Study Of The Construction And Property Of Capillary-Based SERS Substrate

Owning to its advantages such as high sensitivity down to single molecular, molecular fingerprint features, nondestructive detection, low consumption of samples and so on, surface-enhanced Raman spectroscopy (SERS) can detect and monitor in real-time, fast and sensitively, which now has been widely used in biology, medicine, analytical chemistry, physical chemistry and so on. But it is still limited when SERS technique is used to analyze in the real world, which mainly because the reproducibility and stability of conventional SERS substrate cannot meet the needs of practical detection. Therefore, in order to improve the reproducibility of the substrates, SERS substrate with uniform hotspots must be designed and constructed. There are a lot of researches on assembly of nanoparticles have been reported. But, several substrates among them need be prepared on strict conditions, with complex methods or expensive, which is not suitable for wide application. To apply SERS technology in widespread field, it is necessary to prepared portable SERS substrate with long shelf life, high sensitivity, good reproducibility and stability in simple and low-cost ways. As a result, this paper aims at constructing capillary-based SERS active substrates by assembling metal nanoparticles onto the inner wall of capillaries. Based on the capillary action, capillaries can act as effected SERS substrate as well as sampling tools. Moreover, for the microenvironment formed by themselves, capillaries can also be used as a microreactor. The details about our researches are summarized as follows:1. First of all, plentiful hydroxyl were modified on the inner wall of cleaned capillaries. Then effect and stable gold nanorods or gold nanodumbbells were synthetized in the widely-used seed growth method and further modified to ensure their surfaces were electronegative. Consequently, for the static force between gold nanostructures and amino groups, gold nanorods or gold nanodumbbells can be easily assembled onto the inner surface of capillaries. Based on the design of experiment, the effect of the concentrations of the nanoparticle suspension as well as their retention time in the capillaries on the assembly were studied. The sensitivity, repeatability, stability and applicability of the obtained gold nanorods and gold nanodumbbells coated capillaries under the condition of the optimization were also investigated and further compared.2. The practicality of caplliary-based substrate was further investigated by involving in the capilliaries coated by gold nanodumbbells as SERS substrate and prohibited colorant as test object. Firstly, in orded to investigate the detection limit, tartrazine, sunset yellow, orange II and chrysoidine with different concentrations were detected using the construted caplliarise as SERS substrate. Then, in consideration of the possibility that the same colour and lustre pigments may be used at the same time, different hybrid system of four pigments were also detected. Finally, to investigate the on-site application of the constructed caplliary-based SERS substrate, four pigment in the orange juice and coke were detected.3. Recently, in situ monitoring the process of organic chemical reactions to understand their mechanisms and kinetics by SERS has been the focus of intense research in the applications of SERS. However, the limitation for application of SERS to monitor of the inorganic reactions exists. Here a new idea in studying inorganic chemical reactions by SERS technique was presented.1,10-phenanthroline (phen) is a rigid planar, hydrophobic, electron-poor heteroaromatic system. These structural features determine its noticeable coordination ability for transition metal cations. For example, 1,10-phenanthroline easily forms in aqueous-solution octahedral complexes of [Fe(phen)3]2+ and [Fe(phen)3]3+ with Fe (II) and Fe(III). It is worth noting that the [Fe(phen)3]3+ can be photoreduced to [Fe(phen)3]2+ in aqueous solution, which need not any catalyst or reductant. As a result, that based on the complex of metal ions with organic ligand 1,10-phenanthroline and subsequent Raman spectrometry to monitor the conversion of Fe3+ to Fe2+ was designed.