Surface enhanced Raman spectroscopy (SERS) is considered a versatile and multifunctional technique with the ability to detect molecules of different species at very low molar concentration. In this work, hierarchical ZnO microspheres (ZnO MSs) and Ag/ZnO MSs were fabricated and decorated by hydrothermal and photodeposition methods, respectively. For Ag deposition, precursor molar concentration (1.9 and 9.8 mM) and UV irradiation time (5, 15, and 30 min) were evaluated by SEM, TEM, X-ray diffraction and Raman spectroscopy. X-ray diffraction showed a peak at 37.9° corresponding to the (111) plane of Ag, whose intensity increases as precursor concentration and UV irradiation time increases. SEM images confirmed the formation of ZnO MSs (from 2.5 to 4.5 µm) building by radially aligned two-dimensional ZnO nanosheets with thicknesses below 30 nm. The Raman spectra of Ag/ZnO MSs exhibited a vibration mode at 486 cm⁻¹ which can be directly associated to Ag deposition on ZnO MSs surface. The performance of SERS substrate was evaluated using rhodamine 6G. The SERS substrate grown at 9.8 mM during 30 min showed the best SERS activity and the ability to detect methylene blue at 10⁻⁹ M.

Spiky Au-Ag nanostars offer intense plasmonic enhancement due to their sharp-tipped morphology, enabling powerful surface-enhanced Raman scattering (SERS). Here, we report a liquid-phase SERS platform that addresses current limitations in cancer biomarker detection, such as low sensitivity and dependence on Raman reporters. Nanostar concentration was tuned by simple centrifugation (10, 30, and 60 min), and their SERS performance was evaluated using methylene blue (MB) and mercaptopropionic acid (MPA) as probe molecules. Signal intensity scaled with nanostar content, enabling sensitive detection. Optimized nanostars were functionalized with MPA, 1-Ethyl-3-(3-dimethylamino1-Ethyl-3-(3dimethylaminopropyl1) carbodiimide (EDC), and N-Hydroxy succinimide (NHS) for covalent attachment of monoclonal anti-α-fetoprotein antibodies (AFP-Ab), facilitating the detection of AFP antigens across 167–38 ng/mL (antibody) and 500–0 ng/mL (antigen) ranges. The limit of detection (LOD) for the antigens was determined to be 16.73 ng/mL. Unlike conventional SERS systems, this aqueous, surfactant-free platform exploits the intrinsic vibrational modes of AFP, enabling sensitive and rapid biomarker detection with strong potential for early cancer diagnostics.

A surface-enhanced Raman scattering (SERS) substrate based on three-dimensional silver dendrites (AgDs) was developed on bamboo-like TiO₂ nanotubes (BTNTs) fabricated through alternating voltage anodization. The AgDs were grown by short-pulse current electrodeposition, which promoted hierarchical and vertical formation, a process favored by self-formed oxide cracks and axial segmentation in the BTNTs. This fractal 3D architecture results in a high density of hot spots, intensifying the local electric field. Methylene blue was used as the probe molecule, yielding clear Raman signals at concentrations as low as 1 × 10⁻¹⁰ M. The limit of detection was calculated to be 1.6 × 10⁻¹¹ M, with an analytical enhancement factor of 3.0 × 10⁷. This work provides a reproducible, scalable, and cost-effective route to fabricate high-performance SERS substrates in various real applications.

This research shows an experimental study and analysis on microbubbles formation, through the use of chemically modified optical fiber tips. Microbubbles are formed in highly absorbent liquid using a continuous wave laser at 980 nm, with conventional powers. This report is considered, as the first study and dynamic analysis for microbubble formation in solution with these particular types of tips. Fiber tips are modified by the chemical wear method, using hydrofluoric acid, while, microbubbles are generated with the help of the deposition or adhesion of nanostructures on the modified tips. We have used carbon nanotubes dissolved in ethanol as nanostructures. We present an analysis of the results considering: the growth curves of the microbubbles, the largest radii, the lifetime and the growth rate. Finally, we discuss the important features of results, suggesting a possible way to control the size and number of microbubbles. Furthermore, the results of our research could be useful to improve the proposals of earlier applications or to propose new ones. The results shown can be useful for new applications or to improve proposals.

In this work, the effect of the applied current density (J) during galvanostatic anodization of titanium (5–30 mA/cm²) on the TiO₂ morphology and its influence on the SERS performance after pulsed silver electrodeposition (5 mA/cm², 400 cycles, 50 ms ON/250 ms OFF) was evaluated. SEM micrographs showed a transition from nanotubes with scarce nanograss to a dense coverage of nanograss over the surface, which conditioned the formation and distribution of silver nanoparticles and dendrites. Using methylene blue as a probe molecule, the substrate anodized at 15 mA/cm² exhibited the highest SERS intensity, attributed to the high density of hot spots vertically distributed in the 3D dendrites. The optimized substrate demonstrated detection of methylene blue down to 1 × 10⁻¹¹ M and reached an analytical enhancement factor of 7 × 10⁷, highlighting its strong performance. These results establish galvanostatic anodization as a novel and effective route for designing reproducible and scalable TiO₂/Ag substrates with high SERS response.