Preparation Of Biomass/metal Or Semiconductor Composites And Their Application In Flexible Electronics

With the increasing environmental burden caused by the non-degradable fossil based synthetic materials,developing biomass-based composites has become an urgent demand.Biopolymers,such as lignocellulose,chitin/chitosan and alginate,are abundant,renewable,biodegradable.And more importantly,these biopolymers contain rich functional groups,such as hydroxyl,amino,carboxyl groups and so on,thus,they can be further functionalized with organic or inorganic functional materials.This paper is focusing on developing novel biomass(e.g.chitosan,sodium alginate and cellulose fiber)/ metal nanoparticles and semiconductor nanoparticles composite materials with high performance.The active groups and aggregation structure of biomass template might affect the morphology,nucleation and growth of metal and semiconductor crystals,producing high-performance biomass-based composite functional materials.The main contents of this thesis are as follow:1.A novel and simple method was developed for preparing biomass-perovskite nanocomposites through biomineralization.Using chitosan as template,the chitosan/perovskite composite film with smaller crystal size,more uniform crystal coverage and smoother surface can be obtained.The influence of chitosan on the nucleation and growth of perovskite crystals is preliminarily explored.This chitosan/perovskite composited thin film is further applied to the planar heterojunction solar cell,and its photoelectric conversion efficiency has been improved compared with the control sample.2.Silver nanowire can be synthesized successfully by a mild and green aqueous method using sodium alginate as a capping agent and ascorbic acid as reducing agent.The obtained silver nanowires have a large length-diameter ratio with diameter of 50-250 nm and the length of 5-40 ?m.The properties of silver nanowires can be controlled by simply adjusting the ratio of sodium alginate and silver nitrate and the reaction temperature.In addition,a new multifunctional smart fabric with uniform coating of silver nanowires was prepared through a simple "dipping and drying" method.The smart fabric has ultra-low surface resistance(0.02 ?/sq),and excellent mechanical,chemical stability,excellent electrochemical performance and photothermal conversion properties.3.Two different nitrogen containing polymers(including chitosan,polydopamine)were applied to functionalize biomass substrates to anchor the catalysts,and then highly conductive and flexible papers or films were obtained through electroless deposition.First,the chitosan film was used to adsorb the catalyst directly,and then the copper nanoparticles were deposited on the surface by electroless deposition.The high conductive chitosan film(0.02 ?/sq)was obtained.However,the stability of the conductive film was poor and the adhesion strength between the metal layer and the chitosan film was weak.Inspired by the high adhesion ability of shell mussels,polydopamine was formed on the surface of different biomass substrates(including cellulose paper,cotton fabric and cotton yarns)to immobilize catalysts,and then insitu grow Cu or Ag nanoparticles by electroless deposition.The obtained composited substrates with super-hydrophobic surface have excellent self-cleaning performance.In addition,the composited substrates also have high conductivity(the sheet resistance is less than 1 ?/sq)and conductive stability.They remain highly conductive even after bending or folding for over 1000 times.It is also found that the conductive paper has excellent electromagnetic shielding property and photothermal conversion property.In addition,the application of conductive paper in glucose sensing and supercapacitors has been investigated,and excellent performance has been achieved.4.A new composited paper substrate is obtained using commercial copy paper and polypropylene film by hot press to obtain more smooth biomass substrates.Compared with copy paper,the composited paper has significantly improved mechanical property and solvent stability,and the surface roughness of the composite paper is greatly reduced.And we use two different compounds with amino groups(including dopamine,amino-cellulose)to modify the composited paper.The dopamine molecule is further adsorbed on the surface of the composited paper,and then the copper nanoparticles are electrolessly deposited on the composited paper.Highly conductive paper with sheet resistance of 1?/sq can be obtained,and it has superhydrophobic surface.It is found the obtained Cu NPs/ composited paper has stronger adhesion and lower surface roughness when the surface of the composite paper is coarsened.Besides,it is found that the obtained Cu NPs/ composite paper has high reflectivity,so it can be applied to flexible electronic devices.Amino-cellulose is self-assembled on the surface of the paper to immobilize the catalysts,and then the copper nanoparticles are deposited on cellulose paper by electroless deposition to prepare composite paper with highly uniform,conductivity and stability.The effects of the three nitrogen-based polymers on the nucleation and growth of copper nanoparticles were explored.The surface morphology,electrical conductivity,mechanical properties,thermal stability and electrical stability of the Cu nanoparticles composited substrate were systematically explored.