Synthesis Of Novel Near-Infrared Nanomaterials

Near-infrared nanomaterials are widely applied in ultrasonic diagnosis,imaging,optical display and other fields due to their strong tissue penetration,low background fluorescence and high sensitive fluorescence signal,etc.Noble nanomaterials with unique local surface plasmon resonance（LSPR）effect endow them distantive advantages in biomedical fields.As a typical noble nanomaterial,gold nanorods（Au NRs）,are widely used in biomedical diagnosis and therapy because of their superior biocompatibility and adjustable near-infrared absorption wavelength.However,the current methods for synthesizing Au NRs and their composite structures are difficult to achieve precise control on size and aspect ratio and adjustable near-infrared absorption of them,which often results in poor thermal stability,low tissue penetration,low retention time in tissues,and low delivery efficiency.In order to solve the above problems,a series of synthesized strategies for Au NRs and their composites are proposed in this thesis.The main contents are as follows:（1）We propose a growth strategy mediated by ternary surfactants,and accurately synthesize mini-gold nanorods（mini-Au NRs）under the space limitation of micelles.Through the selectivity and dense accumulation of ternary surfactants,the micelle packing parameters（p）are effectively increased,further reduced the free energy of micelles（F）of the growth system.As a result,Au NRs with small diameter,high purity and adjustable plasmonic wavelength are realized.Compared with conventional methods,the purity of mini-Au NRs can be significantly improved to 100%by changing the relative concentration of ternary surfactants.Moreover,by adjusting the concentration of silver nitrate（Ag NO₃）and the relative ratio of ternary surfactants,the diameter of Au NRs can be dynamically controlled at 6,8 and 11 nm.In addition,the aspect ratio can be adjusted to 2.70～7.32 accompanying with the plasmonic wavelength adjusted in the range of 700～1147 nm.This study solved the problem that size and NIR absorption wavelength limitations of traditional approaches and provided an effective strategy for Au NRs to achieve high tissue penetration rate and high thermal stability in biomedicine.（2）We propose a approach to construct core-shell structure of gold nanorods and regulate their“switch”spectral properties.Although the mini-Au NRs obtained in the above work have achieved great NIR absorption performance,it is still challenging to realize the dynamic and accurate regulation on wide-range absorption wavelength and the multi-component integration of Au NRs.Thus,we have precisely regulated the growth modes involving Frank-van der Merwe（FM）,Volmer-Weber（VW）and Ostwald ripening to integrate Au/Ag/Pt multi-component into Au NRs composite nanomaterials.More importantly,the precisely dynamic control of the near-infrared absorption of composite structures from the visible region（450 nm）to the near-infrared second region（1512 nm）could be achieved via regulating the dielectric environment,gap distance and carrier density in the growth system.Firstly,different classes of reducing agents（dopamine dithiocarbamic acid（DDTC）and L-ascorbic acid（AA））were added to the growth solution to complete the homogeneous and heterogeneous deposition of silver ions（Ag⁺）on the surface of Au seeds,and the LSPR absorption spectrum was precisely regulated from the visible region（450 nm）to the second near-infrared region（1412 nm）.Additionally,hexachloroplatinic acid（H₂Pt Cl₆）was introduced into the homogeneous and heterogeneous Au-Ag core-shell growth environment to achieve superior LSPR absorption performance up to～1512 nm.This study solves the challenge of wide and accurate adjustment of the spectrum in the near-infrared region of nanomaterials,and provides an effective strategy to achieve short intra-tissue residence time in biomedicine.（3）We propose a synthesis strategy for achieving janus structure of polymer functionalized gold nanorod,which uses polymer ligands to regulate the interfacial energy between metals.In our second work,although the multi-component optical performance integration was realized,the optical performance can not be amplified due to the large difference in the environmental exposure degree of the surfaces of different components.Therefore,in this chapter,we continuously regulate the surface energy of gold by changing the amount of deposited metal and the hydrocarbon chain length of sulfhydryl-polystyrene（SH-PEG）molecules,and obtain a series of janus nanostructures.This work can realize the amplification of the optical properties of the nanostructures while regulating their near-infrared absorption,provides an effective strategy for achieving efficient delivery efficiency in the biomedical field.In summary,this thesis proposes three kinds of growth strategies of gold nanorods and their composite structures to construct a new type of near-infrared noble metal nanomaterials,to achieve accurate and adjustable size,aspect ratio,composition and morphology,and to achieve dynamic and accurate and controllable near-infrared spectral properties,which lays a foundation for expanding its applications in sensing detection,biomedicine and optical display.