Synthesis,fluorescence Functionalization,and Immunoassay Application Of Silica Nanorods

One-dimensional nano-silica has shown great potential in biological detection,cell imaging,and disease treatment,owing to their unique properties of anisotropic structure,high aspect ratio and easy surface functionalization.To date,the advance of one-dimensional nano-silica has still been slow compared with nanospherical silica.There are still some technical barriers in the preparation of one-dimensional silica nanomaterials with controllable morphology,size,and chemical composition,which limit the development and application of one-dimensional nano-silica.To fulfill this need,we developed a simple one-pot emulsion-droplet-based growth method of one-dimensional silica nanorods,in which the reverse phase microemulsion system was constructed by using polyvinylpyrrolidone,sodium citrate,pentanol,and water.Teraethylorthosilicate(TEOS)was used as the silica source and ammonia was used as the catalyst.The aspect ratios and infrared fingerprint signals of the silica nanorods were precisely controlled.We systematically studied the growth mechanism of the silica nanorods.A dual-mode ultrasensitive immunoassay based on the shape code and infrared absorption fingerprint signals of the silica nanorods was realized.Besides,this method was extended to the preparation of fluorescent silica nanorods and achieved the fluorescence functionalization of the silica nanorods.The fluorescent silica nanorods were also used for ultrasensitive immunoassay.The main research contents are as follows:(1)To accurately and easily control aspect ratios and the related characteristics of silica nanorods,we designed and used a one-pot emulsion-droplet-based growth method to prepare silica nanorods under static condition for 4 hours.The aspect ratios of silica nanorods were precisely controlled from 1.0 to 11.6 by tuning the ammonia concentration.Analysis of TEOS consumption rate,conductivity,and Fourier transformation infrared(FTIR)absorption spectra indicated that the aspect ratios and infrared fingerprint signals(the transverse optical and the longitudinal optical phonon modes)of the silica nanorods were dependent on the balance of the hydrolysis and condensation processes.We built a dual-mode sandwich immunoassay based on the shape code and infrared fingerprint signals of the silica nanorods.The shape code of the silica nanorods was used for simple,rapid qualitative,and sensitive semi-quantitative immunoassay by using a conventional optical microscope because of their visibly recognizable shape information.The characteristic infrared absorption fingerprint signals of the silica nanorods allowed for reliable and ultrasensitive quantitative immunoassay with good selectivity and high specificity.The detection limit and the linear range were found out to be 0.5 pM and 1 pM-10 nM,respectively.The research has opened up a new way to promote the industrial production of one-dimensional silica nanomaterials and accelerate its practical process.(2)In order to verify the universality of one-pot emulsion-droplet-based growth method and realize the fluorescence functionalization of silica nanorods,perylenetetracarboxylic dianhydride was used as fluorescent probe because of its high photochemical stability.Perylenetetracarboxylic dianhydride was firstly covalently bound to 3-aminopropyltriethoxysilane by amidation.Then,fluorescent SiO2 nanorods were successfully prepared by one-pot emulsion-droplet-based growth method using TEOS and perylene derivative as the precursor.Perylene had been covalently bound to the silica nanorods to prevent the dyes from leaking out,which led to improving the photostability of perylene.The aspect ratios of the fluorescent silica nanorods can be precisely controlled from 1.0 to 13.4 via the ammonia concentration,reaction time,and reaction temperature.An immunoassay was performed,and the fluorescent signals of the silica nanorods allowed for ultrasensitive quantitative immunoassay with good selectivity,high stability,and high specificity.The detection limit and the linear range were found out to be 0.3 pM and 1 pM-20 nM,respectively.This one-pot emulsion-droplet-based growth method is expected to be used for the preparation of silica nanorods and other related materials.