Synergistic Double Laser Beam-boosted Liquid Near Infrared-surface Enhanced Raman Scattering Performance Of Plasmonic Metallic Nanomaterials

Surface-enhanced Raman scattering spectroscopy(SERS)is a highly sensitive specific molecular recognition technology,which has the advantages of high sensitivity,single molecule detection,selective recognition,etc.SERS has attracted great attention since its discovery,which has broad application prospects in environmental pollutant analysis,food science,medical diagnosis and other fields.However,the traditional SERS detection relying on preconcentration has been unable to meet the needs of liquid biopsy of DNA,protein and other macromolecules and in situ detection of chemical reaction processes in the biomedical field.Therefore,the liquid-near infrared(NIR)SERS with high penetrating power,anti-interference,low damage and low signal-to-noise ratio has become an important research direction in the field of biochemical detection.However,low intrinsic low photon absorption conversion efficiency and low photon utilization rate in the near infrared region,as well as extremely high molecular dispersion in the liquid phase leading to insufficient contact between the molecules and the substrate,all reduced the activity of liquid-NIR-SERS.Therefore,the detection of highly sensitive liquid-NIR-SERS also became a challenge.It is generally accepted that the SERS with the increased of Raman signals is mainly dependent on the reasonable construction of highly active microscopic configuration.For example,some noble metal materials and heterogeneous structures with unique local surface plasmonic resonance(LSPR)properties in the near infrared region are synthesized.Some progress has been made in these works.However,these excellent NIR-SERS activities of hybrid nanosubstrates would be obviously suppressed when they are practically applied to aqueous molecular detection in real-word solution.Therefore,relying solely on the construction of active SERS substrates was not enough to realize highly sensitive SERS detection.It is urgent to explore new methods to improve the liquid NIR-SERS activity to meet the growing demand for actual detection.Recently,different from the convenient development of SERS-active substrates,some unusual strategies have been also established by introducing an additional energy field into the SERS system that can effectively optimize the plasmonic resonances of metallic nanomaterials.This can further improve the activity of SERS,which has received widespread attention in the super-sensitive detection.Therefore,we designed a synergistic double laser beam-boosted liquid NIR-SERS technology based on Au/Ag nano-urchins(Au/Ag NUs)substrates,which significantly improved the activity of liquid NIR-SERS by the use of the external laser excited an additional electromagnetic enhancement.In addition,we have done some meaningful application studies to detect a variety of probe molecules.The main research contents of this paper are as follows:1.Synergistic double laser beam-boosted liquid-NIR-SERS based on plasmonic metallic nanomaterials.Based on liquid laser irradiation and chemical reduction,multi-dendritic Au/Ag NUs with abundant "hot spots" was prepared,which showed LSPR response in the NIR region and could be used for the study of dual-beam laser liquid NIR-SERS activity.We have demonstrated the versatile double laser-boosted liquid-NIR-SERS by introducing an extra 808 nm laser beam into the routine 785 nm laser excitation of Au/Ag NUs in solution.On the other hand,we also evaluated the effect of additional laser power on enhancement.The additional EM field formed around Au/Ag NUs can be promoted by increasing 808 nm external laser power(0-1.0 W),providing another significant contribution for further dramatically promoting liquid-NIR-SERS activity.Meanwhile,the optimal double-laser confocal region and selected active plasmonic nanostructures can also provide import roles for maximizing NIR-SERS activity.The optimal candidate enables Raman peak intensities of CV molecules to be dramatically enhanced in solution,reaching approximate～34-fold higher than the single 785 nm SERS apparatus.Based on colloidal Au/Ag NUs,the established unique liquid NIR-SERS is highlighted in the term of well activity,versatility,and sensitivity.These findings are expected to realize ultrasensitive and accurate assessment of various pollutant molecules s in real-world scenarios.2.Application of double laser beam-boosted liquid-NIR-SERS system based on Au/AgNUs.Based on colloidal Au/Ag NUs substrates,the collaborative double-beam laser system proposed in Chapter 2 has excellent liquid NIR-SERS performance.We used the double laser system to realize sensitive detection of multiple types of molecules.Firstly,we evaluated the sensitivity of dual-laser enhanced liquid NIR-SERS system using organic aromatic dyes with strong π-π binding as symbolic molecules.The experimental results show that the dual laser system can realize the ultra-sensitive solution detection of a variety of organic aromatic dye molecules:CV(10-11 M),MB(10-11 M),R6G(10-10 M)and MG(10-10 M)molecules,which provides a reliable method for the accurate identification of organic aromatic dyes in liquid environment.Subsequently,in order to further evaluate the universality and sensitivity of the dual-laser system,we applied it to the sensitive detection of tetracycline hydrochloride and benzyl penicillin sodium molecules of two main antibiotics.The detection limit was as low as 10-9 M,indicating that the dual-laser system has good universality.Moreover,the unique double laser boosted NIR-SERS system can realize the ultra-trace liquid detections of nonadsorptive PAHs such as 10-9 M pyrene,10-7 M anthracene and 10-7 M nitropyrene molecules,respectively.The simultaneous NIR-SERS analyses of these three PAHs show the capabilities of this system for the multiplex detection.Moreover,the practical applicability is successfully verified by ultrasensitive precise assessment of pyrene(10-5 M-10-9 M)molecules in actual lake water samples.Based on colloidal Au/Ag NUs,the double laser-excited liquid phase IR-SERS system has good activity,sensitivity,stability,anti-interference,uniformity,discriminability,reproducibility and practicability.The dual laser system constructed in this paper provides a new idea for the monitoring of various pollutants in the real environment and the in situ analysis of biochemical reactions.