Hong Yan Zou

Cu(I)-Doped carbon quantum dots with zigzag edge structures for highly efficient catalysis of azide–alkyne cycloadditions

Photoluminescent (PL) carbon quantum dots (CQDs), in which Cu(I) was doped stably owing to their specific zigzag edge structure, were used for catalyzing the Huisgen 1,3-dipolar cycloaddition between azides and alkynes, the prototypical reaction of “click chemistry”. The results showed the great potential of the as-prepared CQDs in catalysis chemistry applications.

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.

Synergetic Catalytic Effect of Cu2–xSe Nanoparticles and Reduced Graphene Oxide Coembedded in Electrospun Nanofibers for the Reduction of a Typical Refractory Organic Compound

A new heterogeneous catalytic composite composed of nonstoichiometric Cu2-xSe nanoparticles (NPs) with high copper deficiency and graphene oxide (GO) is prepared by coembedding in electrospun nanofibers of a poly(vinylpyrrolidone) (PVP) support, wherein GO in the nanofibers is converted into reduced GO (rGO) via heat treatment. The as-prepared composite Cu2-xSe/rGO/PVP nanofibers have demonstrated superior catalytic activity toward the reduction of a refractory organic compound by taking 4-nitrophenol (4-NP) as an example. In the presence of NaBH4, the Cu2-xSe/rGO/PVP nanofibers display a synergetic effect between Cu2-xSe and rGO in PVP nanofibers compared to their independent components or corresponding nanofibers. Furthermore, the Cu2-xSe/rGO/PVP nanofibers exhibit a favorable water-stable property via heat treatment to solidify the hydrophilic PVP matrix, which makes the composite display good reusability, stability in aqueous solution, and separability from a water medium. This work not only presents a direct, convenient, and effective approach to doping semiconductor nanomaterials into polymer nanofibers but also provides fundamental routes for further investigations about the synergetic effect between different materials based on the platform of electrospun nanofibers.

Sensitive and selective turn off-on fluorescence detection of heparin based on the energy transfer platform using the BSA-stabilized Au nanoclusters/amino-functionalized graphene oxide hybrids

An ultra-sensitive and selective turn off-on fluorescence detection of heparin based on the energy transfer in the BSA-stabilized gold nanoclusters/amino-functionalized graphene oxide (BSA-AuNCs/NH2-GO) hybrids was successfully realized. The BSA-AuNCs containing amounts of carboxyl groups could be absorbed on the surface of NH2-GO through the electrostatic interaction, which resulted in the fluorescence quenching of BSA-AuNCs with high efficiency. However, heparin, possessing high density of negative charge, could compete with BSA-AuNCs to bind NH2-GO and block the energy transfer from BSA-AuNCs to NH2-GO. The fluorescence recovery of BSA-AuNCs was closely related to the amount of heparin and there was a good linear relationship between fluorescence recovery of BSA-AuNCs and heparin over the range of 100ng/mL to 30μg/mL with a detection limit of 40ng/mL. Whats more, the fluorescence assay was successfully applied for heparin sensing in human serums and intracellular imaging.

Nonstoichiometric Cu2−xSe nanocrystals in situ produced on the surface of carbon nanotubes for ablation of tumor cells

Carbon nanotubes (CNTs) are well known as photo-thermal agents for the ablation of tumor cells, but are limited in the application of photo-thermal therapy (PTT) owing to their low molar extinctions. By coupling the photo-thermal effects of CNTs and the intense localized surface plasmon resonance (LSPR) in the near-infrared (NIR) region of Cu2−xSe nanoparticles (NPs), herein we developed a highly efficient PTT nanohybrids agent by in situ growth of Cu2−xSe NPs on the acid-functionalized CNTs at room temperature. The as-prepared Cu2−xSe/CNT nanohybrids have been found to have intense LSPR in the NIR region and good photo-thermal conversion properties. Moreover, possessing good biocompatibility and dispersibility, the nanohybrids could easily be internalized by cancer cells, and show smart photo-thermal performance, properties which were then successfully applied for photo-thermal therapy in vitro, indicating that the Cu2−xSe/CNT nanohybrids could be a potential photo-thermal therapy agent for the ablation of tumor cells.

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.

Inner filter with carbon quantum dots: A selective sensing platform for detection of hematin in human red cells

Hematin plays a crucial role in various physiological functions, and the determination of hematin in complex biological matrixes is a significant but difficult issue. Considering the unique photophysical/photochemical properties of carbon quantum dots (CQDs) prepared with p-aminobenzoic acid (PABA) and ethanol, a new strategy for the design of fluorescent probes for hematin has been achieved. The proposed sensor array is fabricated based on the inner filter effect (IFE) between hematin and CQDs with phenomenon of selective fluorescence quenching of CQDs which results from the strong absorption of the excitation and emission spectrum of CQDs by hematin. The fluorescence quenching of CQDs is closely related to the amount of hematin and there is a good linear relationship over the range of 0.5-10μM with a detection limit of 0.25μM. Whats more, the fluorescence assay has been successfully applied for hematin sensing in healthy human red cells showing this sensing assay has a great potential prospect for detection of hematin in the complex matrixes.

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.

Aggregation-induced superior peroxidase-like activity of Cu2−xSe nanoparticles for melamine detection

A novel method for sensitive melamine detection based on the aggregation-induced superior peroxidase-like activity of Cu2−xSe capped by sodium polystyrene sulfonate (PSS) (Cu2−xSe@PSS) nanoparticles has been developed. In the presence of melamine, Cu2−xSe@PSS nanoparticles aggregated and exhibited impressive peroxidase-like activity which can accelerate the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to its blue product (oxidized TMB) with H2O2. The enhancement of the absorbance intensity of oxidized TMB at 650 nm showed a good linear relationship with the addition of melamine ranging from 4.7 nM to 29.7 μM. And the detection limit for melamine was as low as 1.2 nM, which was far below the safety limits of melamine ingestion (20 mM in the USA and EU; 8 mM in infant formula in China). Control experiments suggested that the enhancement in the peroxidase-like activity of aggregation for Cu2−xSe@PSS in comparison to its disperse nanoparticles resulted from the ˙OH or O2˙− radical generated.