Ming Xuan Gao

Porous hollow CuS nanospheres with prominent peroxidase-like activity prepared in large scale by a one-pot controllable hydrothermal step

CuS materials with peroxidase activity have been prepared but greatly limited by the large dosage and low peroxidase activity. In this paper, porous hollow CuS nanospheres with a variety of sizes were fabricated by one-pot method based on a facile template-assisted hydrothermal approach. The size of the porous hollow CuS nanospheres could be simply tuned by adjusting the molar ratios of reactants, the reaction temperature, and time. The as-prepared porous hollow CuS nanospheres were demonstrated to exhibit more prominent intrinsic peroxidase-like activity using TMB as a peroxidase substrate in the presence of hydrogen peroxide (H2O2). This is a significant comparison to previous reports, demonstrating that the new developed synthetic porous hollow CuS nanospheres can be a new kind of candidate for peroxidase mimics, and the nanospheres are promising for applications in biosensors, environmental monitoring, and so on.

Efficient visible-light photocatalytic heterojunctions formed by coupling plasmonic Cu2−xSe and graphitic carbon nitride

Photocatalytic semiconductors have attracted considerable attention due to their applications in the degradation of organic pollutants. However, the low solar-light harvesting and high electron–hole recombination rate limit the efficiency of photocatalysts. The newly developed localized surface plasmon resonance (LSPR) can offer a new opportunity to overcome the limited efficiency to some extent. In this study, heterojunctions (Cu2−xSe–g-C3N4) incorporating plasmonic semiconductor Cu2−xSe with graphitic carbon nitride (g-C3N4) are proposed as visible light photocatalysts. Their photocatalytic performance is tested and proven via the degradation of methyl blue (MB) in an aqueous solution. When the mass percentage composition of Cu2−xSe reached 60%, the as-prepared composite exhibited the highest photocatalytic activity, which was almost 6.1 and 2.8 times as high as that of individual Cu2−xSe and g-C3N4, respectively. The remarkable photocatalytic efficiency of such Cu2−xSe–g-C3N4 heterojunctions under visible light illumination due to both plasmonic enhancement of the catalyst and synergetic effect of the co-catalyst is shown. This work can provide a new methodology to develop stable and highly efficient heterojunction photocatalysts.

Visual Identification of Light-Driven Breakage of the Silver-Dithiocarbamate Bond by Single Plasmonic Nanoprobes

Insight into the nature of metal-sulfur bond, a meaningful one in life science, interface chemistry and organometallic chemistry, is interesting but challenging. By utilizing the localized surface plasmon resonance properties of silver nanoparticles, herein we visually identified the photosensitivity of silver-dithiocarbamate (Ag-DTC) bond by using dark field microscopic imaging (iDFM) technique at single nanoparticle level. It was found that the breakage of Ag-DTC bond could be accelerated effectively by light irradiation, followed by a pH-dependent horizontal or vertical degradation of the DTC molecules, in which an indispensable preoxidation process of the silver was at first disclosed. These findings suggest a visualization strategy at single plasmonic nanoparticle level which can be excellently applied to explore new stimulus-triggered reactions, and might also open a new way to understand traditional organic reaction mechanisms.

Insight into a reversible energy transfer system

Resonance energy transfer (RET) processes have wide applications; these processes involve a unidirectional energy transfer from a particular donor to a particular acceptor. Here, we report a plasmonic resonance energy transfer (PRET), which occurs from the surface of gold nanoparticles to fluorescent organic dyes, and coexists with a nanometal surface energy transfer (NSET) that operates in the reverse direction. The coexistence of both PRET and NSET in opposite directions means that the roles of both donor and acceptor can be interchanged, which could be identified by using spectrofluorometric measurements and light scattering dark field microscopic imaging. The experimental data could be further theoretically supported using Persson and Langs model, the quasi-static approximation and finite-difference time-domain simulation. Moreover, disruption of the PRET process by altering the energy transfer pairs suggests that interactions occur inside the reversible energy transfer system, which manifest by increasing the fluorescence quenching efficiency of the NSET process.

Vertically aligned gold nanomushrooms on graphene oxide sheets as multifunctional nanocomposites with enhanced catalytic, photothermal and SERS properties

A novel and simple strategy for preparing vertically aligned gold nanomushrooms (AuNMs) on graphene oxide (GO) has been developed. The as-prepared GO/AuNM nanocomposites have been successfully applied in the catalytical organic transformation, photothermal ablation of bacteria and SERS detection.

General Sensitive Detecting Strategy of Ions through Plasmonic Resonance Energy Transfer from Gold Nanoparticles to Rhodamine Spirolactam

Plasmonic resonance energy transfer (PRET), which occurs between the plasmonic nanoparticles and organic dyes, has significant potential in target sensing chemistry owing to its sensitivity at the single nanoparticle level. In this contribution, by using AuNPs, which has localized surface plasmonic resonance light scattering (LSPR-LS) around 550 nm, as the donor of PRET, a general sensitive detecting strategy of ions were developed. Targets can specifically react with a ring-close structured rhodamine spirolactam, which was prepared from rhodamines in the presence of different primary amine wherein the option of the primary amine is up to the targets, forming ring-open structured rhodamine spirolactam with the strong absorption around 550 nm. This process triggered the PRET from gold nanoparticles (AuNPs) to the ring-open structured rhodamine spirolactam. As a proof of concept, Cu2+ and Hg2+ were detected by using rhodamine B hydrazide and N-(rhodamine B)lactam-ethylenediamine, respectively. With the aid of a dark field microscope, the LSPR-LS of AuNPs gets decreased within 10 min with the addition of Cu2+ or Hg2+. The scattering light spectra get red-shifted during the targets addition due to the quenching dip phenomenon. Further theoretical simulation indicated the PRET process could be aroused by the electric field diminishment of AuNPs via the interaction of rhodamine. This single nanoparticle based detecting strategy could be further applied for other anions, cations, or small organic molecules detection by simply changing the rhodamine spirolactam.

Plasmonic Cu2–xSySe1–y Nanoparticles Catalyzed Click Chemistry Reaction for SERS Immunoassay of Cancer Biomarker

Nature enzyme-based immunoassays have been widely used in fundamental scientific research and clinical diagnosis. However, the limitations of natural enzyme, such as the low physical/chemical stability or susceptibility to protein denaturation, greatly restrained its applications. In this article, we reported a new enzyme-free SERS immunoassay by utilizing plasmonic Cu2- xS ySe1- y nanoparticles (NPs) as nanocatalyst to catalyze the click chemistry between the azido and alkynyl substrate which is used as the SERS signal reporter. The unique vibration of C≡C of alkynyl in the Raman-silent region (1800-2800 cm-1) is not overlapped with the signals of the other conventional Raman reporters or endogenous biological species, and thus it can make sure the enzyme-free SERS immunoassay has high selectivity and sensitivity. As a proof of concept, prostate-specific antigen (PSA), a biomarker of prostate cancer in blood, has been detected. The SERS immunoassay shows good analytical performance for PSA in the range of 3-120 ng mL-1, and it has been successfully applied to detect PSA in the serum samples of prostate cancer patients, proving that the proposed enzyme-free SERS immunoassay has great potential in the clinical diagnosis of cancer.