Metal Complex/ZnS-Modified Ni Foam as Magnetically Stirrable Photocatalysts: Roles of Redox Mediators and Carrier Dynamics Monitored by Operando Synchrotron X-ray Spectroscopy.

Magnetically stirrable photocatalysts binding the ZnS-decorated Ni foam with the metal complex cocatalyst as a redox mediator and light-absorbing composition were investigated. Loading metal complex can improve light absorption, surface hydrophilicity, interfacial charge migration, and H2 production activity. The variation of the metal valences of the composite photocatalysts in an operando environment (with sacrificial agent solution) with and without light irradiation was investigated by X-ray absorption near-edge structure (XANES) spectra and Fourier-transformed extended X-ray absorption fine structure (EXAFS) spectra to monitor the charge carrier dynamics of photocatalysis and explain how the macrocyclic Cu complex (CuC) acted as a redox mediator better than the Ni complex. The smaller valence difference of copper valence in ZS/CuC for dark and light states revealed that the Cu complex facilitates a reversible electron transfer between the ZnS photocatalyst and H+. Loading the Cu complex can improve the separation of photogenerated carriers by the redox couple of complexes, leading to a significantly improved photocatalytic H2 production activity of 8150 µmol h-1 g-1. The reactants can flow through these magnetically stirrable Ni foam-based photocatalysts by magnetic-field-driven stirring, which improves the contact between photocatalysts and the sacrificial agents. The operando synchrotron provides new insights for understanding the roles of redox mediators.

Recent Advances in Synthesis, Modification, Characterization, and Applications of Carbon Dots.

Although there is significant progress in the research of carbon dots (CDs), some challenges such as difficulty in large-scale synthesis, complicated purification, low quantum yield, ambiguity in structure-property correlation, electronic structures, and photophysics are still major obstacles that hinder the commercial use of CDs. Recent advances in synthesis, modification, characterization, and applications of CDs are summarized in this review. We illustrate some examples to correlate process parameters, structures, compositions, properties, and performances of CDs-based materials. The advances in the synthesis approach, purification methods, and modification/doping methods for the synthesis of CDs are also presented. Moreover, some examples of the kilogram-scale fabrication of CDs are given. The properties and performance of CDs can be tuned by some synthesis parameters, such as the incubation time and precursor ratio, the laser pulse width, and the average molar mass of the polymeric precursor. Surface passivation also has a significant influence on the particle sizes of CDs. Moreover, some factors affect the properties and performance of CDs, such as the polarity-sensitive fluorescence effect and concentration-dependent multicolor luminescence, together with the size and surface states of CDs. The synchrotron near-edge X-ray absorption fine structure (NEXAFS) test has been proved to be a useful tool to explore the correlation among structural features, photophysics, and emission performance of CDs. Recent advances of CDs in bioimaging, sensing, therapy, energy, fertilizer, separation, security authentication, food packing, flame retardant, and co-catalyst for environmental remediation applications were reviewed in this article. Furthermore, the roles of CDs, doped CDs, and their composites in these applications were also demonstrated.

A dimedone-phenylalanine-based fluorescent sensor for the detection of iron (III), copper (II), L-cysteine, and L-tryptophan in solution and pharmaceutical samples.

The development of fluorescence molecules for the fast and effective detection of L-tryptophan (L-Trp) has attracted a lot of attention because it is an important amino acid for baby growth, nitrogen equilibrium in adults, improving sleep, and mood regulation. A dimedone-phenylalanine-based chiral sensor (SDPA) was synthesized and exhibited a strong fluorescence quenching by Fe3+ and Cu2+ in a water/DMSO (3/7) solution with a detection limit of 2.29 × 10-6 M and 6.37 × 10-6 M, respectively. The factors affecting fluorescence sensings, such as the pH and competing cations, were studied. The sensor can be reused at least five times after being treated with EDTA. The Job plot, ESI-MS spectra, 1H NMR spectra, absorbance, and fluorescence titration experiments were investigated to study the mechanism of SDPA-Fe3+ and SDPA-Cu2+ complexation. The SDPA-Cu2+ complex can detect L-tryptophan and L-cysteine at trace levels by turn-on fluorescence with a detection limit of 9.35 × 10-6 M and 8.86 × 10-6 M, respectively. Moreover, applying the SDPA-Cu2+ complex for quantitative analysis of L-tryptophan in real sleep-improving capsules resulted in good recovery. The L-tryptophan level of the Elining capsule was determined at 190.8 ± 10.5 mg/g (mg L-tryptophan/g medicine), which is close to the announced quantity of 180 mg/g. Besides, the SDPA-Cu2+ complex can selectively detect free L-Try molecules and L-Try residues in proteins.

Naked-eye colorimetric and turn-on fluorescent Schiff base sensor for cyanide and aluminum (III) detection in food samples and cell imaging applications.

A new efficient Schiff base sensor SB3 for fluorescent and colorimetric "naked-eye" "turn-on" sensing of cyanide anion (CN-) with excellent sensitivity and selectivity was developed. The 4,4'-(perfluoropropane-2,2-diyl)bisphenol group and two phenyl groups were covalently linked by two C = N bonds to extend the conjugation length. The four hydroxyl groups can improve the water solubility of the SB3 sensor. The SB3 sensor exhibited high specificity towards CN- by interrupting its intramolecular charge transfer, resulting in a color change and remarkable "turn-on" green fluorescence emission. The sensing mechanism is caused by the nucleophilic addition of CN- toward imine groups of the SB3 sensor, leading to breaks of the conjugation, fluorescent spectral changes, and color change. It was confirmed by 1H NMR titration and Mass spectra. The detection limits for CN- and Al3+obtained by fluorescence spectrum are 0.80 µM and 0.25 µM, respectively. The SB3 sensor can act as an efficient chemical sensor for detecting the CN- and Al3+ ions under common environmental and physiological conditions (pH 5-12). Besides, the sensor can also detect CN- in food materials (such as sprouting potatoes and cassava flour) and imaging CN-in living cells with strong "turn-on" fluorescence at 490 nm. SB3 is an excellent CN- sensor that exhibits some advantages, including easy synthesis, distinct fluorescence and color change, high selectivity, low detection limit, and good anti-interference ability to analyze solution and food samples, together with fluorescence cell imaging.

Novel semi-automated graphene nanosheets based pipette-tip assisted micro-solid phase extraction as eco-friendly technique for the rapid detection of emerging environmental pollutant in waters.

In this work, a new semi-automated syringe infusion-pump assisted graphene nanosheets (GNSs) based pipette-tip micro-solid phase extraction (PT-µSPE) as a green sample preparation technique was demonstrated for the sensitive analysis of emerging environmental pollutant in environmental waters using HPLC-UV. Microwave-assisted synthesized GNSs powder was packed into a 100 µL pipette-tip (as PT-µSPE cartridge) connected with a commercial plastic syringe (contains water sample). This setup was attached to a programmable auto-syringe infusion pump for the GNSs-PT-µSPE process. Triclosan (TCS) is an emerging environmental pollutant chosen as a target analyte to examine the extraction capacity and feasibility of GNSs as a sorbent material for PT-µSPE. Parameters affecting the extraction capability were systematically evaluated and thoroughly optimized. At optimized experimental parameters, excellent linearity (r2 = 0.9979) was achieved over the concentration range of 2-250 ng mL-1 for TCS, with a detection limit of 0.5 ng mL-1. Applicability of the presented method was examined with real water samples, and extraction recoveries obtained were ranged between 94.6-102.4% with RSD less than 7.8%. The presented protocol is a simple, semi-automated, eco-friendly, low-cost, and efficient sample pretreatment technique for quick analysis of TCS in environmental wastewaters.

An aniline trimer-based multifunctional sensor for colorimetric Fe3+, Cu2+ and Ag+ detection, and its complex for fluorescent sensing of L-tryptophan.

The detection of metal ions and amino acids by the aniline oligomer-based receptor has not been reported yet, to the best of our knowledge. In this study, an efficient multifunctional cation-amino acid sensor (CAS) with aniline moiety and chiral thiourea binding site was synthesized by the reaction of aniline trimer and (S)-(+)-1-phenyl ethyl isothiocyanate. CAS can sense Fe3+, Cu2+, Ag+ ions, and L-tryptophan. These results can be recognized by the naked eye. The appropriate pH range for the quantitative analysis of Fe3+, Cu2+, and Ag+ by CAS in DMSO/water (30 vol% water) was evaluated. The interaction between CCS and metal ions was analyzed by 1H NMR titration. The detection limits of CAS for the Cu2+, Ag+, and Fe3+ were 0.214, 0.099, and 0.147 µM, respectively. Moreover, the CASCu2+ complex can act as a turn-on fluorescence sensor for L-tryptophan. On the contrary, there is no response upon the addition of other amino acids, such as L-histidine, L-proline, L-phenylalanine, L-threonine, L-methionine, L-tyrosine, and L-cystine to CASCu2+ complex.