Mingjun Gao

Morphology Tailoring of Nano/Micro-Structured Conductive Polymers, Composites and their Applications in Chemical Sensors

Conductive polymer is one of the important multi-functional materials. It has many applications in light-emitting diodes, chemical sensors, biosensors, et al. This paper provides a relatively comprehensive review on the progress of conductive polymer and composite as sensitive film for sensors to chemical vapors including patents, papers and our preliminary research results. Especially, the feature of conjugated polymers, the processing technology, doping characteristics and some factors affecting gas responses are discussed. Otherwise, the developments of nanostructured conductive polymer and organic-inorganic hybrid film sensor with high sensitivity and rapid response to vapors are also described, and some suggestions are proposed.

Preparation of Low-Dimensional Carbon Nanomaterials and Its Improvement of Visible Light Activity

ZnO and its nanocomposites have been received good progresses in new energy, photocatalysts, environmental fields. However, to enhance the visible light activity of ZnO is still a great challenge. Among so many methods of modifying ZnO, carbon-doping or nanocomposite with carbon nanomaterials are simple and effective approaches. In this study, low-dimensional carbon nanomaterials were synthesized with biomass waste (such as com straw) referring to the method of chemical synthesis of graphene oxide. ZnO nanosheets/carbon nanocomposites were prepared utilizing the interaction between surface chemical groups of ZnO nanosheets and low-dimensional carbon nanomaterials produced with biomass waste. A series of characterizations were carried out. The results indicated that the band edge of nanocomposite was extended to the whole visible light and NIR. The photoconductive response to weak visible light and 808 nm NIR (near infrared) were studied based on interdigital electrodes of Au on flexible polymer film substrate with casting method. The results indicated that the ZnO/carbon nanocomposite holded photo-switching behavior, the response and recovery were very rapidly. This illustrated that the resulting nanocomposites showed good activities to weak visible light and NIR. Photocatalytic efficiency was examined by selecting typical organic pollutants, some good results were also obtained. It would be potential applications in photocatalysts, self-cleaning films, NIR detector, coatings, and organic pollutants treatment of environmental fields. It would be low-cost, effective, general method to treat the surface of several metal oxides.

Preparation and Properties of Interconnected NiS Nanoparticle Network with Amphiphilic Polymers

Low-dimensional functional nanocomposite with visible light activity is one of hot-spots fields in chemistry, physics and materials according to the demands of new energy and environmental fields. To simulate the process of photosynthesis of nanomaterials, in this study, NiS nanomaterials were synthesized with amphiphilic polymers as soft template. The nanocomposite with integrated multi-functionalities were characterized with several approaches. The photoconductive responses to weak visible light and 808 nm NIR (near infrared) were studied based on interdigital electrodes of Au on flexible PET (polyethylene terephthalate) film substrate with casting method. The results indicated that the resulting NiS nanocomposite is core/shell structure, showing interconnected network, looks like honeycomb, and the nanocomposite with integrated multi-functionalities exhibited photo-switching behaviors, the ratio of On/Off was 2–3 orders of magnitudes, the response and recovery were very rapidly. It would be developed the intelligent nanocomposites with external stimuli responses, light detector to NIR, biomimetic materials, nano-machine controlled by light, environmental fields, and so on.

GO/DNA/Au/PANi Nanocomposite with High Photoconductive Responses to Visible Light and NIR

In synthesis of nanomaterials with bottom-up approach, DNA (deoxyribonucleic acid) chain segment took an important role in self-assembly of nano/micro-structured materials. DNA chain segment not only has good recognition characteristics, but also holds excellent transporting properties of delivery for drugs, protein or gene. To functionalize and smart the nanocomposites for applications in several devices, in this paper, single-stranded DNA chain and graphene oxide (GO) were hybridized, and Au nanoparticles were formed in situ with chloroauric acid and aniline as reducing agent. The GO/DNA/Au/PANi (polyaniline) nanocomposite were characterized by several approaches. The photoconductive responses to weak visible light and 808 nm NIR (near infrared) were studied based on interdigital electrodes of Au on flexible polymer film substrate with casting method. The results indicate that the resulting nanocomposite exhibits good photo-switching behaviors, the ratio of On/Off is 1–2 orders of magnitudes, while the response and recovery are very rapidly. It can be used in developing an intelligent nano-carriers with external stimuli responses, light detector to NIR, nano-machine controlled by light, biomimetic materials, and so on.

Dispersion of Graphene Oxide in Polyvinylidene Difluoride and Its Improvement of Photoresponse Properties of Nanocomposite

Graphene oxide (GO) and its nanocomposites are widely used in energy storage devices, membrane separation, multi-functional materials due to their good charge transferring property and excellent mechanical, physical, chemical properties. The performances of materials and devices are strongly dependent on the dispersion effects of GO in matrix. In the applications of polymer/GO nanocomposites, the re-dispersion of dried GO in matrix with good effects is still having some difficulties. Good dispersion of GO solution with polymer aqueous would be obtained easily. However, the dispersion of GO solution in non-aqueous polymers is still a great challenge. In this paper, attempts of the dispersion of GO solution in non-aqueous polymers were carried out with oil/water interface mixed approach. In the study, PVDF [poly-(vinylidene difluoride)] selected as representative polymer is based on the following reason. PVDF is a well-known organic multi-functional polymer, which is widely used in several devices due to its outstanding piezoelectric, pyroelectric, and dielectric performance. PVDF/GO nanocomposites were obtained with interface blend, and a series of characterizations were performed. The photoconductive responses to weak visible light and 808 nm NIR (near infrared) were studied based on interdigital electrodes of Au on flexible polymer film substrate with casting method. The results indicate that the GO has good dispersion in PVDF matrix and no obvious aggregation of GO is observed. The resulting nanocomposite exhibits good photo-switching behavior to visible light, while the response and recovery are very rapidly. The response to weak 808 nm NIR is relatively weak, this may be the results of PVDF possessing some absorbance to NIR. It can be seen that an intelligent composite film with external stimuli responses is developed and can be used in many fields, such as electronic skin, sensors and actuators, information storage, artificial muscle, biomimetic films, membrane separation controlled with external stimuli.

Preparation, modification, morphology tailor and application of conjugated conductive polymer in chemical sensors

Polyaniline nanotube was prepared with aid of lactic acid assembly. A chemical prototype sensor was constructed based on nanotube-structured polyaniline and two typical structured chemical sensors, one is an interdigital electrodes on flexible polymer substrate, the other is a highly sensitive quartz resonators. The gas-sensing behavior of the two typical sensors to some organic vapors operating at room temperature was investigated. Results showed rapid response, and good reversibility of these two typical sensors. The response time is 10-20 s, the reversible time is about 100 s. This study provides a simple approach for preparation of materials needed for a chemical sensor to selected organic volatiles with rapid response or organic flexible nanoelectronic devices.