Chan Wang

One step synthesis of fluorescent smart thermo-responsive copper clusters: a potential nanothermometer in living cells

Temperature measurement in biology and medical diagnostics, along with sensitive temperature probing in living cells, is of great importance; however, it still faces significant challenges. Metal nanoclusters (NCs) with attractive luminescent properties may be promising candidates to overcome such challenges. Here, a novel one-step synthetic method is presented to prepare highly fluorescent copper NCs (CuNCs) in ambient conditions by using glutathione (GSH) as both the reducing agent and the protective layer preventing the aggregation of the as-formed NCs. The resultant CuNCs, with an average diameter of 2.3 nm, contain 1–3 atoms and exhibit red fluorescence (λem = 610 nm) with high quantum yields (QYs, up to 5.0%). Interestingly, the fluorescence signal of the CuNCs is reversibly responsive to the environmental temperature in the range of 15–80 °C. Furthermore, as the CuNCs exhibit good biocompatibility, they can pervade the MC3T3-E1 cells and enable measurements over the physiological temperature range of 15–45 °C with the use of the confocal fluorescence imaging method. In view of the facile synthesis method and attractive fluorescence properties, the as-prepared CuNCs may be used as photoluminescence thermometers and biosensors.

Gold nanoclusters decorated with magnetic iron oxide nanoparticles for potential multimodal optical/magnetic resonance imaging

Efficient nanoprobes for fluorescent and magnetic resonance multimodal imaging (MRI/FI) are in high demand in bioimaging. Herein, a nanoprobe with fluorescent gold nanoclusters (NCs) and magnetic iron oxide composite materials (Fe3O4@AuNCs) was prepared for dual bioimaging. The AuNCs were synthesized using the glutathione (GSH) template. The hydrophobic Fe3O4 magnetic nanoparticles (MNPs) were capped with cetyltrimethyl ammonium bromide (CTAB) to obtain hydrophilic Fe3O4 MNPs. Subsequently, the Fe3O4@AuNCs were prepared by the adsorption of Fe3O4–CTAB on the GSH–AuNCs through electrostatic attraction. The resultant Fe3O4@AuNCs, having an average size of 13.5 nm, can be readily dispersed in water, which displayed a strong red fluorescence (λEm = 650 nm) with a quantum yield of 4.3%. Confocal laser scanning microscopy studies proved that the Fe3O4@AuNCs have good photostability and low cytotoxicity to 293T cells. The magnetic properties of Fe3O4@AuNCs showed that this material was a T2-based contrast agent for MRI with a transverse relaxivity r2 of 20.4 mM−1 S−1. Furthermore, the signal intensity of the T2-weighted MRI decreased with an increase in the concentration. The dual optical and magnetic properties of the synthesized Fe3O4@AuNCs were applicable to dual fluorescence and MR-based imaging.

Interfacial synthesis of polyethyleneimine-protected copper nanoclusters: Size-dependent tunable photoluminescence, pH sensor and bioimaging

The copper nanoclusters (CuNCs) offer excellent potential as functional biological probes due to their unique photoluminescence (PL) properties. Herein, CuNCs capped with hyperbranched polyethylenimine (PEI) were prepared by the interfacial etching approach. The resultant PEI-CuNCs exhibited good dispersion and strong fluorescence with high quantum yields (QYs, up to 7.5%), which would be endowed for bioimaging system. By changing the reaction temperatures from 25 to 150 °C, the size of PEI-CuNCs changed from 1.8 to 3.5 nm, and thus tunable PL were achieved, which was confirmed by transmission electron microscopy (TEM) imagings and PL spectra. Besides, PEI-CuNCs had smart absorption characteristics that the color changes from colorless to blue with changing the pH value from 2.0 to 13.2, and thus they could be used as color indicator for pH detection. In addition, the PEI-CuNCs exhibited good biocompatibility and low cytotoxicity to 293T cells through MTT assay. Owing to the positively charged of PEI-CuNCs surface, they had the ability to capture DNA, and the PEI-CuNCs/DNA complexes could get access to cells for efficient gene expression. Armed with these attractive properties, the synthesized PEI-CuNCs are quite promising in biological applications.

A fluorescent biosensor of lysozyme-stabilized copper nanoclusters for the selective detection of glucose

Glucose biosensors have attracted increased attention, as the rapid and sensitive detection of glucose is highly desirable for diabetes diagnosis. In this article, we designed a type of lysozyme functionalized fluorescence copper nanoclusters (Lys-CuNCs) to detect glucose levels in blood samples. Fluorescence measurements were carried out to optimize the synthesis conditions (e.g. mass ratio, pH and reaction time) for the biosensor. Under optimum conditions, the obtained Lys-CuNCs with an average diameter of 2 nm exhibited bright orangey-red fluorescence with high quantum yields (up to 5.6%). The fluorescence signal of Lys-CuNCs was quenched upon the addition of glucose, presumably due to the reduction of Cu(I) on the NCs surface by glucose. Thus the Lys-CuNCs can be served as a biosensor for glucose detection and two linear response ranges respectively in 0.03–10 μM and 0.5–10 mM of glucose were observed with a detection limit of 1.9 nM. Furthermore, this biosensor showed superior selectivity for various interferences, including light radiation, metal ions, carbohydrates and amino acids. In view of these properties, the Lys-CuNCs biosensor was applied in the determination of glucose in blood samples, and the results agreed well with that obtained from a currently used clinical method. Finally the visualized fluorescence variation of Lys-CuNCs may further enable the rapid and simple detection of glucose level in blood.

Bi-functional fluorescent polymer dots: a one-step synthesis via controlled hydrothermal treatment and application as probes for the detection of temperature and Fe3+

A one-step controlled hydrothermal method was described to prepare highly fluorescent polymer dots (PDs) by using polyethylene glycol as the carbon source. The synthesized PDs with an average diameter of 2.5 nm exhibit strong blue fluorescence with high quantum yields (QYs, up to 19%). Further modification of these PDs with glutathione (GSH) endows the resultant GSH–PDs with bi-functional fluorescence responses to temperature and Fe3+. Interestingly, the fluorescence signal of the GSH–PDs is reversibly responsive to the environmental temperature in the range of 20–75 °C. As the GSH–PDs exhibit good biocompatibility, they can pervade the MC3T3-E1 cells and enable the measurement of temperature over the physiological range of 20–45 °C using the confocal fluorescence imaging method. The GSH–PDs were also explored as a fluorescent probe for Fe3+ ion detection, and the linear response range in 0.1–10 μM was observed with a detection limit of 3.7 nM. Thus, the bi-functional measurement of temperature and Fe3+ ions was achieved by the fluorescent PD chemosensor.

Controlled growth of MoS2 nanopetals and their hydrogen evolution performance

Edge-oriented MoS2 nanopetals complexed with basal-oriented MoS2 thin films have been mildly grown through a simple atmospheric pressure chemical vapor deposition (APCVD) process with the reaction of MoO3 and S. Dense nanopetals with hexagonal structures exposed numerous chemically reactive edge sites. The roles of growth temperature, time and S/MoO3 mass ratio have been carefully investigated to tune the morphology and density of the as-grown products. Importantly, the carbon nanotube (CNT) films were used as substrates for growing MoS2 nanopetals. The MoS2/CNT composites, used directly as working electrodes, showed remarkable and stable electrocatalytic activity in the hydrogen evolution reaction (HER), as manifested with a low onset overpotential of ∼100 mV and a small Tafel slope of 49.5 mV per decade. The development of the MoS2/CNT electrode provides a promising way to fabricate other multifunctional electrodes.

Rational Design of Magnetic Micro-nanoelectrodes for Recognition and Ultrasensitive Quantification of Cysteine Enantiomers

Driven by the urgent need for recognition and quantification of trace amino acids enantiomers in various biologic samples, we demonstrate for the first time an ultrasensitive electrochemical chiral biosensor for cysteine (Cys) based on magnetic nanoparticles (Fe3O4@PDA/Cu xO) as electrode units. d-Cys-Cu2+-d-Cys formed in the presence of cysteine exhibits strong stability and a shielding effect on the redox current of indicator Cu2+, which can be used to quantify and recognize d-Cys by square wave voltammetry. Simultaneous detection of d-Cys and homocysteine (Hcy) is achieved in the presence of other amino acids, demonstrating an excellent selectivity of the sensor. Moreover, aided by the enrichment treatment effect of magnetic micronanoelectrodes, an ultrahigh sensitivity up to 102 μA μM-1 cm-2 was achieved, the detection limit is reduced to picomolar level (83 pM) for d-Cys and can be used for the recognition of cysteine enantiomers. The proposed method has been verified by real sample analysis with satisfactory results. The results highlight the feasibility of our proposed strategy for magnetic micronanoelectrode sensor, electrochemical recognition, and quantification of d-Cys, which can be more broadly applicable than that with traditional electrode structures and further advance the field of electrochemical sensors.

Novel tungsten phosphide embedded nitrogen-doped carbon nanotubes: A portable and renewable monitoring platform for anticancer drug in whole blood

Biosensors based on converting the concentration of analytes in complex samples into single electrochemical signals are attractive candidates as low cost, high-throughput, portable and renewable sensor platforms. Here, we describe a simple but practical analytical device for sensing an anticancer drug in whole blood, using the detection of methotrexate (MTX) as a model system. In this biosensor, a novel carbon-based composite, tungsten phosphide embedded nitrogen-doped carbon nanotubes (WP/N-CNT), was fixed to the electrode surface that supported redox cycling. The electronic transmission channel in nitrogen doped carbon nanotubes (N-CNT) and the synergistic effect of uniform distribution tungsten phosphide (WP) ensured that the electrode materials have outstanding electrical conductivity and catalytic performance. Meanwhile, the surface electronic structure also endows its surprisingly reproducible performance. To demonstrate portable operation for MTX sensing, screen printing electrodes (SPE) was modified with WP/N-CNT. The sensor exhibited low detection limits (45 nM), wide detection range (0.01-540 μM), good selectivity and long-term stability for the determination of MTX. In addition, the technique was successfully applied for the determination of MTX in whole blood.

A highly active K/Cu-Mn-O catalyst for the removal of nitric oxide in indoor air:

Nitric oxide is a frequently encountered pollutant in indoor air. It could have a number of harmful effects on human health even at low concentration. Aiming to improve the indoor air quality, an environment-friendly method was developed for the elimination of nitric oxide at ppm level based on a low temperature effective catalyst potassium-doped copper–manganese oxide (K/Cu-Mn-O). The catalyst was obtained through a co-precipitation method using metal nitrates in aqueous solution and the precipitate was calcinated at 400℃ for 5 h. After impregnation with K, the best catalytic activity was observed for the K/Cu-Mn-O catalyst with a Cu/Mn ratio of 1:2 and surface concentration of doping K 7.03% (7.4 mg/g). The composition and the structure of the catalyst were comprehensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller. The results showed that the potassium doping improved the adsorption ability of catalyst, and promoted the formation of the nitrate salt, and thereby further improved the elimination rate of nitric oxide. Finally, the possible reaction mechanisms are discussed.