Shaoxuan Yu

Facile colorimetric method for simple and rapid detection of endotoxin based on counterion-mediated gold nanorods aggregation

Existence of endotoxin in food and injection products indicates bacterial contaminations and therefore poses threat to human health. Herein, a simple and rapid colorimetric method for the effective detection of endotoxin in food and injections based on counterion-mediated gold nanorods aggregation is first proposed. By taking advantage of the color change of unmodified gold nanorods resulted from endotoxin mediated gold nanorods aggregation, endotoxin could be detected in the concentration range of 0.01-0.6 μM. Further, we studied the performance of gold nanorods with different aspect ratios (2.7 and 3.3) in determination of endotoxin and found that gold nanorods with higher aspect ratio (AR) showed superiority in the sensing sensitivity of endotoxin. A good specificity for endotoxin, a detection limit of 0.0084 μM and recoveries ranging from 84% to 109% in spiked food and injection samples are obtained with the colorimetric method. Results demonstrate that the present method provides a novel and effective approach for on-site screening of endotoxin in common products, which is beneficial for monitoring and reducing the risk of bacterial contaminations in food and injections production.

DNA-mediated gold nanoparticle signal transducers for combinatorial logic operations and heavy metal ions sensing

Herein, the structure of two DNA strands which are complementary except fourteen T-T and C-C mismatches was programmed for the design of the combinatorial logic operation by utilizing the different protective capacities of single chain DNA, part-hybridized DNA and completed-hybridized DNA on unmodified gold nanoparticles. In the presence of either Hg(2+) or Ag(+), the T-Hg(2+)-T or C-Ag(+)-C coordination chemistry could lead to the formation of part-hybridized DNA which keeps gold nanoparticles from clumping after the addition of 40 μL 0.2M NaClO4 solution, but the protection would be screened by 120 μL 0.2M NaClO4 solution. While the coexistence of Hg(2+), Ag(+) caused the formation of completed-hybridized DNA and the protection for gold nanoparticles lost in either 40 μL or 120 μL NaClO4 solutions. Benefiting from sharing of the same inputs of Hg(2+) and Ag(+), OR and AND logic gates were easily integrated into a simple colorimetric combinatorial logic operation in one system, which make it possible to execute logic gates in parallel to mimic arithmetic calculations on a binary digit. Furthermore, two other logic gates including INHIBIT1 and INHIBIT2 were realized to integrated with OR logic gate both for simultaneous qualitative discrimination and quantitative determination of Hg(2+) and Ag(+). Results indicate that the developed logic system based on the different protective capacities of DNA structure on gold nanoparticles provides a new pathway for the design of the combinatorial logic operation in one system and presents a useful strategy for development of advanced sensors, which may have potential applications in multiplex chemical analysis and molecular-scale computer design.

Au Promoted Nickel–Iron Layered Double Hydroxide Nanoarrays: A Modular Catalyst Enabling High-Performance Oxygen Evolution

Oxygen evolution reaction (OER) plays a key role in various energy conversion and storage technologies, such as water electrolysis, regenerative fuel cells, and rechargeable metal-air batteries. However, the slow kinetics of OER limit the performance and commercialization of such devices. Herein, we report on NiFe LDH@Au hybrid nanoarrays on Ni foam for much enhanced OER. By hybridization of electronegative Au and NiFe LDH with intrinsic remarkable OER catalytic activity, this modular electrode could drive an overall ultrahigh-performance and robust OER in base with the demand of overpotentials of only 221, 235, and 270 mV to afford 50, 100, and 500 mA cm-2, respectively. Also, it exhibits superior catalytic activity and durability toward OER in 30 wt % KOH.

Dual role of hydrogen peroxide on the oxidase-like activity of nanoceria and its application for colorimetric hydrogen peroxide and glucose sensing

Nanoceria (cerium oxide nanoparticles) exhibits excellent catalytic activity towards chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2), which has been reported. However, the understanding of the interaction between H2O2 and nanoceria is far from comprehensive. Herein, we further studied the interaction between H2O2 and dextran-coated nanoceria and found that H2O2 plays a dual role in nanocerias oxidase activity both as an inhibitor and a promoter, depending on its concentration. At millimolar levels, H2O2 can promote nanocerias oxidase activity; however, micromolar concentrations of H2O2 can inhibit its catalytic activity. In addition, this inhibiting effect is linearly dependent on the concentration of H2O2. Based on these findings, a simple, rapid and highly sensitive colorimetric method was established for the determination of H2O2 with a limit of detection (LOD) of 2.5 μM (3σ/slope) and a linear range from 4−40 μM. When coupled with glucose oxidase, glucose can be detected down to 2 μM in the linear range of 4−40 μM. Furthermore, this method was successfully applied in the determination of glucose in mouse serum samples. With the new understanding of the interaction between H2O2 and nanoceria, applications of nanoceria-based sensors in engineering, biotechnology and environmental chemistry can be further exploited.

Highly Sensitive and Selective Determination of Tertiary Butylhydroquinone in Edible Oils by Competitive Reaction Induced “On–Off–On” Fluorescent Switch

As one of most common synthetic phenolic antioxidants, tertiary butylhydroquinone (TBHQ) has received increasing attention due to the potential risk for liver damage and carcinogenesis. Herein, a simple and rapid fluorescent switchable methodology was developed for highly selective and sensitive determination of TBHQ by utilizing the competitive interaction between the photoinduced electron transfer (PET) effect of carbon dots (CDs)/Fe(III) ions and the complexation reaction of TBHQ/Fe(III) ions. This novel fluorescent switchable sensing platform allows determining TBHQ in a wider range from 0.5 to 80 μg mL(-1) with a low detection limit of 0.01 μg mL(-1). Furthermore, high specificity and good accuracy with recoveries ranging from 94.29 to 105.82% in spiked edible oil samples are obtained with the present method, confirming its applicability for the trace detection of TBHQ in a complex food matrix. Thus, the present method provides a novel and effective fluorescent approach for rapid and specific screening of TBHQ in common products, which is beneficial for monitoring and reducing the risk of TBHQ overuse during food storage.

“Pulling” π-conjugated polyene biomolecules into water: enhancement of light-thermal stability and bioactivity by a facile graphene oxide-based phase-transfer approach

This work demonstrated that graphene oxide (GO) could not only be exploited as a nanovector to efficiently transfer π-conjugated polyene biomolecules from the organic phase to the aqueous phase, but also could enhance light-thermal stability and bioactivity of the transferred π-conjugated polyene biomolecules.

pH-Assisted surface functionalization of selenium nanoparticles with curcumin to achieve enhanced cancer chemopreventive activity

A facile pH-assisted method for synthesizing curcumin-functionalized selenium nanoparticles (SeNPs@Cur) with enhanced cancer chemopreventive activity is proposed in the present work. It is intriguing to observe that by controlling the pH value of the synthetic reaction system, water-insoluble Cur is successfully decorated on the surfaces of SeNPs@Cur through physical adsorption and the possible formation of Se–O bonds. Moreover, the as-prepared nanocomposites possess high drug conjugation efficiency (5.5%), good chemical stability and more uniform sizes and morphologies in comparison with bare SeNPs. Meanwhile, enhanced chemopreventive activity of SeNPs@Cur is demonstrated through the improvements of their free radical scavenging activities and the increases of their cytotoxicities against cancer cells. Cur surface decoration also increases cellular uptake of elemental Se and apoptosis in HepG2 cells. Studies on underlying mechanisms suggest that SeNPs@Cur-induced apoptosis is dependent on the activation of caspases and the overproduction of intracellular ROS. In conclusion, data herein indicate that the strategy to assemble antioxidant ligands on the surface of SeNPs is a potential way to design novel chemopreventive agents with better safety, tolerability and efficacy profiles.