Single Pt-Pd Bimetallic Nanoparticle Electrode: Controllable Fabrication and Unique Electrocatalytic Performance for the Methanol Oxidation Reaction.

Understanding the electrocatalytic activity at single nanoparticles/nanoclusters level is extremely important. In this work, a method for the electro-deposition of single Pt-Pd nanoparticles (NPs) is described using a single nanopore electrode as a template. The electro-deposition process was investigated carefully and the results show that the process is controlled by diffusion and electro-crystallization process, simultaneously, and the glass sheath property around the nanopore has a large impact on the formation of single Pt-Pd NPs due to the "edge effect". The prepared single Pt-Pd NPs exhibit excellent electrocatalytic activity in the methanol oxidation reaction, which can be used to screen electrocatalysts with high efficiency for utility in the energy field.

A visible light photoelectrochemical biosensor coupling enzyme-inhibition for organophosphates monitoring based on a dual-functional Cd(0.5)Zn(0.5)S-reduced graphene oxide nanocomposite.

A novel visible light photoelectrochemical (PEC) platform coupled with enzyme-inhibition for rapid and sensitive determination of organophosphates (OPs) was constructed based on a dual-functional Cd0.5Zn0.5S-reduced graphene oxide (Cd0.5Zn0.5S-rGO) nanocomposite. Due to the inherent biocompatibility of the Cd0.5Zn0.5S-rGO nanocomposite, acetylcholinesterase (AChE) immobilized on the Cd0.5Zn0.5S-rGO modified electrode can hydrolyze acetylthiocholine chloride into thiocholine, which could increase the photocurrent of the enzyme electrode, and the further inhibition of OPs on the enzyme electrode could decrease the photocurrent response. Based on the notable change in the PEC response of the AChE-Cd0.5Zn0.5S-rGO modified electrode and using Dursban as a model, a simple and effective way for PEC monitoring of OPs is proposed, which showed a wide linear range of 0.001-1 µg mL(-1) with a low detection limit of 0.3 ng mL(-1) (S/N = 3). Moreover, the biosensor was successfully challenged with water samples, demonstrating a new method for rapid and sensitive screening/evaluating exposure to organophosphorus pesticides and other hazardous substances.

Design and evaluate the performance of a mechanical system for the release of Harmonia axyridis adults.

Harmonia axyridis (H. axyridis) is the natural enemy of many aphid species. Traditional manual release of H. axyridis adults requires substantial manpower, and release efficiency is low. Automatic mechanical devices can improve the efficiency of delivery. Based on H. axyridis adults' morphological size, a prototype release system for H. axyridis was designed, which considered the adhesion characteristics of H. axyridis adults. According to the measured physical characteristics of H. axyridis adults, the structural parameters of the mechanical system for the release of the H. axyridis adults were determined. The relationship of the quantity of release, the impeller rotating speed, and the time for the release of H. axyridis adults were constructed. The mechanism can quantitatively adjust the number of H. axyridis adults to meet a certain H. axyridis-aphids ratio. Combining the image processing technology with the camera function of a mobile phone, the maximum cross-sectional area method was used to count the H. axyridis adults in the designated area. Results showed that the impeller rotating speed had a significant effect on the survival rate of the H. axyridis adults. When the airflow velocities were 29.5 m/s and 38.3 m/s, the survival rates of the H. axyridis adults were 93.8% and 94.5% at 4.2 rpm. The adhesion rate of the H. axyridis adults was 2.5%-4.6%. This work will provide technical support for the research of biological control.

Enhanced peroxydisulfate electrochemiluminescence for dopamine biosensing based on Au nanoparticle decorated reduced graphene oxide.

This work reports a novel strategy to amplify the electrochemiluminescence (ECL) signal of peroxydisulfate solution based on the Au nanoparticle decorated reduced graphene oxide (Au NP-RGO), and further an ECL biosensor for sensitive and selective detection of dopamine (DA) was constructed. Due to the synergistic amplification of Au NPs and RGO, the ECL signal of peroxydisulfate solution on the Au NP-RGO modified electrode was about 5-fold enhanced compared to that of the bare electrode with the ECL onset potential positively shifted from -1.2 V to -0.9 V. More interestingly, the ECL intensity of peroxydisulfate solution increased with the increase of DA concentration, based on which an ECL biosensor for DA determination was fabricated. The as-prepared solid-state ECL DA sensor showed a wide linear response of 0.02-40 µM with a detection limit of 6.7 nM (S/N = 3). Moreover, we expect this work would open up a new field in the application of peroxydisulfate solution ECL for highly sensitive bioassays.

TiO2-decorated graphene nanohybrids for fabricating an amperometric acetylcholinesterase biosensor.

This work describes a highly sensitive and rapid amperometric biosensor for organophosphate compounds (OPs) based on immobilization of acetylcholinesterase (AChE) on a novel TiO(2)-decorated graphene (TiO(2)-G) nanohybrid, which was constructed by in situ growth of TiO(2) nanoparticles (NPs) on the graphene sheet. The well-dispersed TiO(2) NPs eliminated the restacking of TiO(2)-G nanohybrids. Due to the integrating of TiO(2)-G nanohybrids, the as-prepared biosensor showed high affinity to acetylthiocholine (ATCl) with a Michaelis-Menten constant (K(m)) value of 0.22 mM, and rapid inhibition time (3 min). Further, based on the inhibition of OPs on the enzymatic activity of the immobilized AChE, and using carbaryl as a model compound, the inhibition of carbaryl was proportional to its concentration ranging from 0.001 to 0.015 and 0.015 to 2 µg mL(-1) with a detection limit of 0.3 ng mL(-1) (S/N = 3). The developed biosensor exhibited a good performance for organophosphate pesticide detection, including good reproducibility and acceptable stability, which provided a new and promising tool for the analysis of enzyme inhibitors.

Fabricating photoelectrochemical aptasensor for selectively monitoring microcystin-LR residues in fish based on visible light-responsive BiOBr nanoflakes/N-doped graphene photoelectrode.

The presence of microcystins in fish has been augmenting the risk of toxicity to animal and human health. Herein, a selective and sensitive method for detecting microcystin-LR (MC-LR) in fish samples by integrating the photoelectrochemical (PEC) technique and the specific recognition ability of aptamer was developed. Specifically, as an efficient PEC transducer, the BiOBr nanoflakes/N-doped graphene p-n heterojunction electrode was utilized as the aptamer immobilization platform via the π-π stacking interaction, which would be a biosensor enabling the convenient and exquisite PEC analysis. Subsequently, the PEC response of constructed aptasensor was specific binding to MC-LR. Other isoforms did not interfere with the detection process, and thus, it could be applied for the highly selective determination of MC-LR level. Under the optimized condition, the PEC signal versus the logarithm of the MC-LR concentration was in good linear relationship ranging from 0.1pM to 100nM with detection limit about 0.03pM. The constructed method was employed to analyze fish samples collected from the local supermarket. The overall analytical recovery of MC-LR in the fish matrices ranged from 97.8 to 101.6%, with relative standard deviation (RSD) of 2.52-5.14%, implying it would have great potential in farm product analysis.

Label-free impedimetric aptasensor for detection of femtomole level acetamiprid using gold nanoparticles decorated multiwalled carbon nanotube-reduced graphene oxide nanoribbon composites.

Gold nanoparticles (Au NPs) decorated multiwalled carbon nanotube-reduced graphene oxide nanoribbon (Au/MWCNT-rGONR) composites were synthesized by a one-pot reaction. By employing the resulting Au/MWCNT-rGONR composites as the support for aptamer immobilization, we developed an ultrasensitive label-free electrochemical impedimetric aptasensor for acetamiprid detection, which was based on that the variation of electron transfer resistance was relevant to the formation of acetamiprid-aptamer complex at the modified electrode surface. Compared with pure Au NPs and MWCNT-rGONR, the Au/MWCNT-rGONR composites modified electrode was the most sensitive aptasensing platform for the determination of acetamiprid. The proposed aptasensor displayed a linear response for acetamiprid in the range from 5×10(-14) M to 1×10(-5) M with an extremely low detection limit of 1.7×10(-14) M (S/N=3). In addition, this impedimetric aptasensor possessed great advantages including the simple operation process, low-cost, selectivity and sensitivity, which provided a promising model for the aptamer-based detection with a direct impedimetric method.

Amplified solid-state electrochemiluminescence detection of cholesterol in near-infrared range based on CdTe quantum dots decorated multiwalled carbon nanotubes@reduced graphene oxide nanoribbons.

An amplified solid-state electrochemiluminescence (ECL) biosensor for detection of cholesterol in near-infrared (NIR) range was constructed based on CdTe quantum dots (QDs) decorated multiwalled carbon nanotubes@reduced graphene nanoribbons (CdTe-MWCNTs@rGONRs), which were prepared by electrostatic interactions. The CdTe QDs decorated on the MWCNTs@rGONRs resulted in the amplified ECL intensity by ~4.5 fold and decreased onset potential by ~100 mV. By immobilization of the cholesterol oxidase (ChOx) and NIR CdTe-MWCNTs@rGONRs on the electrode surface, a solid-state ECL biosensor for cholesterol detection was constructed. When cholesterol was added to the detection solution, the immobilized ChOx catalyzed the oxidation of cholesterol to generate H2O2, which could be used as the co-reactant in the ECL system of CdTe-MWCNTs@rGONRs. The as-prepared biosensor exhibited good performance for cholesterol detection including good reproducibility, selectivity, and acceptable linear range from 1 µM to 1mM with a relative low detection limit of 0.33 µM (S/N=3). The biosensor was successfully applied to the determination of cholesterol in biological fluid and food sample, which would open a new possibility for development of solid-state ECL biosensors with NIR emitters.

Enhanced non-enzymatic glucose sensing based on copper nanoparticles decorated nitrogen-doped graphene.

Copper nanoparticles (NPs) decorated nitrogen-doped graphene (Cu-N-G) was prepared by a facile thermal treatment, and further employed as a novel sensing material for fabricating the sensitive non-enzymatic glucose sensor. Compared with pure Cu NPs, the Cu-N-G showed enhanced electrocatalytic activity to glucose oxidation due to the integration of N-G, which exhibited the oxidation peak current of glucose ca. 23-fold higher than that of pure Cu NPs. The presented sensor showed excellent performances for glucose detection including wide linear range of 0.004-4.5 mM, low detection limit (1.3 µM, S/N=3), high sensitivity (48.13 µA mM(-1)), fast response time (<5 s), good selectivity to the general coexisted interferences, etc. Such properties would promote the potential application of the nitrogen-doped graphene as enhanced materials in fabricating sensors for chemical and biochemical analysis.

Polyoxometalate@magnetic graphene as versatile immobilization matrix of Ru(bpy)3(2+) for sensitive magneto-controlled electrochemiluminescence sensor and its application in biosensing.

We demonstrated here the exploration of polyoxometalate (POM) coated magnetic Fe3O4/reduced graphene oxide (POM@mrGO) composite as the versatile immobilization matrix for the electrochemiluminescence (ECL) agent Ru(bpy)3(2+). The effective modification of Ru(bpy)3(2+)/POM@mrGO hybrid simply involved using magnetic electrode showed 10-fold ECL intensity increase than that observed for Ru(bpy)3(2+)/Nafion@mrGO to the same concentration of nicotinamide adenine dinucleotide (NADH), which is largely due to POM׳s good electrocatalytic activity towards NADH oxidation. These findings allowed the stable and ultrasensitive ECL detection of NADH as low as 0.1 nM. The good stability and high sensitivity of the magneto-controlled ECL sensor enabled us to explore the feasibility of applying the sensing platform to fabricating the ECL biosensors in which the NADH was produced from the dehydrogenase-based enzymatic reaction in the presence of NAD(+) cofactor. With L-lactate dehydrogenase as a model, a L-lactate biosensor was successfully constructed where we showed that the ECL intensity of the biosensor increased with the increasing L-lactate concentration. Excellent performance of the presented biosensor has been achieved including a wide linear range extended from 5.0×10(-9) M to 5.0×10(-4) M and an extremely low detection limit of 0.4 nM. Such sensing strategy combines enzymatic selectivity with simple sensor preparation can be used as a new and biocompatible platform for dehydrogenase-based ECL biosensing.

A highly sensitive and rapid organophosphate biosensor based on enhancement of CdS-decorated graphene nanocomposite.

This work reports a rapid and sensitive organophosphates (OPs) amperometric biosensor based on acetylcholinesterase (AChE) immobilized on CdS-decorated graphene (CdS-G) nanocomposite. The as-prepared biosensor shows high affinity to acetylthiocholine (ATCl) with a Michaelis-Menten constant (K(m)) value of 0.24 mM. A rapid inhibition time (2 min) is obtained due to the integration of the CdS-G nanocomposite. Based on the inhibition of OPs on the enzymatic activity of the immobilized AChE, and used carbaryl as the model compound, the resulting biosensor exhibits excellent performance for OPs detection including good reproducibility, acceptable stability, and a reliable linear relationship between the inhibition and log[carbaryl] from 2 ng mL⁻¹ up to 2 µg mL⁻¹ with a detection limit of 0.7 ng mL⁻¹,which provides a new promising tool for analysis of enzyme inhibitors.