| Recently, with the deep development of nanotechnology, nanocomposite has played an important role in our daily life. Nanocomposite not only possesses the advantages of nanomaterials, such as large surface area, good conductivity, and super mechanical property, but also possesses high catalytic activity, robust adsorption capacity, and good biocompatibility. Based on the searching of abundant papers, using the electrochemiluminescent, photoelectrochemical, and electrochemical properties of nanomaterials, nanocomposites with different morphology and structure was constructed in microfluidic paper-based devices, including quantum dot, gold nanoparticles, and carbon nanotubes, to realize high sensitivity on microfluidic paper-based devices. Luminol-gold nanoparticles and Ru(bpy)32+-graphene nanocomposites were prepared to label functional biomacromolecule, such as antibody and aptamer, to enhance the specificity of the biosensors. The use of such high-sensitivity sensors can offer the application of clinical diagonosis and environment monitoring.1. Fabrication of CdS Quantum Dot-Carbon Nanotube Functionalized Paper Composite Materials and their Application Research in Photoelectrochemical BiosensorsIn this work, a photoelectrochemical (PEC) method was introduced into a microfluidic paper-based analytical device (μ-PAD), and thus, a truly low-cost, simple, portable, and disposable microfluidic PEC origami device (μ-PECOD) with an internal chemiluminescence light source and external digital multimeter (DMM) was demonstrated. The PEC responses of this μ-PECOD were investigated, and the enhancements of photocurrents in μ-PECOD were observed under both external and internal light sources compared with that on a traditional flat electrode counterpart. As a further amplification of the generated photocurrents, an all-solid-state paper supercapacitor was constructed and integrated into the μ-PECOD to collect and store the generated photocurrents. The stored electrical energy could be released instantaneously through the DMM to obtain an amplified (～13-fold) and DMM detectable current as well as a higher sensitivity than the direct photocurrent measurement, allowing the expensive and sophisticated electrochemical workstation or lock-in amplifier to be abandoned. As a model, sandwich adenosine triphosphate (ATP)-binding aptamers were taken as molecular reorganization elements on this μ-PECOD for the sensitive determination of ATP in human serum samples in the linear range from1.0pM to1.0nM with a detection limit of0.2pM. The specificity, reproducibility, and stability of this μ-PECOD were also investigated.2. Fabrication of Porous Semiconductor Polymer-Gold Nanoparticles Functionalized Paper Composite Materials and their Application Research in Electrochemical BiosensorsMolecular imprinting technique is introduced into microfluidic paper-based analytical devices (μ-PADs) through electropolymerization of molecular imprinted polymer (MIP) in a novel Au nanoparticle (AuNP) modified paper working electrode (Au-PWE). This is fabricated through the growth of a AuNP layer on the surfaces of cellulose fibers in the PWE. Due to the porous morphology of paper as well as the high specific surface area and conductivity of the resulting AuNP layer on the cellulose fibers, the effective surface area and the sensitivity of the Au-PWE is enhanced remarkably. Based on this novel MIP-Au-PWE and the principle of origami, a microfluidic MIP-based electro-analytical origami device (μ-MEOD), comprised of one auxiliary pad surrounded by four sample tabs, is developed for the detection of D-glutamic acid in a linear range from1.2nM to125.0nM with a low detection limit of0.2nM. The selectivity, reproducibility, and stability of this μ-MEOD are investigated. This μ-MEOD would provide a new platform for high-throughput, sensitive, specific, and multiplex assay as well as point-of-care diagnosis in public health, environmental monitoring, and the developing world. 3. Fabrication of Electrochemiluminescent Paper Nanocompostie and its Application Research in Wireless Electrophoresis BiosensorIn this work, microfluidic paper-based analytical device (μ-PAD) was further exploited by coupling electrophoretic separation technique for the first time, and a low-cost, simple, portable, and disposable microfluidic paper-based electrophoretic device (μ-PED) with on-column wireless electrogenerated chemiluminescence (ECL) detector (denoted as μ-PED@ECL) was demonstrated. As a proof-of-concept, the performance of this μ-PED@ECL was illustrated by the complete separation and detection of electro-inactive serine, aspartic acid, and lysine within6min, which was realized by household alternating power supply (220V in China) through a novel home-made rectifier, allowing the expensive and sophisticated electrophoretic power supply to be abandoned. Optimizations were performed to achieve both good sensitivity and complete separation with detection limits (3a) of13pM for serine,34pM for aspartic acid, and0.17nM for lysine. The peak height and migration time precisions were<5.0%and<1.5%(n=11) for the three amino acids, respectively. This p.-PED@ECL provided a fast, integrated, and automated potential for multiplex separation and detection on μ-PAD.4. Fabrication of Rhombic TiO2Nanocrystal Composites and their Application Research in Photoelectrochemical BiosensorA novel photoelectrochemical immunosensor using Ru complex as the photoelectrochemical signal-generating molecule, ascorbic acid (AA) as the sacrificial electron donor based on rhombic TiO2nanocrystals (NCs) modified ITO electrode was developed. In order to enhance the photocatalytic activities under UV-vis or visible light irradiation, Ru complex and reduced graphene oxide (RGO) hybrid (Ru-RGO) was prepared, in which Ru complex acts as an electron donor and RGO serves as an electron acceptor in the hybridized species, which facilitates charge separation and suppresses recombination of photoexcited electron-hole pairs in Ru-RGO. The highly crystalline rhombic TiO2NCs were fabricated through a solvothermal technique in anhydrous ethanol. After the ITO/TiO2electrode was coated with chitosan (CS), carcinoma embryonic antigen (CEA) antibodies were covalently conjugated on the surface of the electrode through glutaraldehyde (GLD). Thus, a photoelectrochemical immunosensor for the detection of CEA was developed by monitoring the changes in the photocurrent signals of the electrode resulting from the immunoreaction. The photocurrents were proportional to the logarithmic CEA concentrations, and the linear range of the developed immunosensor was from0.1pg/mL to100ng/mL and with a detection limit of0.059pg/mL. The proposed method showed high sensitivity, stability, reproducibility, and could become a promising technique for immunoassays.5. Composite TiO2Film with Quantum Dots Fabricated Through a Sol-Gel ProcessA novel strategy has been developed to fabricate composite TiO2films with CdTe quantum dots (QDs). Aqueous CdTe QDs with green-, yellow-, and red-emitting were prepared using thioglycolic acid as a capping agent. The QDs revealed high photoluminescence (PL) efficiencies under optimal preparation conditions. TiO2sol was obtained by the controlling hydrolysis of tetrabutyl titanate in ethanol with poly (vinyl pyrrolidone). Diethanolamine was added to prevent the QDs from PL quenching generated by surface defects. After embedding the QDs in composite TiO2film, the PL intensity of the QDs decreased because of the excitation and recombination between the QDs and TiO2. The PL peak wavelength of the QDs in films revealed a slight blue shift compared with their initial ones. The blue shift degree of the PL peaks depended on the properties of the QDs. Red-emitting CdTe QDs revealed a small blue shift of1nm while green-emitting ones revealed a blue shift of7nm. This indicated red-emitting QDs with high stability against incorporation. Facile preparation and excellent properties including high PL brightness, multicolor emission, and high stability make these films important applications in various fields. |
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