Ajay Tripathi

Photoinduced enhanced Raman spectroscopy (PIERS) has emerged as an important extension of surface enhanced Raman spectroscopy (SERS), providing enhanced sensitivity through the synergistic effect of electromagnetic field amplification and photoinduced charge transfer (CT) processes. In a typical PIERS configuration, photoactive semiconductor substrates such as TiO2, ZnO, or WO3 are decorated with plasmonic nanoparticles (NPs) and subjected to UV pre-irradiation, which generates oxygen vacancies and sub-bandgap defect states. These defects facilitate efficient interfacial CT from the semiconductor through the plasmonic nanostructure to the adsorbed analyte, thereby amplifying the Raman scattering cross-section beyond what can be achieved through electromagnetic enhancement alone. This review systematically examines PIERS across four dimensions: (i) the stepwise enhancement mechanism involving defect-mediated UV/photoirradiation and interfacial CT; (ii) substrate architectures spanning noble metal-semiconductor nanocomposites, noble-metal-free defect-engineered platforms, and hybrid systems incorporating MXenes, perovskites, and piezoelectric materials; (iii) excitation parameters, including Raman laser excitation and UV irradiation conditions such as power, wavelength, and duration and (iv) signal stability, oxygen vacancy dynamics, and long-lived PIERS responses arising from Schottky barrier formation at metal-semiconductor interfaces. The review concludes with practical guidelines for benchmarking and standardizing PIERS data to enable meaningful cross-laboratory comparison.

Blue-emitting CS-CDs were derived from mustard oil soot, enabling sensitive Pb ²⁺ detection via PL quenching, efficient pollutant adsorption, and cell imaging. It proves their multifunctional promise in sensing and biomedicine.

P { line-height: 115%; margin-bottom: 0.25cm; background: transparent }Metadynamics using an environment similarity index (compared to perfect bcc) probed Ti’s solid-liquid equilibrium. At 1 atm and 1900 K, free energies of both phases are equal, near the reported melting point of 1918 K. Configurations from the biased trajectory’s saddle were used for unbiased NVE simulations. Committor probability analysis located the transition state, characterized by bond orientational order and Voronoi polyhedra. The transition state contains 22% solid-like atoms: 8% are bcc atoms, staying clustered, while the remaining 14% are distorted bcc/fcc/hcp atoms spread throughout the box.

This study investigates the morphological evolution and enhanced crystallinity of FeMnNiAlSiC high-entropy alloy (HEA) nanoparticles (NPs) synthesized using a picosecond laser operating in burst mode and subsequently processed with a nanosecond laser in deionized water (DW). The initial synthesis via pulsed laser ablation in liquid (PLAL) revealed distinct phases, like B2, γ-brass, Fe₅Si₃, and body-centered cubic (BCC), as confirmed by high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray diffraction (XRD) data. Elemental mapping indicated enrichment of B2-type phases (Al–Fe and Al–Ni) in the larger NPs, while smaller NPs exhibited γ-brass and Fe₅Si₃-type phases. Following nanosecond laser processing, the NPs displayed significant morphological transformations, including the emergence of hollow structures, as well as enhanced crystallinity. Post-processing analysis demonstrated the evolution of B2 and Fe₅Si₃-type phases, driven by a laser-induced annealing effect, which resembles the traditional furnace annealing. This dual-stage laser approach effectively combines the rapid synthesis of NPs with structural refinement, offering a versatile pathway for tailoring material properties. These findings underscore the potential of laser-based techniques in the controlled synthesis and structural modulation of HEA NPs, paving the way for applications in catalysis, energy conversion, and advanced functional materials.

Ag and Au nanoparticles (NP), along with carbon quantum dots (CQD), were synthesized using straightforward methods. Ag NP exhibit localized surface plasmon resonance (LSPR) at 445 nm and Au NP at 551 nm. The quantum yield of as-synthesized CQD in water has been found to be 0.46 at 350 nm excitation. Nanocomposites (Au-CQD, Ag-CQD, Ag–Au, and Ag–Au-CQD) were used as surface enhanced Raman scattering substrates for methylene blue (MB) detection. At 785 nm excitation, Ag-CQD and Ag–Au-CQD showed higher analytical enhancement factors (AEFs) of 1.1 ×104 and 2.5 ×104, respectively, compared to Ag–Au (0.7 ×104). At 514 nm, simultaneous excitation of Ag and Au LSPR improved AEFs, especially for Ag–Au (1.7 ×104) and Ag–Au-CQD (1.8 ×104). Detection limits reached 10−7 M for Au-CQD and 10−8 M for others at 785 nm, while all composites showed a uniform detection limit of 10−8 M at 514 nm. AEFs were reproducible with ∼2%–9% relative standard deviation. Furthermore, COMSOL Multiphysics was used to analyze electric field distribution and establish a strong correlation between theoretical EFs and experimental AEFs in Ag–Au and Ag–Au-CQD nanocomposites. Additionally, photoinduced enhanced Raman scattering (PIERS) studies under 445 nm illumination revealed enhanced Raman signals via photoinduced charge transfer from CQD to metal NP. The highest enhancement was observed in Ag–Au-CQD, followed by Ag-CQD and Au-CQD, while Ag–Au without CQD showed minimal effects. Thus, the dual-wavelength approach enhances PIERS performance for sensitive MB detection.