| Gold nanorods have excellent localized surface plasmon resonance(SPR)properties and are widely used in various fields.The preparation method which can easily and accurately control the spectrum and size of gold nanorods,as well as the good application of SPR characteristics,is of great significance for promoting the development of this field.In recent years,research has shown that rods prepared with weakly reducing agents have advantages such as high yield,wide spectral regulation range,and good monodispersity.Rods prepared with strong reducing agents have the characteristic of small diameter.Therefore,the selection of different reducing agent is of great value for the preparation of gold nanorods and for understanding the impact of reducing agent on the growth process of the rods;In addition,small-sized gold nanorods have a wide range of applications in biomedical fields.At present,the commonly used method for preparing small gold nanorods is the seedless method.However,the small gold nanorods prepared by this method have shortcomings such as poor monodispersity,multiple impurities,and narrow control range.It is necessary to improve this method to meet the needs of different sizes;In addition,gold nanorods have two different modes of SPR and are easy to modify.The use of anisotropic modification technology to accurately select the two SPRs of gold nanorods has great potential for promoting the multifunctional application of gold nanorods.Based on this,this paper conducted the following research work:1.Based on the different characteristics of gold nanorods prepared with different reducing agents,this chapter proposes using 1,7-dihydroxynaphthalene with relatively stronger reducibility as a controllable reducing agent for the preparation of gold nanorods.The results showed that the prepared gold nanorods had good monodispersity,high shape yield,relatively small diameter,and a maximum LSPR wave length of over 1000 nm.In addition,by changing the experimental conditions,the LSPR wavelength and diameter of the rod can be accurately controlled.Among them,changing the amount of silver ions or hexadecyltrimethylammonium bromide(CTAB)can increase the wavelength of LSPR from 600 nm to about 1000 nm,and maintain a good linear relationship between the two;Meanwhile,increasing silver ions can reduce the diameter from 28.9 nm to about 14.3 nm,while CTAB can increase the diameter from9.0 nm to about 14.3 nm.Increasing the amount of reducing agent and gold seed can reduce the wavelength of LSPR from 1000 nm to about 800 nm,and the diameter from 14.3 nm to about 9.0nm and 7.3 nm,respectively.2.In order to explore the preparation method of small-sized gold nanorods that are simple and easy to control.In this chapter,a seedless method was used to prepare gold nanorods using1,7-dihydroxynaphthalene as a reducing agent.The results indicate that the prepared gold nanorods have small size,good monodispersity,a diameter of only 11.8 nm when a maximum LSPR wavelength of 1061 nm.By changing the experimental conditions,the LSPR and size of gold nanorods can be controlled.Changing the amount of silver ions can increase the wavelength of LSPR from 588 nm to about 1060 nm,with a minimum diameter of 11.8 nm.By changing the amount of reducing agent,the wavelength of LSPR can be adjusted within 1060-810 nm,and the obtained gold nanorods have a relatively fixed diameter(～11.8 nm)in this range.In addition,by changing the dosage of sodium borohydride,the LSPR of gold nanorods can also be tuned from1060 nm to around 800 nm,with a minimum diameter of 7.2 nm.However,under those conditions,the yield and purity of the gold nanorods are relatively low.3.Based on the significant plasma resonance characteristics,gold nanorods can be used as substrate materials to enhance fluorescence or Raman scattering signals.The selective utilization of the anisotropic SPR of gold nanorods is of great significance for achieving their multifunctional applications.In this chapter,without occupying both ends of the gold nanorod,based on the anisotropic modification of the nanosurface,fluorescence enhancement of Cd Te quantum dots was studied using the uncommonly used transverse plasma TSPR.The effects and characteristics of various conditions on enhanced fluorescence were discussed.The results indicate that increasing the concentration of quantum dots can effectively increase the fluorescence enhancement factor,up to a maximum of about 7 times.At the same time,it was found that compared to fully-coated gold nanorods,anisotropic enhanced structures can achieve similar enhancement effects while also achieving the goal of releasing the two ends structure.In addition,Cd Te quantum dots with different emission wavelengths were selected to discuss the effect of spectral overlap on fluorescence enhancement,indicating that the maximum enhancement effect is achieved when the fluorescence emission wavelength of quantum dots has a relatively large spectral overlap with the TSPR of gold nanorods;The mechanism of enhanced fluorescence was explored,indicating that the SPR of gold nanorods enhances the radiation attenuation rate of Cd Te quantum dots to a certain extent,leading to fluorescence enhancement. |
