A Nanoscale Multichannel Closed Bipolar Electrode Array for Electrochemiluminescence Sensing Platform.

In this work, we report a nanoscale multichannel closed bipolar electrode (BPE) array based on the poly(ethylene terephthalate) (PET) membrane for the first time. With our design, oxidants, coreactants, quenchers, and even biomarkers can be detected in a Ru(bpy)3(2+)/TPA (tripropylamine) electrochemiluminescence (ECL) system. The multichannel PET membrane was etched according to our desire by NaOH, and then Au nanofibers were decorated in the inner region of the channel as a BPE array. Using ECL as a signal readout, a series of targets including TPA, Ru(bpy)3(2+), dopamine, H2O2, alpha-fetoprotein (AFP), and carcino-embryonic antigen (CEA) can be detected with this device. The practical application of the proposed multichannel closed BPE array was verified in the detection of AFP and CEA in human serum with satisfying results. This kind of nanoscale device holds promising potential for multianalysis. More importantly, as the PET membrane used in this device can be etched with a desirable diameter (nano- to microscale) and different BPE array densities (ion tracks of 10(8)/cm(2), 10(6)/cm(2), 10(4)/cm(2)), our design can be served as a useful platform for future advances in nanoscale bipolar electrochemistry.

Poly(2,3-diaminonaphthalene) microspheres as a novel quencher for fluorescence-enhanced nucleic acid detection.

In this Communication, we report on the first preparation of conjugation polymer poly(2,3-diaminonaphthalene) (PDAN) microspheres via chemical oxidation polymerization of 2,3-diaminonaphthalene (DAN) monomers by ammonium persulfate (APS) at room temperature. We further demonstrate the use of PDAN microspheres as a novel quencher for fluorescence-enhanced nucleic acid detection.

Coordination polymer nanobelts as an effective sensing platform for fluorescence-enhanced nucleic acid detection.

In this communication, the application of coordination polymer nanobelts (CPNs) assembled from H(2)PtCl(6) and 3,3',5,5'-tetramethylbenzidine (TMB) are explored as an effective fluorescent sensing platform for nucleic acid detection for the first time. The suggested method has a high selectivity down to single-base mismatch. DNA detection is accomplished by the following two steps: (1) CPN binds fluorecent dye-labeled single-stranded DNA (ssDNA) probe via both electrostatic attraction and π-π stacking interactions between unpaired DNA bases and CPN. As a result, the fluorescent dye is brought into close proximity to CPN and substantial fluorescence quenching occurs due to photoinduced electron transfer from the nitrogen atom in CPN to the excited fluorophore. (2) The hybridization of adsorbed ssDNA probe with its target generates a double stranded DNA (dsDNA). The duplex cannot be adsorbed by CPN due to its rigid conformation and the absence of unpaired DNA bases, leading to an obvious fluorescence enhancement.

Rapid fabrication of Au nanoparticle films with the aid of centrifugal force.

In this work, rapid fabrication of Au nanoparticle (Au NP) films has been simply achieved by alternate adsorption of citrate-stabilized Au NPs and poly(diallyldimethylammonium chloride) with the aid of centrifugal force. In contrast to conventional electrostatic assembly, we carried out the assembly process in a centrifuge with a rotating speed of 4000 rpm, where centrifugal force can be imposed on Au NPs. Scanning electron microscopy and cyclic voltammetry were employed to characterize the assembly procedure and the thus-prepared thin solid films. Our results demonstrate that centrifugal force can promote the assembly of Au NPs and therefore enable the rapid fabrication of functional Au NP films. The thus-prepared Au NP films can serve as surface enhanced Raman scatting (SERS) substrates with tunable SERS signal intensity. This method is simple, rapid, and can be used as a general method to rapidly assemble other charged nanoparticles.

A Self-Powered Biosensor with a Flake Electrochromic Display for Electrochemical and Colorimetric Formaldehyde Detection.

The formaldehyde biosensors with the features of cost effectiveness, high specificity, easy operation, and simplicity are urgently desired in routing and field detection of formaldehyde. Here, we report a new design of an enzymatic self-powered biosensor (ESPB) toward formaldehyde detection. The ESPB involves a formaldehyde dehydrogenase/poly-methylene green/buckypaper bioanode as the sensing electrode and a Prussian blue/Au nanoparticles/carbon fiber paper cathode as the electrochromic display. Formaldehyde acts as the fuel to drive the ESPB, relying on that the concentration of formaldehyde can be determined with the ESPB by both directly measuring the variance in short circuit current and observing the color change of the cathode. By measuring the variance in short circuit current, a linear detection range from 0.01 to 0.35 mM and a calculated detection limit of 0.006 mM are obtained, comparable to or better than those reported before. The color change of the cathode can be distinguished easily and exactly via the naked eye after immersing the ESPB in formaldehyde solution for 90 s with the concentration up to 0.35 mM, covering the permissive level of formaldehyde in some standards associated with environmental quality control. Specially, the formaldehyde concentration can be precisely quantified by analyzing the color change of the cathode digitally using the equation of B/(R + G + B). In the following test of real spiked samples of tap water and lake water, the recovery ratios of formaldehyde with the concentrations from 0.010 to 0.045 mM are tested to be between 95 and 100% by both measuring the variance in short circuit current and analyzing the color change of the cathode digitally. In addition, the ESPB exhibits negligible interference from acetaldehyde and ethanol and can be stored at 4 °C for 21 days with a loss of less than 8% in its initial value of short circuit current. Therefore, the ESPB with the capability of working like disposable test paper can be expected as a sensitive, simple, rapid, cost-effective colorimetric method with high selectivity in routing and field formaldehyde detection.

Small Microbial Three-Electrode Cell Based Biosensor for Online Detection of Acute Water Toxicity.

The monitoring of toxicity of water is very important to estimate the safety of drinking water and the level of water pollution. Herein, a small microbial three-electrode cell (M3C) biosensor filled with polystyrene particles was proposed for online monitoring of the acute water toxicity. The peak current of the biosensor related with the performance of the bioanode was regarded as the toxicity indicator, and thus the acute water toxicity could be determined in terms of inhibition ratio by comparing the peak current obtained with water sample to that obtained with nontoxic standard water. The incorporation of polystyrene particles in the electrochemical cell not only reduced the volume of the samples used, but also improved the sensitivity of the biosensor. Experimental conditions including washing time with PBS and the concentration of sodium acetate solution were optimized. The stability of the M3C biosensor under optimal conditions was also investigated. The M3C biosensor was further examined by formaldehyde at the concentration of 0.01%, 0.03%, and 0.05% (v/v), and the corresponding inhibition ratios were 14.6%, 21.6%, and 36.4%, respectively. This work provides a new insight into the development of an online toxicity detector based on M3C biosensor.

A membraneless biofuel cell powered by ethanol and alcoholic beverage.

In this study, we reported on the construction of a stable single-chamber ethanol/O(2) biofuel cell harvesting energy from the ethanol and alcoholic beverage. We prepared a composite film which consisted of partially sulfonated (3-mercaptopropyl)-trimethoxysilane sol-gel (PSSG) and chitosan (CHI). The combination of ion-exchange capacity sol-gel and biopolymer chitosan not only provided the attached sites for mediator MDB and AuNPs to facilitate the electron transfer along the substrate reaction, but also gave the suitable microenvironment to retain the enzyme activity in long term. The ethanol bioanode was constructed with the film coimmobilized dehydrogenase (ADH), Meldola's blue (MDB) and gold nanoparticles (AuNPs). The MDB/AuNPs/PSSG-CHI-ADH composite modified electrode showed prominent electrocatalytic activity towards the oxidation of ethanol. The oxygen biocathode consisted of laccase and AuNPs immobilized on the PSSG-CHI composite membrane. The AuNPs/PSSG-CHI-laccase modified electrode catalyzed four-electron reduction of O(2) to water, without any mediator. The assembled single-chamber biofuel cell exhibited good stability and power output towards ethanol. The open-circuit voltage of this biofuel cell was 860 mV. The maximum power density of the biofuel cell was 1.56 mWcm(-2) at 550 mV. Most interestingly, this biofuel cell showed the similar performance when the alcoholic beverage acted as the fuel. When this biofuel cell ran with wine as the fuel, the maximum power output density was 3.21 mAcm(-2) and the maximum power density was 1.78 mWcm(-2) at 680 mV of the cell voltage. Our system exhibited stable and high power output in the multi-component substrate condition. This cell has great potential for the development and practical application of bioethanol fuel cell.

A simple route to incorporate redox mediator into carbon nanotubes/Nafion composite film and its application to determine NADH at low potential.

Through a new and simple ion-exchange route, two-electron redox mediator thionine has been deliberately incorporated into the carbon nanotubes (CNTs)/Nafion composite film due to the fact that there is strong interaction between any of two among the three materials (ion-exchange process between thionine and Nafion, strong adsorption of thionine by CNTs, and wrapping and solubilizing of CNTs with Nafion). The good homogenization of electron conductor CNTs in the integrated films provides the possibility of three-dimensional electron conductive network. The resulting integrated films exhibited high and stable electrocatalytic activity toward NADH oxidation with the significant decrease of high overpotential, which responds more sensitively more than those modified by thionine or CNTs alone. Such high electrocatalytic activity facilitated the low potential determination of NADH (as low as -0.1 V), which eliminated the interferences from other easily oxidizable species. In a word, the immobilization approach is very simple, timesaving and effective, which could be extended to the immobilization of other cationic redox mediators into the CNTs/Nafion composite film. And these features may offer potential promise for the design of amperometric biosensors.