Laser Sintering of TiO2 Films for Flexible Dye-Sensitized Solar Cells

Extremely Sensitive SERS Sensors Based on a Femtosecond Laser-Fabricated Superhydrophobic/-philic Microporous Platform

The detection of molecules from highly diluted solutions with a limited amount is vital for precancer diagnosis, food safety, and forensic analysis. The sensitivity and convenience of detection techniques are the primary concerns. In this study, a hybrid superhydrophobic/-philic (SH/SHL) microporous platform is designed and fabricated by a femtosecond laser to improve surface-enhanced Raman scattering (SERS) performances. Relying on the micropores fabricated at the center of SHL patterns, sediments distributed at the central regions are avoided, leading to the further enrichment of the target molecules. The engineered micropores with high identification further improve the speed of Raman tests, and the fabricated SERS substrate shows an advantage in outdoor handheld detection and automated inspection applications. The optimized SERS sensor is sufficient for attomolar-level detection (10^-17 M) of rhodamine 6G using analyte volumes of just 5 μL, corresponding to an enhancement factor of 5.19 × 10¹³. Meanwhile, a relative standard deviation of 7.48% at 10^-10 M shows the excellent uniformity of this proposed SERS platform. This work further pushes forward the practical applications of SERS technology in ultratrace molecular detections.

Emergence and Evolution of Crystallization in TiO2 Thin Films: A Structural and Morphological Study

Among all transition metal oxides, titanium dioxide (TiO₂) is one of the most intensively investigated materials due to its large range of applications, both in the amorphous and crystalline forms. We have produced amorphous TiO₂ thin films by means of room temperature ion-plasma assisted e-beam deposition, and we have heat-treated the samples to study the onset of crystallization. Herein, we have detailed the earliest stage and the evolution of crystallization, as a function of both the annealing temperature, in the range 250–1000 °C, and the TiO₂ thickness, varying between 5 and 200 nm. We have explored the structural and morphological properties of the as grown and heat-treated samples with Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometry, and Raman spectroscopy. We have observed an increasing crystallization onset temperature as the film thickness is reduced, as well as remarkable differences in the crystallization evolution, depending on the film thickness. Moreover, we have shown a strong cross-talking among the complementary techniques used displaying that also surface imaging can provide distinctive information on material crystallization. Finally, we have also explored the phonon lifetime as a function of the TiO₂ thickness and annealing temperature, both ultimately affecting the degree of crystallinity.