Preparation And Properties Of TiO₂ Nanorod Arrays On ITO

TiO₂ nanorod arrays as an excellent one-dimensional nanomaterials has been widely attentioned by researchers because of its unique performance,such as highly electron transfer efficiency,electron-hole pairs easily separated and strongly light scattering effect,and so on.In recent years,it has been widely used in fuel-sensing batteries,sewage treatment,gas sensors and other fields.Therefore,the research on the crystal structure and morphology of TiO₂ nanorod arrays has also become the focus of researchers.In this paper,we used TiCl₄ as titanium source,H₂O as oxygen source,HCl as inhibitors,ITO?Indium Tin Oxides?glass as a substrate to prepare TiO₂ nanorod arrays by one step hydrothermal method.We explores the effects of reaction time,reaction temperature,hydrochloric acid concentration,TiCl₄ content and annealing temperature on the crystalline phase content,crystal structure,surface morphology,photocatalytic activity and hydrophilicity of TiO₂/ITO composites.Meanwhile,anazlying the properties of modified samples which added PVP,tartaric acid and citric acid.It showed that:?1?High-density anatase Ti O₂ nanorod arrays were successfully prepared by one step hydrothermal method on ITO conductive glass.The nanorod arrays were tightly attached on the ITO,forming the TiO₂/ITO composite materials.The nanorod growed along[101]with the diameter of about 230 nm and the length of about 2.5?m,the nanorod grow neatly,arranged closely,forming a neat array-like structure.?2?The effects of different reaction parameters on the crystal phase and morphology of TiO₂ nanorod arrays were investigated.The increase of hydrochloric acid concentration gives TiO₂ nanorods a suitable growth environment,the TiO₂nanorod basiclly complete development at the concentration of HCl was 6M,which were with the diameter of about 150 nm and the length of about 4?m,showing as arrays.With the concentration rise to 8M,the generation of TiO₂ is reduced,and the nanorods produce shedding on the ITO glass,peracid conditions are not conducive to the growth of TiO₂ nanorods.As the reaction temperature increases,the atomic energy gain,activity increased,move to a more appropriate lattice position,making the formation of better crystalline TiO₂ crystals,more conducive to the formation of nanorod arrays.the TiO₂ nanorod with the diameter of about 230 nm and the length of about 4?m at 160?,When the reaction temperature exceeds 180?,the volume of nanorods becomes larger and larger,the nanorods appear the branched structure again,the specific surface area becomes smaller.With the increase of the reaction time at 7h,the Ti atoms have sufficient time to contact with the O atoms due to sufficient time for hydrothermal reaction,which leads to the formation of a large amount of Ti O₂ nanorods and the formation of close and tidy arrayed structure on the ITO substrate,the nanorods grow too dense due to the longer reaction time,the top squeeze each other so that there has been a phenomenon of fracture.With the content of TiCl₄ increased,there is sufficient raw material for nucleation reaction,the density of TiO₂ nanorods is increasing,the diameter becomes larger,the TiO₂ nanorod with the diameter of 240-380 nm and the length of 3.5-4?m at 0.20ml,the content of nanorods is obviously increased,showing a neat array structure.With the increase of annealing temperature,the bigger of the diameter of grain,the larger of the specific surface area,the nanorods showed the best morphology at 450?,as the annealing temperature increase,new small nanorods grow from the original nanorods,forming numerous tiny branches,the structure of the nanorod arrays is destroyed,and due to excessive growth of nanorods,a large number of nanorods appeared"lodging"phenomenon,which lead to the reduction of photocatalytic activity points.?3?The photocatalytic and hydrophilic properties of TiO₂ nanorod arrays were investigated.Photocatalytic experiments using methyl orange and acid red as degradants,high pressure mercury lamp under the methyl orange and acid red absorbance as a standard,the best photocatalytic degradation can reach 100%.Hydrophilicity detection is based on the optical contact angle when the droplet is tiled.When the hydrophilicity is the best,the optical contact angle of the sample after UV irradiation is 8.1?,which almost tiled on the sample surface.?4?The effects of adding different additives on the crystal phase and morphology of TiO₂ nanorod arrays were investigated.With the increase of the content of PVP,the diameter of nanorods showed an increase first and then decrease and then increased.The diameter of nanorods is about 77-120nm at the content of PVP was 0.5g,nanorods growth density,large specific surface area,there has been a neat array-like structure.With the increase of tartaric acid content,the diameter of nanorods first decreased and then increased.The diameter of nanorods is about 77-200nm at the content of tartaric acid was 0.5g,the morphology of nanorods also changed from"dendrites"to neatly arranged arrays.This is because the addition of tartaric acid promotes the growth of anatase nuclei,in the titanium precursor concentration under certain conditions,the density of TiO₂ nanorods growing more closely,the diameter will be reduced,However,due to the strong chelating ability of tartaric acid and Ti center,the condensation between titanium complexes is slowed down,Therefore,with the tartaric acid addition continues to increase,the diameter of TiO₂ nanorods also increases.With the increase of the content of citric acid,the diameter of nanorods shows a trend of decreasing and then increasing.The diameter of nanorods is about 78-230nm at the content of citric acid was 0.4g,TiO₂ nanorods show the best morphology.Citrate will coordinate with titanium ions,when the content of citrate increases,the carboxylic acid groups in the system gradually become excess,the coordination of citrate and titanium decreases,the volume of polymer formed decreases and the particle size decreases,when the citric acid content continues to increase,most of the titanium ions in the solution are coordinated with the citrate groups to form a polymer,the spacing between the polymers becomes smaller,the probability of collision with each other greatly increases,and the particle size also increases.?5?The photocatalytic and hydrophilic properties of TiO₂ nanorod arrays were investigated after adding different additives.Photocatalytic experiments using methyl orange and acid red as degradants,high pressure mercury lamp under the methyl orange and acid red absorbance as a standard,the best photocatalytic degradation can reach100%.Hydrophilicity detection is based on the optical contact angle when the droplet is tiled.When the hydrophilicity is the best,the optical contact angle of the sample after UV irradiation is 5.1?,which almost tiled on the sample surface.