Fabrication Of Copper-based Oxide Composites On Paper Chip And Its Application In Chemical Sensing

With the increasingly serious medical problems,the development of portable home-based monitoring devices has become a hot research topic recently.Flexible paper-based sensing devices have been widely used for the rapid screening of diseases due to its fascinating features,such as low cost,portability,simple operation,easy to integrate and miniaturize.Though great achievements have been made in the biomedical diagnosis,it still faces many challenges in practical application.The utilization ratio of three-dimensional paper fiber network structure is low,and the type of functionalized transition metal oxides on paper fiber is relatively single,which is difficult to meet the requirements of paper-based photoelectric conversion applications for high-performance paper photoelectrode materials.The mass-transfer rate of paper channel is low,and the microfluidics mass transfer performance of paper-based sensing devices is poor.To overcome the above-mentioned challenges,the new paper chip copper-based oxide composites were fabricated by rationally selecting the functionalized nanomaterials of paper fiber,exploring the nano-functionalization treatment process of paper fiber,and fully regulating and utilizing the three-dimensional paper fiber network structure.Based on the integration of charge separation accelerator and the construction of cascaded sensitized structure,the separation and transmission of charge carriers were directionally controlled,resulting in the enhanced photoelectric signal of paper chip.By the construction of paper electrofluidic and microfluidic structures,the paper micro-functional areas and double-hydrophilic-walls hollow channel were designed,and the high-performance integrated paper-based photoelectrochemical sensing devices were further assembled,which efficaciously promoted the development and application of flexible paper-based sensing devices in the on-site monitoring field.The main research contents of this paper are as follows:（1）Based on the three-dimensional intertwined fiber network structure of paper substrate,the flexible Au paper electrode with both surface conductivity and longitudinal conductivity was prepared by double-sided growth method,which endowed the paper electrode with all-round conductivity and large specific surface area.The Cu₂O polyhedron was first in situ grown on the surface of Au paper electrode to prepare Au-Cu₂O composite-based photocathode.The double-hydrophilic-walls hollow channel was engineered by flexibly handling the hydrophilicity and hydrophobicity of paper chip using the wax-printing technology,which effectively increased the mass-transfer rate of paper channel.And the high-performance double-hydrophilic-walls hollow channel photoelectrochemical paper sensing devices were further assembled.（2）By utilizing the intertwined paper fiber network and reduced graphene oxide（r GO）nanosheets as skeleton and filler,respectively,the r GO nanosheets were both coated on the paper fiber network surface and its macroporous structure via combining the double-sided dripping-drying method and hydrothermal growth method.A large amount of Cu₂O were deposited on the surface of paper-supported three-dimensional interconnected r GO network to fabricate the r GO-Cu₂O composite-based photocathode,and the Cu₂O/Bi VO₄ photosensitive structures were further assembled.An oxygen-hydrogen peroxide-oxygen（O₂-H₂O₂-O₂）circulation system with the photogenerated electrons as fuels and highly active hemin monomers as operators was engineered to realize the recycling of electron acceptor O₂.Based on the functionalized paper chip and poly（methyl methacrylate）cap,a stacked sealed paper-based sensing device was assembled to ensure the self-circulating running of O₂-H₂O₂-O₂ system,which could meet the demand of high-precision paper-based photoelectrochemical sensing.（3）The Au-Cu₂O composite-based dual-photocathode array was prepared by an electrodeposition technique,and then the Cu₂O/GQDs/Ag I cascaded sensitized structures were constructed by selecting the graphene quantum dots（GQDs）and Ag I nanoparticles as the photosensitizers,which availably promoted the photogenerated charge separation and transfer,solving the problem of low photoelectric conversion efficiency of Cu₂O-based single sensitized structure.The assembly of DNA bridge nanostructure was triggered via the duplex specific nuclease-catalyzed target recycling amplification process,and the electron-transfer tunneling distance mediated signal amplification strategy was designed.Based on the spatial resolution of dual-photocathode array,the output of independent working signal and reference signal was designed,and the universal paper-based ratiometric photoelectrochemical sensing device was further constructed.（4）The paper-based Fe OOH/Cu₂O/Cu S photocathode was assembled by using Fe OOH and Cu S as the hole extraction layer and electron transfer/consumption accelerator,repectively.The simultaneous promotion on the photogenerated charge spatial separation and electron acceptor reduction was first achieved benefiting from the good hole extraction ability of Fe OOH and the Cu S-based Cu（II）/Cu（I）redox circular reaction induced by interfacial charge transfer,which not only effectually solved the problem of Cu₂O photocorrosion but also greatly enhanced the cathode photoelectric signal output of paper chip.The target-induced hemin dimer to monomer catalytic switch mediated the generation of electron acceptor O₂.A paper-based homogeneous cathode photoelectrochemical sensing device was fabricated,and the double-hydrophilic-walls hollow channel was used to accelerate the homogeneous mass transfer,which greatly improved the application performance of device.