Design And Application Of Novel Functional Sensing Interface Based On Nano-materials

Various sensors plays more and more important roles in numerous fields such as clinical diagnosis,food safety and environmental monitoring.Generally,sensors are expected to have the following characteristics,including easy operation,rapid detection,low cost,miniaturization and high sensitivity.However,it's very difficult to achieve all of them in one sensor.We have to choose some of them depending on the application areas.Nano-materials have many unique properties and have been extensively studied.In recent years,micro-fabrication technology is fast developing.New materials and new processing techniques provide more choices for the design of sensors.In this paper,we combined nanomaterials(gold nanoparticles,silver nanoparticle,silicon nanoparticles,graphene oxide and semiconductor nanocrystals)with micro-fabrication technology(microfluidics devices and screen printed electrodes)to build novel functional interfaces for electrochemical and electrochemiluminescence detection(ECL).The details are summarized as follows:1.An electrochemical immunosensing method based on silver nanoparticlesAn electrochemically direct stripping approach based on silver nanoparticles(Ag NPs)labeled with antibody was proposed.To prepare Ag NPs labels,glutathione(GSH)was chemically adsorbed on the surface of Ag NPs through its free thiol groups.Glutaraldehyde was used as a coupling reagent.Its two aldehyde groups reacted with the amino group of GSH adsorbed on the Ag NPs surfaces and the amino groups of antibodies,respectively.The resulting labeled electrochemically active nanoparticles could recognize the proteins specifically via the immobilized antibody.To prove the electrochemical property of labeled Ag NPs,human IgG was used as a model protein sample to be immobilized on a screen printed electrode(SPE)and the goat-anti-human IgG labeled Ag NPs was added onto the surface of the SPE,followed by differential pulse voltammetric(DPV)method.With the oxidation of Ag NPs labels coupled on the electrodes,the concentration of hIgG could be assayed directly.The dynamic concentration was in the range of 1.0-1000 ng/mL and the detection limit was 0.4 ng/mL(S/N = 3).In addition,the presented method was also compared with indirect electrochemical stripping detection by dissolving Ag NPs labels with nitric acids and showed advantages such as lower detection limit,rapidity and simplicity.2.Highly sensitive ratiometric electrochemiluminescence biosensor for microRNAs detection based on cyclic enzyme amplification and resonance energy transferFalse positive or negative errors may occur during the detection of trace level analytes due to instrumental efficiency or some environmental change.Ratiometric assay,in which the quantification depending on the ratio of two signals instead of absolute values,is an ideal approach to eliminate these interference factors and make the detection more convincing.Enzyme-assisted amplification is a powerful tool in bioanalysis.Here we developed an ECL ratiometric assay with cyclic enzymatic amplification for the first time.And the sensitivity is further improved by the distance dependent resonance energy transfer between gold nanoparticles(Au NPs),luminol-gold nanoparticles(L-Au NPs)and semiconductor nanocrystals(NCs).Target miRNA may be quantified by the ratio of the cathode signal from CdS and anode signal from luminol.Au-probe 1 would enhance the ECL intensity of CdS.L-Au-probe 2 would quench the ECL signal from CdS NC and bring the ECL signal of luminol.This novel ratiometric method is highly sensitive and selective,which may be a powerful tool for biomedical research and clinical diagnostics.3.A portable thermo-powered high-throughput visual electrochemiluminescence sensorWe describe a portable thermo-powered high-throughput visual ECLsensor for the first time.This sensor is composed of a tiny power supply device based onthermal-electrical conversion and a facile prepared array electrode.The ECL detection could be conducted with thermo-power,which is easily accessible.For example,hot water,a bonfire,or a lighted candle enables the detection to be conducted.And the assay can be directly monitored by naked eyes semi quantitatively or smart phones quantitatively.Combined with transparent electrode and array micro-reactors,a portable high-throughput sensor was achieved.The portable device,avoiding the use of electrochemical workstation to generate potential and photomultiplier tube(PMT)to receive signal,is not only a valuable addition for traditional methods,but also a suitable device for field operation or point-of-care testing.4.A graphene oxide/poly(dimethylsiloxane)composite for remote control of localized wettabilityIn this work we report an optical-driving approach to realize remote control of reversible localized wettability based on a facile prepared graphene oxide/poly(dimethylsiloxane)(PDMS)composite combining with a thermo-responsive polymer,poly(N-isopropylacrylamide)(PNIPAAm).We applied NIR laser illumination,a non-contact,penetrative and flexible approach,instead of traditional Joule heating,to finely control the spatially distribution of temperature.The temperature change brings the switch between hydrophilicity and hydrophobicity because of the grafted thermal-responsive polymer.At room temperature PNIPAAm presents a swollen hydrated state because of H-bonding formation between PNIPAAm chains and water molecules.When a laser beam illuminates this composite,embedded GO absorbs light energy and converts it to thermal energy to heat up the exposure region.After the temperature increases to LCST,H-bonding in the PNIP AAm breaks up and the hydrophobic interactions become predominant,which leads to a compact conformation with hydrophobic property.And reversible spatially controlled protein adsorption has been achieved successfully based on this work.It holds great potential in biomedicine and microfluidics area,such as pattern cell capture,drug release or bio-adhesion.