Short Peptide-Induced Synthesis Of One-Dimensional Inorganic Oxide Nanomaterials

Nanomaterials attracted great attentions due to their abundant morphologies and different properties with their bulk forms.As an important member of the nanomaterials family,1D nanostructures,such as nanotapes,nanorods,nanofibers and nanotubes,shared certain common characteristics with nanoparticles and nanofilms including large surface area and quantum confinement effects.In addition,1D nanomaterials especially 1D inorganic materials,geometrically they offer unique behavior?e.g.1D confined transport of electrons or photons?and therefore endow them novel optical,electrical and magnetic properties.Therefore,the preparation of the 1D inorganic nanomaterials received much attention during the past years.It can be divided into two strategies including directed growth and confined region formation.However,both of them need critical prepararing conditions or special equipment,and lack precise control in structure and morphology.Inspired by the biomineralization of some organisms in nature in which biomineral formed by the control of organic matrix,we tried to construct 1D inorganic nanomaterials with controllable structure and designed performance via the special recognition to ions and catalytic functions of organic templates.Amphiphilic short peptides,composed of a few amino residues,are easy synthesized with low cost.Various morphologies often can be observed owing to their flexible molecular sequences and abundant driving forces.Especially the intermolecular hydrogen bonding drive the peptide sequence arranging along 1D direction and form nanofibers,nanobelts,nanotubes and so on.The shape,size and surface groups of the peptide assembly are easily regulated,so the peptide assemblies are one of the ideal candidates for templating 1D inorganic nanomaterials.On the basis of our research in peptide assembly and biomimetic mineralization,we developed a method to construct 1D branched manganese dioxide,manganese ion doped 1D titanium dioxide and silica/titania hybrid materials by taking advantage of the integrated interaction between the inorganic ions and organic templates,as shown in the following section.?1?We developed a novel method to construct 1D branched MnO₂ nanostructures by performing the disproportionation reaction of KMnO₄ and Mn?NO₃?₂ on I₃K assemblies,in which the nucleation and subsequent growth of MnO₂ were mediated by functional groups?NH₂ and NH₃⁺?of I₃K assemblies.The 1D branched nanostructures possess ultrahigh specific surface area and porous nature.As electrode materials of pseuto-capacitors,they exhibit excellent electrochemical properties compatible with their intricate microstructures.For example,their specific capacitances reached as high as 421 F g^-1,and retained over 93%after 2500 cycles.They also showed well rate capability as the scanning rate increasing from5 to 100 mV s^-1.These results indicate that high performance MnO₂ electrodes can be prepared by subtly regulating their microstructures without introduction of other high conductive substances.At the same time,this investigation provides inspiration for the novel1D structures construction for other inorganic materials by virtue of the abundant and evenly distributed active sites of the organic assemblies.?2?Titanium dioxide is a widely used photocatalytic material due to its excellent photocatalytic property and photochemical stability.However,its relatively poor charge transport property and wide bandgap are two main limitations for its contemporary applications in catalysis and energy harvesting/storage.Ion doping and nanoscale structure are two main stratagem to resolve this problem.Considering the matching of atom radius and energy bandgap,we developed a new method to prepare Mn ions doped 1D titanium dioxide materials by virtue of the catalysis and ion recognition function of peptide templates.Mn ions dopping occurred at the same time of titanium dioxide deposition on the template.According to the result of X ray photoelectron spectroscopy?XPS?,magnesium ions replaced titanium ions in the lattice of TiO₂ as the form of Mn³⁺or Mn⁴⁺.This will narrow the energy bandgap of the materials and improve their light responsibility in visible light region.?3?It is difficult to obtain regulated TiO₂ nanostructures templated by I₃K assemblies due to weak template direction during the mineralization.This is because carboxylate ions that attracted on the template surface can be stripped from the TiBALDH molecule and therefore weaken the interaction between the template and the inorganic species.A co-structure director may be necessary to contact the titania and the template.From our previous research about the biomimetic synthesis of silica we know that silica has intended tendency to interact with peptide templates.Herein,we attempted to increase the template mediation through the co-deposition of silica with titanium dioxide.1D TiO₂/SiO₂ hybrid materials can be obtained with different morphologies and compositions by regulating the molar ratio of silica resource and titania resource.Silica in the hybrids can stablize the titania particles and attract positively charged organic molecules,while titania can act as catalytic center for the degradation of the adsorbed organic molecules.The increased photocatalytic efficiency of 1D TiO2/SiO2 is caused by their synergistic effect.