Abstract:The efficiency of the generation of Raman spectra by molecules adsorbed on some substrates (or placed at a very close distance to some substrates) may be many orders of magnitude larger than the efficiency of the generation of Raman spectra by molecules that are not adsorbed. This effect is called surface-enhanced Raman scattering (SERS). In the first SERS experiments, nanostructured plasmonic metals have been used as SERS-active materials. Later, other types of SERS-active materials have also been developed. … Show more
“…Therefore, concrete solutions have been proposed to improve the EM enhancement in ZnO nanostructures by combining them with noble metal NPs and tuning the peak location of the LSPR near to the visible region of the EM spectrum and by creating “hot spots” in ZnO ordered nanostructures [ 15 ]. This results in strong scattering and absorption of incident light, thus influencing optical processes such as SEF, SERS [ 16 – 17 ], infrared absorption, and even second harmonic generation [ 18 ], which can improve the performance of optical sensors and optoelectronic devices. ZnO alone and in combination with noble metals has been recently used for the development of SERS substrates [ 15 , 19 ] due to several properties including a high refractive index, which can confine the excitation light in order to enhance the SERS effect, various types of tuneable morphologies that can be used in combination with noble metals, but also its biocompatibility, photocatalytic self-cleaning capability, and high chemical stability, to name just a few.…”
Since the initial discovery of surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF), these techniques have shown huge potential for applications in biomedicine, biotechnology, and optical sensors. Both methods rely on the high electromagnetic fields created at locations on the surface of plasmonic metal nanoparticles, depending on the geometry of the nanoparticles, their surface features, and the specific location of analyte molecules. Lately, ZnO-based nanostructures have been exploited especially as SERS substrates showing high enhancement factors and increased charge transfer effect. Additionally, applications focused on enhancing the fluorescence of analyte molecules as well as on tuning the photoluminescence properties of ZnO nanostructures through combination with metal nanoparticles. This review covers the major recent results of ZnO-based nanostructures used for fluorescence and Raman signal enhancement. The broad range of ZnO and ZnO–metal nanostructures synthesis methods are discussed, highlighting low-cost methods and the recyclability of ZnO-based nanosubstrates. Also, the SERS signal enhancement by ZnO-based nanostructures and the influences of lattice defects on the SERS signal are described. The photoluminescence enhancement of ZnO in the presence of noble metal nanoparticles and the molecular fluorescence enhancement in the presence of ZnO alone and in combination with metal nanoparticles are also reviewed.
“…Therefore, concrete solutions have been proposed to improve the EM enhancement in ZnO nanostructures by combining them with noble metal NPs and tuning the peak location of the LSPR near to the visible region of the EM spectrum and by creating “hot spots” in ZnO ordered nanostructures [ 15 ]. This results in strong scattering and absorption of incident light, thus influencing optical processes such as SEF, SERS [ 16 – 17 ], infrared absorption, and even second harmonic generation [ 18 ], which can improve the performance of optical sensors and optoelectronic devices. ZnO alone and in combination with noble metals has been recently used for the development of SERS substrates [ 15 , 19 ] due to several properties including a high refractive index, which can confine the excitation light in order to enhance the SERS effect, various types of tuneable morphologies that can be used in combination with noble metals, but also its biocompatibility, photocatalytic self-cleaning capability, and high chemical stability, to name just a few.…”
Since the initial discovery of surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF), these techniques have shown huge potential for applications in biomedicine, biotechnology, and optical sensors. Both methods rely on the high electromagnetic fields created at locations on the surface of plasmonic metal nanoparticles, depending on the geometry of the nanoparticles, their surface features, and the specific location of analyte molecules. Lately, ZnO-based nanostructures have been exploited especially as SERS substrates showing high enhancement factors and increased charge transfer effect. Additionally, applications focused on enhancing the fluorescence of analyte molecules as well as on tuning the photoluminescence properties of ZnO nanostructures through combination with metal nanoparticles. This review covers the major recent results of ZnO-based nanostructures used for fluorescence and Raman signal enhancement. The broad range of ZnO and ZnO–metal nanostructures synthesis methods are discussed, highlighting low-cost methods and the recyclability of ZnO-based nanosubstrates. Also, the SERS signal enhancement by ZnO-based nanostructures and the influences of lattice defects on the SERS signal are described. The photoluminescence enhancement of ZnO in the presence of noble metal nanoparticles and the molecular fluorescence enhancement in the presence of ZnO alone and in combination with metal nanoparticles are also reviewed.
“…In this sense, we observe a trend in semiconductors nanoengineering in order to enhance their SERS performance since they may present more stability and allow self-cleaning. To this respect, it is worth mentioning the review by Krajczewski and co-workers [5] where several semiconductors' interesting features have been addressed.…”
Section: Discussionmentioning
confidence: 99%
“…Secondly, when metal nanoparticles (MNPs) are attached to a solid support, they can be placed together in close proximity assuring stability and large enhancements. Thus, nanostructured semiconductors or insulators are used to support plasmonic metals, even paper-based SERS substrates are available [5]. However, one disadvantage of a typical matrix of deposited MNPs is that they cannot be easily reused because the analytes will stay adsorbed on the surface and cause interference.…”
Section: Sers Substrates and Tio 2 /Mnps Arraysmentioning
confidence: 99%
“…SERS measurements can be carried out in solution, by dispersing the analyte molecules in a colloidal metallic solution, or in a solid dry state, by adsorption of the molecules of interest on a SERS substrate. SERS substrates may consist of metal nanoparticles, roughened metallic surfaces, and more recently due to the advances of nanofabrication techniques, of nanoengineered surfaces with metallic nanoparticles deposited on particularly solid support [4,5].…”
As surface-enhanced Raman spectroscopy (SERS) continues developing to be a powerful analytical tool for several probes, four important aspects to make it more accessible have to be addressed: low-cost, reproducibility, high sensibility, and recyclability. Titanium dioxide nanotubes (TiO2 NTs) prepared by anodization have attracted interest in this field because they can be used as safe solid supports to deposit metal nanoparticles to build SERS substrate nanoplatforms that meet these four desired aspects. TiO2 NTs can be easily prepared and, by varying different synthesis parameters, their dimensions and specific features of their morphology can be tuned allowing them to support metal nanoparticles of different sizes that can achieve a regular dispersion on their surface promoting high enhancement factors (EF) and reproducibility. Besides, the TiO2 photocatalytic properties enable the substrate’s self-cleaning property for recyclability. In this review, we discuss the different methodological strategies that have been tested to achieve a high performance of the SERS substrates based on TiO2 NTs as solid support for the three main noble metal nanoparticles mainly studied for this purpose: Ag, Au, and Pt.
“…It is usually effective for a molecule that directly contacts nanostructure surface, especially via chemo-adsorption. Generally, EM mechanism dominates the total enhancement, even for the molecule directly adsorb on nanostructure surface [ [66] , [67] , [68] ]. Fig.…”
Section: Main Metabolic Molecules Detecting Methodsmentioning
Metabolites are important biomarkers in human body fluids, conveying direct information of cellular activities and physical conditions. Metabolite detection has long been a research hotspot in the field of biology and medicine. Surface-enhanced Raman spectroscopy (SERS), based on the molecular “fingerprint” of Raman spectrum and the enormous signal enhancement (down to a single-molecule level) by plasmonic nanomaterials, has proven to be a novel and powerful tool for metabolite detection. SERS provides favorable properties such as ultra-sensitive, label-free, rapid, specific, and non-destructive detection processes. In this review, we summarized the progress in recent 10 years on SERS-based sensing of endogenous metabolites at the cellular level, in tissues, and in biofluids, as well as drug metabolites in biofluids. We made detailed discussions on the challenges and optimization methods of SERS technique in metabolite detection. The combination of SERS with modern biomedical technology were also anticipated.
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