JLU-PERS Group
Plasmon-enhanced Raman spectroscopy (PERS)@Jilin University
Research Topics
The perspective of PERS group is to build, develop, modify and employ the spectroscopic theories and methods to answer questions in surface science.
Main research contents involve: (1) To design, develop and modify spectroscopic methods and instruments for learning the interaction between molecules, e.g., SPR-SERS co-detection and SERS optical fiber sensor for chemical and bio analysis and detection. (2) Exploring new spectroscopic and experimental methods for self-assembly systems. We developed many high-sensitive techniques, e.g. waveguide-enhanced SERS, directional SERS, plasmonic nanoantennas, to investigate the physical chemical subjects about surface and interface and the mechanism of SERS on metals. (3) Utilizing spectroscopic techniques and theories to study on the relations of structure, function, and molecular interaction in the self-assembly systems and metal colloids. We applied many metal nanoparticle-assembled film for SERS, SEF, textile staining, and antibacteria etc.
A spectrometric instrument was designed and developed to realize the combination of surface-enhanced Raman scattering and surface plasmon resonance (SERS and SPR) techniques for the surface and interface analysis and the bioassembly process monitor. It is composed of three main functional parts: an incident light system, an SPR detection system and a spectroscopic detection system. All these systems are mounted on a two-arm goniometer. The information regarding to the changes in the dielectric constant in SPR curves and the angle-dependent spectra regarding to the information of target analyte’s structures can be simultaneously obtained. This setup is versatile and various angle-resolved spectra can be achieved, such as, Raman/fluorescence, light absorption, reflection, transmission, and photochemical/electrochemical luminescence, etc. Via this SPR-SERS microspectrometer, we studied on many topics including the directional emission of SERS, plasmon-coupled fluorescence, SPR-SERS co-detections, propagating and localized SPR co-enhanced SERS, long-range SPR-enhanced SERS, and plasmonic nanoantennas, etc. This spectroscopy owns significance in the characterization of dynamic process in many assembly systems.
This study was supported by the National Natural Science Foundation of China (NSFC) for Scientific Instrument Grant (20627002), NSFC (20973075), Cultivating Project of Major Project of NSFC (91027010), and National Instrumentation Program (NIP) of the Ministry of Science and Technology of China No. 2011YQ03012408.
Noble metal nanoclusters refer to metal particles with a size smaller than 2 nm, which is comparable to the Fermi wavelength of electrons (the de Broglie wavelength of the electrons at the Fermi level is ~0.5 nm for Ag and Au). In such small sized particles, the continuous density of states breaks up into discrete energy. Therefore, as an intermediate between atoms and nanoparticles, metal nanoclusters exhibit molecule-like properties such as strong fluorescence behaviors. Due to the chemical instability and the high surface energy of silver nanoclusters, they tended to interact with each other and had a natural tendency to aggregate, forming larger nanoparticles. Therefore, a proper stabilizing scaffold or template is thus indispensable. The choices of novel, functional template or stabilizing scaffold have great impact on the properties and the optional application areas of silver nanoclusters.
In this study, we synthesized water-soluble, highly stable fluorescent Ag nanoclusters have been synthesized using a novel core/shell solid polymer nanoparticles as a novel template. The solvent effect on the Ag nanoclusters was studied and the effect of carboxyl groups from the template on the formation of Ag nanoclusters was discussed. These highly stable fluorescent Ag nanoclusters have successfully been applied for bioimaging and chemsensing for copper ions. Furthermore, we combined the luminescent Ag nanoclusters with bulk matrices, such as silk and polymeric fibers, to widen their applications on antibacteria.
Constructing a surface-enhanced Raman scattering (SERS) substrate with high activity, good reproducibility and wide applicability, is one of the important subjects in SERS studies. A lot of theoretical researches have showed that strongly enhanced electromagnetic (EM) field occurs in the interstitial regions of intense field amplification (“hot spots”) between closely coupled nanoparticle (NP) aggregates. Previously, the “hot spot” structures were randomly obtained in the irreversible aggregates of metal colloids. The “hot spots” obtained were uncontrollable. In later studies, controllable “hot spot” construction has been frequently adopted. Here, we demonstrated several methods to fabricate highly efficient SERS substrates based on self-assembly techniques. These structures greatly increase the achievement of “hot spots” and enable a large amplification of SERS signals. Also, the reproducibility has been greatly improved.
This work was supported by the National Natural Science Foundation of China NSFC Grant Nos. 20773045, 20903043 and Research Fund for the Doctoral Program of Higher Education of China Grant No. 20090061120089.
Anisotropic metal nanoparticles with controlled morphologies and well-tuned sizes have wide application in many fields. We developed several methods to synthesize anisotropic silver nanoparticles, such as photo-induced [1-4, 9-10] and heating reduction [5], self-sacrificial template methods.[6, 7] We proposed the wavelength self-limiting effect for the growth of silver nanoparticles in photochemical reaction.[3] Beside the photochemical methods, self-sacrificial template method has been proved to be an effective approach for preparing anisotropic silver nanoparticles. Silver nanodisks and hexagonal nanoplates were prepared through a light-driven Ostwald ripening process[2, 5, 9] or a halide ion etching reaction.[6, 8, 12] Also, we can prepare the nanorings of gold and silver by etching the {111} facets of nanoprisms by HAuCl4. [7, 11]
Moreover, several spectral techniques on analysis of time-resolved LSPR spectroscopy have been developed, such two-dimensional correlation analysis (2D-COS) and principal component analysis (PCA).[12-14] The kinetics process in a nano reaction has been disclosed.[12]
Furthermore, we assembly these anisotropic metal nanoparticles on solid-supported substrates for the applications of surface-enhanced Raman scattering [4, 6, 11, 20-23], LSPR sensing[7, 17, 24], plasmon-enhanced fluorescence [15], coloration of fabric[16,18, 19], and antibacterial [18, `9]etc..
This study was supported by the National Natural Science Foundation of China (NSFC) Grant (20773045 and 20903043), and Research Fund for the Doctoral Program of Higher Education of China (No. 20090061120089)
Nanogeometry of burgeoning nanomaterials has been one of the main focuses of surface plasmon photonics and plasmonic devices. It has been found that within the close proximity of a metal surface lies the magic domain where electromagnetic field is astonishingly enhanced under the illumination of light with a certain wavelength. This enhancement is putatively attributed to the collective oscillations of surface electrons, ie surface plasmons, which can be tuned and thus improved by a rationally designed surface or a three-dimensional plasmonic nanogeometry. We have combined nanosphere lithography (NSL) and thermal deposition of metal to build an unprecedented hierarchically three-dimensional anodic aluminum oxide (AAO) nanopore array for surface-enhanced Raman scattering (SERS), which is mainly dependent on its ability of significant manipulation of localized and propagating surface plasmons. Most possible application based on our template is to fabricate hexagonally aligned nanowires for plasmonic sensing or optics. The three dimensional fabrication of hard porous template with its novel surface and 3D nanostructure is another promising undergoing aspect for the edifice of plasmonic devices.
In addition, a shallow silver nanowell array substrate was developed for guiding surface-enhanced Raman scattering (SERS) due to its tunable surface plasmon character. The spatial pattern of SERS intensity was characterized by three-dimensional angle-resolved Raman spectroscopy, showing that SERS signals were strong and unidirectional in space. It facilitates SERS collection. This nanowell array in analogy to a phase-array antenna is supposed to be an applicable configuration to many systems which require high collection efficiency like single molecule SERS and tip-enhanced Raman spectroscopy.
This work was supported by the National Natural Science Foundation of China NSFC Grant Nos. 21073073.
Surface-enhanced Raman scattering (SERS)-active optical fiber sensors combine the SERS substrate with optical waveguide, which allow the applications for in situ and long-distance SERS detections. Novel design of the SERS-active sensing layer is one of most important subjects in the development of new SERS active optical fiber sensors. The quality of sensing layer results in the sensitivity and selectivity of a SERS-active optical fiber sensor. We developed several approaches to fabricate the SERS-active sensing layer, for example, the vacuum deposited Ag islands, the assembly of metal colloidal nanoparticles, and the laser-induced metal deposition to in situ modify the fiber tip with SERS-active sensing layer. This method has the advantages of rapidity (within several minutes) and easy control. It can achieve effective adjustments on nanoparticle size and localized surface plasmon resonance (LSPR) only by the light irradiation time. Recently, we chose a porous polymer to modify the optical fiber. The porous structure provides a large surface area, which a great deal metal nanoparticles and analytes posit on. More metal nanoparticles supply higher electromagnetic field enhancement, supporting for higher enhancement ability.
This study was supported by the National Natural Science Foundation of China (NSFC) Grant (29975011).