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The WO3 nanopores array was obtained by an anodization method in aqueous solution with addition of F- ions. Several factors affecting the final morphology of the samples were tested such as potential, time, and F- concentrations. The morphology of the formed nanopores arrays was examined by SEM microscopy. It was found that the optimal time of anodization process is in the range of 0.5-1 h. The nanopores size increased with the increasing potential. The XPS measurements do not show any contamination by F- on the surface, which is common for WOx samples formed by an anodization method. Such a layer was successfully modified by anisotropic gold trisoctahedral NPs of various sizes. The Au NPs were obtained by seed-mediated growth method. The shape and size of Au NPs was analysed by TEM microscopy and optical properties by UV-VIS spectroscopy. It was found that the WO3-Au platform has excellent SERS activity. The R6G molecules could be detected even in the range of 10-9 M.
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Powder bed fusion using a laser beam (PBF-LB) is a commonly used additive manufacturing (3D printing) process for the fabrication of various parts from pure metals and their alloys. This work shows for the first time the possibility of using PBF-LB technology for the production of 3D titanium substrates (Ti 3D) for surface-enhanced Raman scattering (SERS) measurements. Thanks to the specific development of the 3D titanium surface and its nanoscale modification by the formation of TiO2 nanotubes with a diameter of ~80 nm by the anodic oxidation process, very efficient SERS substrates were obtained after deposition of silver nanoparticles (0.02 mg/cm2, magnetron sputtering). The average SERS enhancement factor equal to 1.26 × 106 was determined for pyridine (0.05 M + 0.1 M KCl), as a model adsorbate. The estimated enhancement factor is comparable with the data in the literature, and the substrate produced in this way is characterized by the high stability and repeatability of SERS measurements. The combination of the use of a printed metal substrate with nanofunctionalization opens a new path in the design of SERS substrates for applications in analytical chemistry. Methods such as SEM scanning microscopy, photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD) were used to determine the morphology, structure and chemical composition of the fabricated materials.
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The deposition of a layer of plasmonic metal on a surface of highly ordered nanostructured oxide is one of the important methods of preparation of substrates for surface-enhanced Raman scattering (SERS) measurements. In this contribution we describe formation of SERS substrates by the deposition of a gold layer on ordered ZrO2 nanotubes. The influence of various experimental parameters on the structure of formed composites and the achievable SERS enhancement factor has been analysed. Like commonly used SERS substrates formed by the deposition of plasmonic metals on TiO2 nanotubes, gold-covered ZrO2 nanotubes also could be used as reversible SERS platform after water rinsing: there is no any significant decrease in the SERS activity of the substrate even after 20 radiation-induced cleaning cycles. Moreover, SERS substrates formed on ZrO2 nanotubes are significantly more stable in strongly acidic media than the previously developed SERS substrates based on ordered TiO2 nanotubes.
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In this review article, various methods for the light-induced manipulation of plasmonic nanoobjects are described, and some sample applications of this process are presented. The methods of the photo-induced nanomanipulation analyzed include methods based on: the light-induced isomerization of some compounds attached to the surface of the manipulated object causing formation of electrostatic, host-guest or covalent bonds or other structural changes, the photo-response of a thermo-responsive material attached to the surface of the manipulated nanoparticles, and the photo-catalytic process enhanced by the coupled plasmons in manipulated nanoobjects. Sample applications of the process of the photo-aggregation of plasmonic nanosystems are also presented, including applications in surface-enhanced vibrational spectroscopies, catalysis, chemical analysis, biomedicine, and more. A detailed comparative analysis of the methods that have been applied so far for the light-induced manipulation of nanostructures may be useful for researchers planning to enter this fascinating field.
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Surface-enhanced Raman spectroscopy (SERS) substrates prepared by immobilizing silver cubic nanoparticles (Ag CNPs) on titanium dioxide nanotubes (TiO2 NTs) were used for investigations of the "coffee ring" (CR) effect and its impact on spatial reproducibility of measured Raman signals in comparison with flat surfaces (Ti and Si) where the CR effect is usually significant. The immobilization of nanoparticles from drops, which is a very simple technique, usually does not permit a homogeneous distribution of deposited NPs because there is significant accumulation of the material at the boundary of the drying area. Our proposed SERS substrates effectively reduced the CR effect through the use of well-ordered nanostructures where a smaller number of Ag CNPs were transferred to the boundary region. It was not only the surface morphology that was important but also the physicochemical properties of TiO2 NTs, such as wettability. The wettability of the prepared samples was determined by measuring the static water contact angle (WCA), and the chemical composition near the boundary of the drying area was studied using Auger electron spectroscopy. The morphology of the substrates obtained was characterized using scanning electron microscopy. Our studies showed that reducing the coffee ring effect increased the spatial reproducibility of the measured SERS signal in the area of the deposited CNPs. Therefore, the platforms obtained may be very useful in commercial SERS applications.
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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. In this review article, various SERS substrates formed on nanostructured non-metallic materials, including non-metallic nanostructured thin films or non-metallic nanoparticles covered by plasmonic metals and SERS-active nanomaterials that do not contain plasmonic metals, are described. Significant advances for many important applications of SERS spectroscopy of substrates based on nanostructured non-metallic materials allow us to predict a large increase in the significance of such nanomaterials in the near future. Some future perspectives on the application of SERS substrates utilizing nanostructured non-metallic materials are also presented.
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In this work we show that ordered freestanding titanium oxide nanotubes (TiO2 NT) may be used as substrates for the simple and efficient immobilization of anisotropic plasmonic nanoparticles. This is important because anisotropic plasmonic nanostructures usually give greater spectral enhancement than spherical nanoparticles. The size of the pores in a layer of titanium oxide nanotubes can be easily fitted to the size of many silver plasmonic nanoparticles highly active in SERS (surface-enhanced Raman scattering) spectroscopy (for example, silver nanocubes with an edge length of ca. 45 nm), and hence, the plasmonic nanoparticles deposited can be strongly anchored in such a titanium oxide substrate. The tubular morphology of the TiO2 substrate used allows a specific arrangement of the silver plasmonic nanoparticles that may create many so-called SERS hot spots. The SERS activity of a layer of cubic Ag nanoparticles (AgCNPs) deposited on a tubular TiO2 substrate (AgCNPs@TiO2 NT) is about eight times higher than that of the standard electrochemically nanostructured surface of a silver electrode (produced by oxidation reduction cycling). Furthermore, a super hydrophilic character of the TiO2 nanotubes surface allows for a uniform distribution of AgCNPs, which are deposited from an aqueous suspension. The new AgCNPs@TiO2 NT hybrid layer ensures a good reproducibility of SERS measurements and exhibits a higher temporal stability of the achievable total SERS enhancement factor-one that is far better than standard SERS silver substrates. To characterize the morphology and chemical composition of such evidently improved SERS platforms thus received, we applied microscopic techniques (SEM, and scanning transmission electron microscopy (STEM)) and surface analytical techniques (Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS)).
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OBJECTIVE: To develop our own procedures, allowing for a quick evaluation of glomerular basement membrane (GBM) thickness and to present a statistical classification of thin basement membrane disease (TBMD), minimal change disease (MCD), and IgA nephropathy (IgAN) cases. STUDY DESIGN: Measurements were carried out with the aid of the original software for semiautomatic image analysis on biopsies from 31 children with TBMD, 51 with MCD, and 10 with IgAN. RESULTS: The strongest statistically significant dependence between GBM thickness and age was observed in children with MCD below 5 years of age. There was no significant dependence between GBM thickness and age among patients with TBMD. The values of all analyzed parameters characterizing GBM thickness distribution in children with TBMD were significantly lower than those in patients with MCD and IgAN. A slight, statistically significant increase of some parameters was noted in children with IgAN in contrast to patients with MCD. The multivariate logistic regression model with three independent variables--quartile 1, quartile 3, and percentile 30--proved to be the most appropriate in differentiating between patients with TBMD and children with MCD or IgAN. The model allowed for correctly classifying 96.8% of patients with TBMD (30 of 31 children) and 98.4% patients from the MCD and IgAN groups (60 of 61 children). We failed to construct a similarly appropriate model for differentiating between patients with MCD and IgAN. CONCLUSION: The introduction of morphometric and statistical methods to routine nephropathologic diagnostics represents true progress in very precise and quick assessment of GBM thickness.
