Qijun Song

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.

Double Detection of Mycotoxins Based on SERS Labels Embedded Ag@Au Core–Shell Nanoparticles

A sensitive surface-enhanced Raman scattering (SERS) signal dependent double detection of mycotoxins is achieved for the first time, without the aid of nucleic acid amplification strategies. SERS labels embedded Ag@Au core-shell (CS) nanoparticles (NPs) as novel SERS tags are successfully prepared through a galvanic replacement-free deposition. SERS tags produce stable and quantitative SERS signal, emerging from the plasmonic coupling at the junction of Ag core and Au shell. SERS tags engineered Raman aptasensors are developed for the double detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1) in maize meal. The limits of detection (LODs) are as low as 0.006 ng/mL for OTA and 0.03 ng/mL for AFB1. The developed protocol can be extended to a large set of different SERS tags for the sensitive detection of multiple targets that possess different lengths of aptamers.

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.

Au nanoflower–Ag nanoparticle assembled SERS-active substrates for sensitive MC-LR detection

Surface-enhanced Raman scattering (SERS)-active substrates assembled by two types of metallic nanoparticles (NPs) were fabricated. Aptamers driven Au nanoflower (Au NF)-Ag NP core-satellite assemblies exhibited amplified SERS signals and achieved the sensitive detection of microcystin-LR (MC-LR) in Tai lake water with the limit of detection (LOD) of 8.6 ± 0.4 pM.

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.

Au NPs driven electrochemiluminescence aptasensors for sensitive detection of fumonisin B1

In this study, a simple gold nanoparticles (Au NPs) driven electrochemiluminescence (ECL) aptasensor was fabricated for the sensitive detection of fumonisin B1 (FB1), taking advantages of the weak background noise and good ECL efficiency of the ionic iridium (Ir) complex, the high affinity and specificity of aptamers for targets, and the large specific surface and excellent conductivity of Au NPs. Different amounts of Ir complex were loaded on the surface of Au NPs through mercaptoethylamine. The Au NP–Ir complex served as a nanoprobe and was applied in the development of an ECL-aptasensor, and a limit of detection (LOD) as low as 0.27 ng mL−1 was achieved for FB1. The proposed method not only has high sensitivity, but also showed good accuracy and stability. The principle proposed in this paper could be widely applicable in the development of nanomaterial-driven ECL-aptasensors for other mycotoxin detection.

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.

Tunable preparation of ruthenium nanoparticles with superior size-dependent catalytic hydrogenation properties

Ruthenium (Ru) featured with an unusual catalytic behavior is of great significance in several heterogeneous and electro-catalytic reactions. The preparation of tractable Ru nanocatalysts and the building of highly active catalytic system at ambient temperature remains a grand challenge. Herein, a facile strategy is developed for the controllable preparation of Ru nanoparticles (NPs) with the sizes ranging from 2.6 to 51.5nm. Ru NPs show superior size-dependent catalytic performance with the best kinetic rate constant as high as -1.52min-1, which could far surpass the other traditional noble metals. Ru NPs exert exceedingly efficient low-temperature catalytic activity and good recyclability in the catalytic reduction of nitroaromatic compounds (NACs) and azo dyes. The developed catalytic system provides a distinguishing insight for the artificial preparation of Ru NPs with desired sizes, and allows for the development of rational design rules for exploring catalysts with superior catalytic performances, potentially broadening the applications of metallic NP-enabled catalytic analysis.