetic parameters in the PDS-based oxidation process.
An intramolecular selenocyclizations of olefins mediated by a commercially available hypervalent iodine(III) reagent, PhIO, was developed. This method provided access to a wide range of selenenylated heterocycles under ambient conditions. The striking advantages of this protocol over all previous methods include mild reaction conditions, easy operation, good yields, high levels of functional group compatibility, large–scale application and suitability for the late-stage functionalization of complex molecules of biological importance.
Here we propose a fluorescent sensor, Chroma-V, consisted of a Hoechst ligand (Hoe) to target chromatin DNA and a BODIPY rotor (BDP) to sense the local viscosity that reflects chromatin condensation state. Within Chroma-V, efficient FRET process from Hoe to BDP facilitated a single-excitation ratiometric imaging of nucleus DNA under fluorescence confocal microscope, which utilized the ratio of two channels to enable an intuitive visualization of chromatin condensation state. And fluorescence lifetime imaging (FLIM) based on fluorescent signal from BDP proved to be a more accurate method to quantify the changes of chromatin condensation state under different epigenetic states, including histone acetylation regulated by deacetylase inhibitors, cell apoptosis induced by DNA-bining drugs, and the epithelial-mesenchymal transition of HUVEC cells induced by TGF-β.
Hydrogen sulfide (H2S) is a signaling molecule that plays important roles in biological systems. The exploration of H2S as a new drug release trigger and its related fluorescent theranostic system is crucial for cancer bio-imaging and therapy. Herein, we designed a new two-photon ratiometric fluorescent theranostic prodrug (compound 1) and studied its spectroscopic properties and application in in vivo imaging. Compound 1 specifically reacted with H2S and released the free active therapeutic component of 7-ethyl-10-hydroxycamptothecin, which was accompanied with a red-shift fluorescence emission signal from 460 nm to 545 nm. The exogenous and endogenous H2S in living cells were imaged by compound 1 under one-photon and two-photon excitation. Furthermore, compound 1 monitored the H2S concentration changes in Caenorhabditis elegans by fluorescence imaging. Additionally, it showed effective drug release activation in situ tumor with exogenous and endogenous H2S as the trigger. The H2S-sensitive activation and drug-release properties highlight the potential of theranostic compound 1 in future cancer treatment and therapy.
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