Search

A bipartite system is defined as two microscopic entities being able to exchange energy. When excited by light, the complete optical response functions at first (polarizabilities) and second orders (first hyperpolarizabilities) of such a system are determined using the diagrammatic theory of optics. The generality of the method is ensured by the free choice of light–matter and matter–matter interaction Hamiltonians and by the arbitrary number of quanta involved in the energy exchange. In the dipolar approximation, the optical response functions of the system (i.e., of the interacting entities) are linked to the responses of the interaction-free entities by transfer matrices. These universal matrices identically modify the optical response functions at all orders in the electromagnetic field, allowing the implementation of matter–matter interactions in higher-order processes, such as stimulated or spontaneous Raman scattering and four-wave mixing. This formalism is then applied to various composite systems: dimers, multimers and lattices of nanoparticles and molecules, dense molecular layers, and substrate-induced image dipoles. [ABSTRACT FROM AUTHOR]

Computational modeling of plasmon-mediated molecular photophysical and photochemical behaviors can help us better understand and tune the bound molecular properties and reactivity and make better decisions to design and control nanostructures. However, computational investigations of coupled plasmon–molecule systems are challenging due to the lack of accurate and efficient protocols to simulate these systems. Here, we present a hybrid scheme by combining the real-time time-dependent density functional theory (RT-TDDFT) approach with the time-domain frequency dependent fluctuating charge (TD-ωFQ) model. At first, we transform ωFQ in the frequency-domain, an atomistic electromagnetic model for the plasmonic response of plasmonic metal nanoparticles (PMNPs), into the time-domain and derive its equation-of-motion formulation. The TD-ωFQ introduces the nonequilibrium plasmonic response of PMNPs and atomistic interactions to the electronic excitation of the quantum mechanical (QM) region. Then, we combine TD-ωFQ with RT-TDDFT. The derived RT-TDDFT/TD-ωFQ scheme allows us to effectively simulate the plasmon-mediated "real-time" electronic dynamics and even the coupled electron–nuclear dynamics by combining them with the nuclear dynamics approaches. As a first application of the RT-TDDFT/TD-ωFQ method, we study the nonradiative decay rate and plasmon-enhanced absorption spectra of two small molecules in the proximity of sodium MNPs. Thanks to the atomistic nature of the ωFQ model, the edge effect of MNP on absorption enhancement has also been investigated and unveiled. [ABSTRACT FROM AUTHOR]

Indium selenide is a polymorphous material system that has attracted considerable attention due to the outstanding electronic, optical, ferroelectric, and antiferroelectric properties of its various crystalline phases; however, this polymorphism adds a layer of complexity to the analysis of Raman and x-ray photoelectron (XPS) data of these materials. In this report, a method of quantitative analysis of combined Raman and XPS data is developed to determine the stoichiometry of indium selenide thin films, as well as the phase fraction of β-In2Se3, γ-In2Se3, and κ-In2Se3 within the films. A 13:1 ratio of the indium to selenium sensitivity factors (σIn/σSe = 13) was found to yield the most accurate stoichiometry results. Further structural characterization of the κ-In2Se3 film was performed and points to its existence in these films as a distinct phase, rather than strained γ-In2Se3. [ABSTRACT FROM AUTHOR]

This paper explores the unintentional contamination of Surface-Enhanced Raman Scattering (SERS) substrates by ambient hydrocarbon contaminants and their contribution to SERS spectra. Previous studies have identified amorphous carbon as a potential complicating factor in data analysis in SERS experiments, although its origin has been elusive. Our work showed that ambient hydrocarbon contamination and its decomposition products can be detected by SERS on a gold substrate. We propose that ambient air itself is a source of amorphous carbon contamination on SERS substrates. This understanding is crucial for the correct interpretation of SERS data and highlights the need for careful consideration of potential environmental contaminants in SERS analysis. [ABSTRACT FROM AUTHOR]

The rotational relaxation behavior of D2(1,12) in a D2–N2 mixture was investigated using coherent anti-Stokes Raman scattering (CARS) technique. The rovibrational level v = 1 and J = 12 of D2 was selectively excited through stimulated Raman pumping while monitoring the temporal evolution of population for D2(1, J ≤ 12) molecules using time-resolved CARS spectroscopy. The results demonstrate that the rotational relaxation processes of D2(1,12) encompass both multi-quantum relaxation and continuous single-quantum relaxation. When α, the molar ratio of N2, is less than 0.5, D2(1,12) predominantly undergoes a single quantum relaxation process transition. However, when α ≥ 0.5, the multi-quantum relaxation mechanism gradually predominates. The total rotational relaxation rate coefficients of D2(1,12) collisions with N2 and D2 at 295 K were determined to be 3.974 × 10−14 and 1.179 × 10−14 cm3 s−1, respectively. The temperature dependence of rotational relaxation rate of D2(1,12) was investigated within the temperature range of 295–453 K. With increasing temperature, the dominant relaxation process exhibited an accelerated behavior, while the minor relaxation process remained largely unaffected. The rotational temperature of the D2 molecule at various N2 molar ratios was determined through the utilization of Boltzmann plots. The rotational temperature undergoes a rapid decline within 2 μs, corresponding to the near-resonant rotation–vibration relaxation process of D2(1,12) collisions with N2. The system reaches a quasi-equilibrium state when the delay time is 3 μs. The findings of this study can serve as a valuable empirical basis for further validation of the kinetic theory and simulation. [ABSTRACT FROM AUTHOR]

Both spontaneous Raman scattering and stimulated Raman scattering (SRS) are cornerstones of modern photonics, spectroscopy, and imaging. However, a unified understanding of the ultimate detectability of Raman scattering is lacking, due to both historical and technical reasons. Starting from quantum electrodynamics, we formulate the fundamental detectability for both spontaneous Raman scattering and SRS. The key concept is recognizing spontaneous Raman scattering as stimulated Raman process driven by vacuum field fluctuation. A simple and unified expression, Eq. (17), is derived, which can be depicted on a two-dimensional phase-diagram-like graph with inherent symmetry. It turns out that the particle nature of light dictates the ultimate detectability of spontaneous Raman scattering, which can be represented by a line on this detectability diagram. Importantly, if provided with a reasonably strong Stokes photon flux, SRS can breach this fundamental limit and open uncharted territory of drastically accelerated measurement speed and much lower detection concentration relevant to biological imaging. Such new territory in the detectability diagram is otherwise forbidden by the spontaneous counterpart. Diagrammatical analysis explains the empirical observations, provides quantitative insights, and makes new predictions. Notably, recent experimental applications of SRS microscopy can almost entirely be captured by this diagram, further supporting the explanatory power of the theory. Thus, this unified diagrammatic approach outlines a framework to understand all Raman-based measurement and provides a theoretical explanation for the remarkable utility of the emerging SRS microscopy. [ABSTRACT FROM AUTHOR]

The surface-enhanced Raman scattering (SERS) technique provides outstanding molecular fingerprint identification and high sensitivity of analytes. Herein, colloidal sphere-shaped gold nanoparticles (Au-NPs) trapped in concentric rings of the Bessel beam generated from the optical fiber-based negative axicon has been reported as a SERS substrate. With the trapping of Au-NPs, the SERS ability of colloidal Au-NPs improved, and the average enhancement factor (AEF) of the rhodamine-6G (R6G) and 4-aminothiophenol (4-ATP) molecules can reach up to the order of 107. Control experiments were also carried out with the trapping of Au-NPs by Gaussian beam illumination, without any illumination of the light and with the trapping of Au-NPs by the Bessel beam illumination on a silver (Ag)-coated silicon (Si) substrate with a self-assembled monolayer (SAM) of 4-ATP. Theoretical studies were also carried out using the finite element method (FEM) to identify the hotspots generated in the gaps formed between the Au-NPs, leading to an enhancement in the SERS signal of the molecules, and the results were consistent with the experimentally determined AEFs. The obtained results demonstrate that the proposed SERS technique is stable. This study has significant potential applications in clinical diagnosis, food safety, environment safety, chemical sensing, and biosensing. [ABSTRACT FROM AUTHOR]

The terminal alkyne C≡C stretch has a large Raman scattering cross section in the "silent" region for biomolecules. This has led to many Raman tag and probe studies using this moiety to study biomolecular systems. A computational investigation of these systems is vital to aid in the interpretation of these results. In this work, we develop a method for computing terminal alkyne vibrational frequencies and isotropic transition polarizabilities that can easily and accurately be applied to any terminal alkyne molecule. We apply the discrete variable representation method to a localized version of the C≡C stretch normal mode. The errors of (1) vibrational localization to the terminal alkyne moiety, (2) anharmonic normal mode isolation, and (3) discretization of the Born–Oppenheimer potential energy surface are quantified and found to be generally small and cancel each other. This results in a method with low error compared to other anharmonic vibrational methods like second-order vibrational perturbation theory and to experiments. Several density functionals are tested using the method, and TPSS-D3, an inexpensive nonempirical density functional with dispersion corrections, is found to perform surprisingly well. Diffuse basis functions are found to be important for the accuracy of computed frequencies. Finally, the computation of vibrational properties like isotropic transition polarizabilities and the universality of the localized normal mode for terminal alkynes are demonstrated. [ABSTRACT FROM AUTHOR]

We developed a spectroscopic method for directly obtaining the spectra of electromagnetic (EM) enhancement of plasmonic hotspots (HSs). The method was applied to one-dimensional (1D) HSs generated between silver nanowire (NW) dimers. The EM enhancement spectra were derived by dividing the spectra of surface-enhanced fluorescence (SEF) from single NW dimers with SEF obtained from large nanoparticle aggregates, where aggregate-by-aggregate variations in the SEF spectra were averaged out. Some NW dimers were found to exhibit EM enhancement spectra that deviated from the plasmon resonance Rayleigh scattering spectra, indicating that their EM enhancement was not generated by superradiant plasmons. These experimental results were examined by numerical calculation based on the EM mechanism by varying the morphology of NW dimers. The calculations reproduced the spectral deviations as the NW diameter dependence of EM enhancement. Phase analysis of the enhanced EM near-fields along the 1D HSs revealed that the dipole–quadrupole coupled plasmon, which is a subradiant mode, mainly generates EM enhancement for dimers with NW diameters larger than ∼80 nm, which was consistent with scanning electron microscopic measurements. [ABSTRACT FROM AUTHOR]

For large plasmonic nanoparticles, retardation effects become important once their length becomes comparable to the wavelength of light. However, most models do not incorporate retardation effects due to the high computational cost of solving for the optical properties of large atomistic electrodynamics systems. In this work, we derive and implement a recursive fast multipole method (FMM) in Cartesian coordinates that includes retardation effects. In this method, higher-order electrodynamic interaction tensors used for the FMM are calculated recursively, thus greatly reducing the implementation complexity of the model. This method allows for solving of the optical properties of large atomistic nanoparticles with controlled accuracy; in practice, taking the expansion to the fifth order provides a good balance of accuracy and computational time. Finally, we study the effects retardation has on the near- and far-field properties of large plasmonic nanoparticles with over a million atoms using this method. We specifically focus on nanorods and their dimers, which are known to generate highly confined fields in their junctions. In the future, this method can be applied to simulations in which accurate near-field properties are required, such as surface-enhanced Raman scattering. [ABSTRACT FROM AUTHOR]

Understanding the influence of a crowded intracellular environment on the structure and solvation of DNA functionalized gold nanoparticles (ss-DNA AuNP) is necessary for designing applications in nanomedicine. In this study, the effect of single (Gly, Ser, Lys) and mixture of amino acids (Gly+Ser, Gly+Lys, Ser+Lys) at crowded concentrations is examined on the structure of the ss-DNA AuNP using molecular dynamics simulations. Using the structural estimators such as pair correlation functions and ligand shell positional fluctuations, the solvation entropy is estimated. Combining the AuNP–solvent interaction energy with the solvation entropy estimates, the free energy of solvation of the AuNP in crowded solutions is computed. The solvation entropy favours the solvation free energy which becomes more favourable for larger effective size of AuNP in crowded solutions relative to that in water. The effective size of AuNP depends on the different propensity of the crowders to adsorb on Au surface, with the smallest crowder (Gly) having the highest propensity inducing the least effective AuNP size as compared to other single crowder solutions. In mixed crowded solutions of amino acids of variable size and chemistry, distinctive local adsorption of the crowders on the gold surface is observed that controls the additive or non-additive crowding effects which govern an increase (in Gly+Ser) or decrease (in Gly+Lys) in nanoparticle effective size respectively. The results shed light into the fundamental understanding of the influence of intracellular crowding on structure of ss-DNA AuNP and plausible employability of crowding as a tool to design programmable self-assembly of functionalized nanoparticles. [ABSTRACT FROM AUTHOR]

Inelastic scattering between gas molecules and surfaces is a fundamental process that has been investigated extensively. In recent gas-surface scattering experiments [Phys. Chem. Chem. Phys. 19, 19904 (2017)] on formaldehyde scattering off the gold surface, the scattered formaldehyde molecules had a high propensity to excite twirling motion about the C–O bond. In the work presented here, we used classical dynamics simulations to understand energy transfer in formaldehyde–surface collisions and to probe the mechanism of interconversion of translational energy to rotational energy. The simulations reveal an increase in the rotational energy distribution with an increase in collision energies and a preferential rotational excitation about the C–O bond consistent with the experiments. The high propensity to excite the twirling motion was found to arise from a steering motion about the C–O bond during the scattering process governed by the minimum energy path. [ABSTRACT FROM AUTHOR]

Optical metamaterials, sensing, nonlinear optics, and surface-enhanced spectroscopies have witnessed the remarkable potential of the anapole mode. While dielectric particles with a high refractive index have garnered significant attention in recent years, the exploration of plasmonic anapole modes with intense localized electric field enhancements in the visible frequency range remains limited. In this study, we present a theoretical investigation on the relationship between the strongest near-field response and magnetic anapole modes, along with their substantial enhancement of Raman signals from probing molecules. These captivating findings arise from the design of a practical metallic oblate spheroid–film plasmonic system that generates magnetic anapole resonances at frequencies within the visible–near-infrared range. This research not only sheds light on the underlying mechanisms in a wide range of plasmon-enhanced spectroscopies but also paves the way for innovative nano-device designs. [ABSTRACT FROM AUTHOR]

Forward stimulated Raman scattering and backward stimulated Raman scattering (BSRS) are measured when an intense 532 nm nanosecond pulsed laser is focused into water and heavy water. The investigation reveals a significant observation: the formation of the ice VII structure exclusively occurs in the backward direction when optical breakdown takes place, provided that the input energy falls below 90 mJ for liquid water or 75 mJ for heavy water. This phase transition is attributed to secondary shock compression, which comes from energy transfer and compression between the BSRS in plasmas with the pump laser. The optical breakdown experiment under pre-pressure reveals that the shock compression in the back direction is approximately 2.3 times that of the forward direction. This research is useful for shock compression and dynamics in plasmas. [ABSTRACT FROM AUTHOR]

Since it was first predicted 100 years ago, Raman scattering has been a cornerstone of molecular spectroscopy with a widespread impact on science and technology. Nearly all theoretical frameworks have employed Raman cross sections (σRaman) to characterize and quantify molecular Raman response. The recently introduced absolute stimulated Raman scattering cross section (σSRS), on the other hand, provides an alternative way of interpreting molecular responses under two coherent laser sources. However, the theoretical connection between σRaman and σSRS remains unclear. Herein, we are inspired by Einstein's A and B coefficients for spontaneous and stimulated emissions and derived an analogous equation [Eq. (16)] for Raman scattering from an approach along quantum electrodynamics. Equation (16) decomposes Raman cross sections into a contribution from the vacuum electromagnetic field and an underlying molecular response captured by stimulated Raman cross sections (in the unit of Göppert–Mayer). This theoretical relation is supported by recent experimental measurements on methanol as a model compound. Foremost, it provides a connection between experimentally defined σRaman and σSRS under certain approximations. In addition, it quantitatively shows that it is the weak vacuum field of the Stokes channel that makes Raman cross sections appear so small, corroborating the conventional Raman theory. Moreover, it suggests stimulated Raman cross sections to be a vacuum-decoupled intrinsic quantity for characterizing molecular response during Raman scattering. Remarkably, stimulated Raman cross sections turn out to be not weak when compared to two-photon absorption, narrowing the conventional gap of cross sections between spontaneous Raman and UV–vis absorption by more than 1010 folds. [ABSTRACT FROM AUTHOR]

The present investigation involves the in situ growth of Ag nanostructures (NSs) onto a rough Cu surface, accomplished through a cost-effective and straightforward fabrication process. The inherent characteristics of the Cu surface contribute to a certain degree of a surface-enhanced Raman spectroscopy (SERS) signal. Upon integration with Ag NSs, the Cu surface serves as an exceptionally sensitive and consistently uniform substrate for surface-enhanced Raman spectroscopy. Notably, a singular substrate accommodates the simultaneous detection of four distinct probe molecules. Subsequent SERS analyses of Ag NSs on Cu were executed under varying laser power conditions. Intriguingly, despite the escalation in laser power, no substantial shifts were discerned in the peak positions corresponding to the probe molecules. Consequently, it can be inferred that, for investigations where peak position shifts hold significance, the utilization of a thermally conductive material in fabricating SERS-active substrates could confer notable advantages. [ABSTRACT FROM AUTHOR]

Vibrational strong coupling results from the interaction between optically allowed molecular vibrational excitations and the resonant mode of an infrared cavity. Strong coupling leads to the formation of hybrid states, known as vibrational polaritons, which are readily observed in transmission measurements and a manifold of the reservoir states. In contrast, Raman spectroscopy of vibrational polaritons is elusive and has recently been the focus of both theoretical and experimental investigations. Because Raman measurements are frequently performed with high-numerical aperture excitation/collection optics, the angular dispersion of the strongly coupled system must be carefully considered. Herein, we experimentally investigated vibrational polaritons involving dispersive collective lattice resonances of infrared antenna arrays. Despite clear indications of the strong coupling to vibrational excitations in the transmission spectrum; we found that Raman spectra do not bear signatures of the polaritonic transitions. Detailed measurements indicate that the disappearance of the Raman signal is not due to the polariton dispersion in our samples. On the other hand, the Tavis–Cummings–Holstein model that we employed to interpret our results suggests that the ratio of the Raman transition strengths between the reservoir and the polariton states scales according to the number of strongly coupled molecules. Because the vibrational transitions are relatively weak, the number of molecules required to achieve strong coupling conditions is about 109 per unit cell of the array of infrared antennas. Therefore, the scaling predicted by the Tavis–Cummings–Holstein model can explain the absence of the polariton signatures in spontaneous Raman scattering experiments. [ABSTRACT FROM AUTHOR]

Experimental and simulation studies were conducted for surface segregation-limited kinetics of nitrogen incorporation into a 4H-SiC crystal during physical vapor transport (PVT) crystal growth. It was revealed that the nitrogen incorporation is kinetically limited by the step-flow velocity on the growing crystal surface of a 4H-SiC crystal; in this study, the surface step-flow velocity at the growth front was deduced from the local inclination angle of the growth front measured from the (000 1 ¯) plane, assuming a uniform growth rate along the c-axis (crystal growth direction) across the growth front, and the nitrogen concentration across the growth front was measured using Raman scattering microscopy. The step-flow velocity dependence of nitrogen incorporation was theoretically analyzed using a two-site-exchange model, and the simulated dependence using the model was in good agreement with the experimental data. On the basis of these experimental and simulation results, kinematical and energetical aspects of nitrogen incorporation at the growth front of a 4H-SiC crystal during PVT growth are discussed. [ABSTRACT FROM AUTHOR]

The relationship between the electromagnetic (EM) enhancement of the optical responses of molecules and plasmon resonance has been investigated using Rayleigh scattering or the extinction spectra of plasmonic systems coupled with molecular excitons. However, quantum optics predicts that the EM enhancement of such optical responses, e.g., fluorescence, Raman, and their nonlinear counterparts, is related directly to optical absorption and indirectly to Rayleigh scattering and extinction. To demonstrate this prediction, a micro-spectroscopic method for obtaining Rayleigh scattering, extinction, absorption, and EM enhancement is developed using single-coupled plasmonic systems composed of silver nanoparticle dimers and dye molecules. The EM enhancement is derived from ultrafast surface-enhanced fluorescence. An evaluation of the spectral relationships demonstrates that the EM enhancement can be reproduced better by absorption than by Rayleigh scattering or extinction. This reproduction is phenomenologically confirmed by numerical calculations based on classical electromagnetism, indicating the importance of absorption spectroscopy in coupled plasmonic systems for evaluating EM enhancement. [ABSTRACT FROM AUTHOR]

Based on a linearization approximation coupled with path integral formalism, we propose a method derived from the propagation of quasi-classical trajectories to simulate resonance Raman spectra. This method is based on ground state sampling followed by an ensemble of trajectories on the mean surface between the ground and excited states. The method was tested on three models and compared to a quantum mechanics solution based on a sum-over-states approach: harmonic and anharmonic oscillators and the HOCl molecule (hypochlorous acid). The method proposed is able to correctly characterize resonance Raman scattering and enhancement, including the description of overtones and combination bands. The absorption spectrum is obtained at the same time, and the vibrational fine structure can be reproduced for long excited state relaxation times. The method can also be applied to dissociating excited states (as is the case for HOCl). [ABSTRACT FROM AUTHOR]

The accurate measurement of the thermal conductivity in a wide range of semiconductors is of great importance for applications like power electronic devices, which is, however, quite challenging. Current measurement methods suffer from limited measurement range, non-accuracy, complexity, etc. We report in this work an effective in situ method for thermal conductivity measurement based on laser-excited Raman spectroscopy, which has the advantages of non-contact, non-destructive, facile preparation, easy operation, and the capability of a large measurement range. The critical relationship parameters correlating Raman peak shifts and temperature change can be extracted by monitoring and fitting the Raman peak movement at different temperatures. Here, the laser with the micrometer scale spot serves as a Raman scattering source and a heat source for the samples. The thermal conductivity of Si, SiC, polycrystalline diamond, and single crystalline diamond at room temperature was determined to be 140.2 ± 14.4, 414.7 ± 26.2, 1372.3 ± 229.0, and 1734.9 ± 280.6 W/(m K), respectively, which are in good agreement with the theoretical prediction. The temperature distribution of the samples was simulated by the finite element method, which confirms the experimental data. These results highlight the feasibility, reliability, and versatility of Raman spectroscopy for measuring semiconductor materials, particularly those with high thermal conductivity. This is of great interest for exploring semiconductor physics and practical applications like power electronic devices. [ABSTRACT FROM AUTHOR]

We present a Raman scattering spectroscopic study of boron imidazolate metal-organic frameworks (BIFs) with three different magnetic metal ions and one non-magnetic in a wide frequency range from 25 to 1700 cm−1, which covers local vibrations of the imidazolate linkers as well as collective lattice vibrations. We show that the spectral region above 800 cm−1 belongs to the local vibrations of the linkers, which have the same frequencies for the studied BIFs without any dependence on the structure of the BIFs and are easily interpreted based on the spectra of imidazolate linkers. In contrast, collective lattice vibrations, observed below 100 cm−1, show a distinction between cage and two-dimensional BIFs structures, with a weak dependence on the metal node. We identify the range of vibrations around 200 cm−1, which are distinct for each metal-organic framework, depending on a metal node. Our work demonstrates the energy hierarchy in the vibrational response of BIFs. [ABSTRACT FROM AUTHOR]

We report on the metrological characterization of the emission from a germanium-vacancy center in diamond under a microfabricated solid immersion lens in a confocal laser-scanning microscope setup. Ge ions were implanted into a synthetic diamond at 3 MeV, and germanium-vacancy centers were then formed by subsequent annealing. Afterward, solid immersion lenses were fabricated in a focused ion beam scanning electron microscope. The photoluminescence was investigated at room temperature in terms of the spectral distribution, the excited state lifetime, the second-order correlation function, and the saturation behavior, proving simultaneous high single-photon purity and high brightness. Two methods were exploited to minimize the residual multi-photon probability: spectral filtering and temporal filtering. According to these results, we assume that Raman scattered photons and emission from neighboring color centers play an important role in the residual multi-photon emission probability. The system efficiency of the single-photon source was investigated and found to be in accordance with the value calculated from all sources of loss in the setup. The branching ratio of the germanium-vacancy center for the decay into the ground state and into metastable state was calculated. The results enable the usage of the single-photon source in future quantum radiometric experiments. [ABSTRACT FROM AUTHOR]

In recent years, metal-organic frameworks, in general, and zeolitic imidazolate frameworks, in special, had become popular due to their large surface area, pore homogeneity, and easy preparation and integration with plasmonic nanoparticles to produce optical sensors. Herein, we summarize the late advances in the use of these hybrid composites in the field of surface-enhanced Raman scattering and their future perspectives. [ABSTRACT FROM AUTHOR]

In this study, near- and off-resonance Raman spectra of cadmium sulfide (CdS) quantum rods (NRs) and 4-mercaptobenzoic acid (4-MBA) adsorbed CdS NRs are reported. The envelopes of characteristic optical phonon modes in the near-resonance Raman spectrum of CdS NRs are deconvoluted by following the phonon confinement model. As compared with off-resonant Raman spectra, optical phonon modes scattering cross section is amplified significantly in near-resonance Raman spectra through the Fröhlich interaction. The Huang–Rhys factor defining the strength of the Fröhlich interaction is estimated (∼0.468). Moreover, the adsorption of different concentrations of 4-mercaptobenzoic acid (4-MBA) onto CdS NRs produces surface strain in CdS NRs originating due to surface reconstruction and consequently blue and red shifts in off-resonance (514.5 nm) Raman spectra depending on the concentration of 4-MBA. These consequences are attributed to compressive and tensile strains, respectively. Relative to bulk CdS powder as the reference, strain in CdS NRs increases with decreasing 4-MBA concentrations. In off-resonance Raman spectra of 4-MBA adsorbed CdS NRs, the full width at half maxima of phonon modes (1-LO and 2-LO) and intensity ratio I2-LO/I1-LO increase with decreasing 4-MBA concentration. [ABSTRACT FROM AUTHOR]

Controllable tuning of electron–phonon coupling strength and excited state dynamics is important for the understanding of resonance Raman scattering in low-dimensional semiconductors. Here, we report a significant and reversible field-induced modulation in absolute resonance Raman intensity of quantum dots using ionic liquid gating. Meanwhile, a potential-dependent nonlinear relationship is present between Raman intensity and excitation power density. By exploring the parameter space within a time domain model, we find that the Raman intensity variation is mainly determined by the homogeneous linewidth. We further propose that the Fermi level positions and exciton species play key roles in the excited state decay rates. [ABSTRACT FROM AUTHOR]

In this work, a novel study of the feasibility of shared Power over Fiber (PoF) and Fifth‐Generation (5G) New Radio (NR) Analog Radio over Fiber (ARoF) over long distance Hollow‐core Fibers (HCF) is presented. Comparative measurements between similar lengths of HCFs, Multicore (MCF) and Single Mode Fibers (SMF) are performed. A complete analysis on the Stimulated Raman Scattering (SRS)‐induced noise transfer from PoF to ARoF is tackled. Relative Intensity Noise (RIN) of ARoF signals is measured for all the optical fibers tested, observing no degradation in HCFs, neither on MCFs and significant deterioration in SMFs. A combination of PoF and 5G NR ARoF link in a single fiber is implemented, and 5G NR signals with different modulation formats are successfully transmitted through HCFs and MCFs without degradation, while SRS‐induced noise transfer in SMFs massively deteriorate them. PoF transmission efficiencies are also analyzed, achieving up to 9.9 % System Energy Efficiency (SEE) for a 3.1 km HCF, 0.9 % for a 11.1 km HCF and 1.5 %, 13.5 %, and 20.4 % in a 10 km MCF, a 9.8 km SMF and a 3.3 km SMF, respectively. The PoF signal is used to supply a Bluetooth Low‐Energy (BLE) load with a power consumption of ≈$\approx$ 20 mW. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNP) have shown great potential in biomedical applications due to their unique and tunable properties. Understanding the ligand conformation on AuNP has profound interest in nanoparticle research leading to a precise drug delivery system. Colloidal AuNPs were synthesized using trisodium citrate as reducing agent. Normal Raman spectrum (NRS) in solid and aqueous phase identifies that 5‐amino‐2‐mercaptobenzimidazole (5A2MBI) mainly exist as thione form. Surface enhanced Raman scattering (SERS) investigation of 5A2MBI depending on pH was performed to explore the adsorption mechanism of thiolate and thione conformations on AuNPs. Density functional theory (DFT) calculations were used to find the band assignments and molecular electrostatic potential (MEP) mapping to identify the electron rich site where metal can interact preferentially. Using SERS spectral analysis and DFT results, surface adsorption scheme was proposed. At basic pH, 5A2MBI adsorbs on AuNP as thiolate form bidentately via Sulfur and nitrogen atom of imidazole ring with tilted geometry. However, in acidic condition the thione form adsorbs on nanosurface with perpendicular orientation. [ABSTRACT FROM AUTHOR]

The Raman spectra of ferrocene crystals were measured at pressures up to 20 GPa, and an abnormally large bandwidth of intermolecular phonons at ambient pressure was found. With an increase in the pressure, the bandwidth increased to a maximum at ~2 GPa and then decreased to a minimum at ~4 GPa, which was equal to the pressure‐independent bandwidth of intramolecular phonons. The unusual behavior of the bandwidth was related to the instability of a ferrocene molecule caused by jumps between its D5d and D5h conformations. A decrease in the time of jumps between the conformations to the period of crystal lattice vibrations led to a loss of coherence and broadening of intermolecular phonon bands. The energy barrier between the conformations was determined to be ~17.6 meV/molecule under ambient conditions and 80 meV/molecule at 4.9 GPa. An increase in the barrier with pressure was due to the enhancement of the crystal field, which resulted in the inhibition of the jumps and the stabilization of the molecule in the D5d conformation. [ABSTRACT FROM AUTHOR]

Metastasis causes greater than 90% of cancer-associated deaths, presenting huge challenges for detection and efficient treatment of cancer due to its high heterogeneity and widespread dissemination to various organs. Therefore, it is imperative to combat cancer metastasis, which is the key to achieving complete cancer eradication. Immunotherapy as a systemic approach has shown promising potential to combat metastasis. However, current clinical immunotherapies are not effective for all patients or all types of cancer metastases owing to insufficient immune responses. In recent years, immunological nanomaterials with intrinsic immunogenicity or immunomodulatory agents with efficient loading have been shown to enhance immune responses to eliminate metastasis. In this review, we would like to summarize various types of immunological nanomaterials against metastasis. Moreover, this review will summarize a series of immunological nanomaterial-mediated immunotherapy strategies to combat metastasis, including immunogenic cell death, regulation of chemokines and cytokines, improving the immunosuppressive tumour microenvironment, activation of the STING pathway, enhancing cytotoxic natural killer cell activity, enhancing antigen presentation of dendritic cells, and enhancing chimeric antigen receptor T cell therapy. Furthermore, the synergistic anti-metastasis strategies based on the combinational use of immunotherapy and other therapeutic modalities will also be introduced. In addition, the nanomaterial-mediated imaging techniques (e.g., optical imaging, magnetic resonance imaging, computed tomography, photoacoustic imaging, surface-enhanced Raman scattering, radionuclide imaging, etc.) for detecting metastasis and monitoring anti-metastasis efficacy are also summarized. Finally, the current challenges and future prospects of immunological nanomaterial-based anti-metastasis are also elucidated with the intention to accelerate its clinical translation. [ABSTRACT FROM AUTHOR]

The droplet deposition methods in Raman spectroscopy have received considerable attention in the field of analytical sensing focusing on effective pre-concentration of the studied analyte (coffee-ring effect or small spots). This review covers different analytical applications of drop-coating deposition Raman scattering (DCDRS) and droplet deposition surface-enhanced Raman scattering (SERS) spectroscopy. Two main advantages of droplet deposition Raman techniques are considered: the drying-induced segregation of the components from the mixtures (such as body fluids) and the sensitivity of detection of various analytically important molecules. Some recent advanced applications, including clinical cancer diagnosis, are discussed and summarized. Finally, the potential and further perspectives of the droplet deposition Raman methods for analytical studies are introduced. [ABSTRACT FROM AUTHOR]

Raman spectroscopy offers a rapid and nondestructive method for qualitatively and quantitatively analyzing the molecular structure of substances. Herein, a facile and cost‐effective approach for the preparation of three‐dimensional (3D) surface‐enhanced Raman scattering (SERS) substrates is proposed, in which pyramid structures are fabricated using silicon anisotropic wet etching and silver dendrites are decorated on these silicon pyramid (PSi) substrates by immersing them in a mixture of hydrofluoric acid and silver nitrate for several minutes. The 3D SERS substrates, based on PSi coated with Ag dendrites, reveal high‐performance SERS enhancement (with an analytical enhancement factor reaching 3.54 × 1010) and can detect rhodamine 6G (R6G) in the presence of chemical enhancer (lithium chloride) at low concentrations down to 10−11 m. For glucose detection, 2‐thienylboronic acid is employed to faciliate glucose attachment to the substrate surface, achieving a detection limit as low as 10−6 m. The substrate exhibits good repeatability with a relative standard deviation of 11.223%, as well as reusability and long‐term stability for detection. The results also highlight the excellent sensitivity of the PSi‐based SERS substrate, which is expected to be instrumental in biochemical analysis and holds significant potential for developing noninvasive glucose sensor for diabetic patients using saliva samples. [ABSTRACT FROM AUTHOR]

We performed a comprehensive multi-scale phonon-mediated thermal transport study of nano-porous silicon (np-Si) films with average porosities in the range of φ = 30%–70%. This depth-resolved thermal characterization involves a combination of optical methods, including femtosecond laser-based time-domain thermo-reflectance (TDTR) with MHz modulation rates, opto-thermal micro-Raman spectroscopy, and continuum laser wave-based frequency domain thermo-reflectance (FDTR) with kHz modulation rates probing depths of studied samples over 0.5–1.2, 2–3.2, and 23–34 μm, respectively. We revealed a systematic decrease in thermal conductivity (k) with the rise of φ , i.e., with the lowering of the Si crystalline phase volumetric fraction. These data were used to validate our semi-classical phonon Monte Carlo and finite element mesh simulations of heat conduction, taking into account disordered geometry configurations with various φ and pore size, as well as laser-induced temperature distributions, respectively. At high φ , the decrease in k is additionally influenced by the disordering of the crystal structure, as evidenced by the near-surface sensitive TDTR and Rutherford backscattering spectroscopy measurements. Importantly, the k values measured by FDTR over larger depths inside np-Si were found to be anisotropic and lower than those detected by the near-surface sensitive TDTR and Raman thermal probes. This finding is supported by the cross-sectional scanning electron microscopy image indicating enhanced φ distribution over these micrometer-scale probed depths. Our study opens an avenue for nano-to-micrometer scale thermal depth profiling of porous semiconducting media with inhomogeneous porosity distributions applicable for efficient thermoelectric and thermal management. [ABSTRACT FROM AUTHOR]

High‐efficient fabrication of well‐ordered nanostructures on flexible substrates is a challenge to surface‐enhanced Raman spectroscopy (SERS) for analytical fingerprinting trace‐detection. In this work, a laser parallel nanofabrication method is reported via incident‐angle‐dependent photonic nanojet ablating Au film on the bottom surface of microsphere‐lens‐array (MLA), for combination with formed dual Au‐nanoholes (MLA/2‐AuNHs) as the flexible SERS substrates. The process parameters, i.e., pulsed laser energy, MLA diameter, Au film thickness, and laser incident angle, are optimized for high finish‐quality of dual‐AuNHs with a diameter of ≈875 nm and a tip gap of ≈90 nm. The SERS substrate demonstrates the limit of detection down to 10−11 M for 4‐nitrobenzenethiol molecules by the multiple optical regulations, including self‐aligned focusing to the hotspots and directional antenna, the strongly localized surface plasmon resonances, and optical whispering‐gallery modes for resonance energy transfer. The flexible PDMS film supporting the rigid MLA holds the SERS performance of MLA/2‐AuNHs with high flexibility. Moreover, the MLA/2‐AuNHs SERS substrate exhibits differential responses to orthogonally polarized excitation, by which the background noises can be eliminated to improve the Raman spectrum. The present work opens new opportunities to fabricate dielectric‐metal flexible SERS substrates by laser parallel nanofabrication via MLA for Raman trace detection. [ABSTRACT FROM AUTHOR]

Aflatoxin B1 (AFB1) is a mycotoxin and is the most carcinogenic of all known chemicals. In view of the AFB1 characteristics of widespread distribution, serious pollution, great harm to humans, and animals and difficult to remove, it is urgent to develop a convenient and sensitive detection method. Moreover, chromatographic test strips (CTSs) are a rapid detection technology that combines labeling technology with chromatography technology. CTSs have been widely used in the fields of environmental monitoring, medical diagnosis, and food safety analysis in recent years. Different from other immune assays, they have the advantages of short measuring time, low cost, high efficiency and no need for professionals to operate. In addition, the introduction of nanomaterials has laid a good foundation for the detection of high sensitivity, high specificity and high efficiency via CTSs. Herein, we tend to comprehensively introduce the applications of chromatographic methods in AFB1 detection and pay attention to the signal detection modes based on nanomaterials in antibody-based immunochromatographic strips (ICSs), such as colorimetric, fluorescent, chemiluminescent, and Raman scattering sensing. Some typical examples are also listed in this review. In the end, we make a summary and put forward prospects for the development of CTSs. This review is the first systematic review about the applications of antibody-/aptamer-based chromatographic methods for rapid AFB1 detection. Pay attention to the signal detection modes based on nanomaterials in antibody-ICSs, such as colorimetric, fluorescent, chemiluminescent and Raman scattering sensing. Make a summary about some typical examples and put forward prospects for the development of CTSs. [ABSTRACT FROM AUTHOR]

Recently, there has been an increased focus on investigating the possible use of ferrite nanoparticles as magnetic memory devices. In this study, we report on the structural, microstructural, Raman, density functional theory and magnetic characteristics of Mg 1-x Li x Fe 2 O 4 (x = 0, 0.15, 0.3, 0.45, 0.5 and 0.75). Samples were synthesized by solution combustion synthesis method. Samples were subjected to characterize X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman Spectra. XRD reveals that all synthesized samples show a single phase formation and unit cell volume, crystallite size varied with an increase in Lithium-ion concentration. SEM micrographs confirmed the porous nature increases with the rise of Li concentration. Particles are agglomeration and spherical type of nature was confirmed by TEM images. Further, Raman Spectra confirms the spinel cubic structure of MgFe 2 O 4 nanoparticles belongs to the Fd3m space group. Despite the fact that the full unit cell has 56 atoms (Z = 8), the smallest Bravais cell consists of only 14 atoms (Z = 2). Consequently, in order to understand this effect, the electronic structure of pure and doped models was investigated through the Band Structure and Density of States (D.O.S.) profiles. First the crystalline structure of pure and Li-doped MgFe 2 O 4 was analyzed based on the optimized lattice parameters and M − O (M = Mg, Li and Fe) bond distances. The band-gap was computed to be 2.54 eV being a direct transition between two points, in an excellent agreement with the experimental measurements. To investigate the temperature dependent magnetic properties, the M − H loops of Li doped MgFe 2 O 4 nanoparticles traced at below and above room temperature over the applied magnetic field ±60 kOe. The M − H loops recorded at above and below room temperature demonstrated that the ferromagnetic nature of the sample. Further, the magnetic properties was investigated using temperature dependent FC and ZFC magnetization measurements. Above room temperature, the ZFC and FC curves show irreversibility and split at certain temperatures, as well as a broad maximum in ZFC curves at blocking temperature (T B). Saturation magnetization (M s) values are higher at 15 K compared to 300 K, attributed to reduced thermal fluctuation. Our results suggest that synthesized materials are useful for room temperature magnetic memory device application. [ABSTRACT FROM AUTHOR]

We investigate emission characteristics, phonon–phonon, and electron–phonon interactions in a lead-free halide perovskite Cs 3 Sb 2 Br 9 through temperature-dependent photoluminescence, Raman scattering, and x-ray diffraction measurements. The exciton–optical phonon coupling leads to below bandgap broad emissions, arising from self-trapped excitons recombination. The anomalous temperature dependence of the lowest frequency Raman mode is attributed to the phonon–phonon and electron–phonon interactions. The temperature-dependent x-ray diffraction measurement reveals a minimum in the volume thermal expansion coefficient at around 120 K. We also quantify the quasiharmonic contributions to the phonon frequency shift for all Raman modes. [ABSTRACT FROM AUTHOR]

To improve the laser utilization efficiency and avoid photodamage in surface-enhanced Raman spectroscopy (SERS), it is imperative to introduce photon technology into the field of SERS detection. A major challenge is the inefficient interaction between the substrate and the incident wavelength, resulting in limited Raman enhancement at a relatively low level. Here, we sputtered plasmonic Au nanoparticles (NPs) onto photonic TiOx nanocavities, creating a novel hybrid photonic-plasmonic resonator that achieves a large degree of optical manipulation and long-term localization. By facilely controlling the size of Au NPs, the resonance wavelength of plasmonic Au NPs can be matched with the photonic nanocavity to maximize the light trapping intensity, which leads to a synergistic enhancement of SERS via the electromagnetic and chemical mechanisms, resulting in a SERS enhancement up to 1.75 × 109 under non-resonant excitation. In particular, the substrate can achieve strong absorption and localization for long wavelengths, thus enabling a large SERS enhancement with a small light intensity, which can effectively avoid the photodamage that may occur in Raman testing. The substrate can detect various biomolecules, including biomarkers in serum, thus realizing the differentiation of different cancers. This study provides a powerful and sensitive platform for SERS, facilitating bioanalysis and disease diagnosis in complex systems. [ABSTRACT FROM AUTHOR]

Within angle‐resolved polarized Raman spectroscopy (ARPRS) experiments, ensuring accurate configurations is crucial for obtaining reliable results, especially when dealing with anisotropic materials like CrOCl with anisotropic crystal structure and phonon properties. However, comprehensive understanding of phase‐dependent ARPRS and the calibration of phase angle on anisotropic phonon modes from a crystallographic perspective are still lacking. Herein, detailed investigation on phase‐dependent ARPRS and looked into the anisotropic photo‐phonon interaction in CrOCl through in situ ARPRS is conducted. The Raman tensors and crystal orientation are acquired under two typical configurations. Phase‐dependent ARPRS are thoroughly analyzed for the calibration of analyzer deviation. The anomalous anisotropic response in phase‐dependent ARPRS is closely related to the intrinsic linear dichroism (LD) effect in CrOCl, which is further confirmed by angle‐resolved polarization absorption. Moreover, the strong localized rules for various parallel energy bands of CrOCl have generated anomalous LD conversion effect near 470 nm, which expands the potential application of CrOCl in polarization‐wavelength selected devices. This findings can offer in‐depth comprehension on the anisotropic phonon physics of CrOCl and a feasible approach to utilize phase‐dependent ARPRS for probing the undiscovered abundant photo‐induced effects in low‐symmetry 2D materials. [ABSTRACT FROM AUTHOR]

In the context of the extensive application prospect of two-dimensional (2D) chalcogenides, we synthesized layered SnSe2+δ bulks with defects employing a hybrid chemical vapor transport-melt approach. Both the Eg and A1g Raman characteristic peaks in SnSe2+δ are dominated by cubic anharmonicity, coupled with nonlinear temperature dependencies below 140 K. Notably, the reduction in phonon energy observed in these vibrational modes can be ascribed to defect-mediated Raman scattering, irrespective of deficient or excess Se defects. However, the lower consistency in the Raman shifts of the in-plane Eg vibrations compared to the out-of-plane A1g modes suggests that the defects predominantly entail the absence of Se atoms and the substitutions of Sn by Se, delineating a continuum of Se-deficient and Se-enriched compositions. Furthermore, Se defects induce the contraction of the indirect bandgaps, facilitating a transition from medium to narrow bandgap semiconductors in SnSe2+δ, which underscores the tunable nature of the bandgaps through the incorporation of Se defects. These discoveries present an avenue for bandgap engineering and foster a deeper comprehension of the phonon and thermal properties of layered chalcogenides for further advanced technologies. [ABSTRACT FROM AUTHOR]

Magneto-optical measurements are fundamental research tools that allow for studying the hitherto unexplored optical transitions and the related applications of topological two-dimensional (2D) transition metal dichalcogenides (TMDs). A theoretical model is developed for the first-order magneto-resonant Raman scattering in a monolayer of TMD. A significant number of avoided crossing points involving optical phonons in the magneto-polaron (MP) spectrum, a superposition of the electron and hole states in the excitation branches, and their manifestations in optical transitions at various light scattering configurations are unique features for these 2D structures. The Raman intensity reveals three resonant splittings of double avoided-crossing levels. The three excitation branches are present in the MP spectrum provoked by the coupling of the Landau levels in the conduction and valence bands via an out-of-plane A 1 -optical phonon mode. The energy gaps at the anticrossing points in the MP scattering spectrum are revealed as a function of the electron and hole optical deformation potential constants. The resonant MP Raman scattering efficiency profile allows for quantifying the relative contribution of the conduction and valence bands in the formation of MPs. The results obtained are a guideline for controlling MP effects on the magneto-optical properties of TMD semiconductors, which open pathways to novel optoelectronic devices based on 2D TMDs. [ABSTRACT FROM AUTHOR]

The short alkyl chain of N‐octylamine was demonstrated to be able to transfer silver nanoparticles (AgNPs) from the aqueous to toluene phase with a narrow average size lower than 10 nm via ligand exchange between N‐octylamine and the sodium citrate used as a reducing and stabilizing agent during AgNPs synthesis. Surface plasmon analysis by UV‐visible spectroscopy showed that the N‐octylamine concentration significantly influences the concentration and stability of AgNPs transferred to the toluene phase and the time required for such transfer. Then, the transferred silver nanoparticles were deposited on a polydimethylsiloxane (PDMS) substrate by drop‐casting (PDMS‐T‐50‐D) or immersion (PDMS‐T‐50‐I). XPS analysis demonstrated that the AgNPs are deposited at lower than 0.02 % atomic percentages through both deposition methods. The Raman signal and the noise by fluorescence signal were shown to be significantly influenced by the AgNPs deposition method on PDMS film. The trace content of AgNPs on the flexible PDMS films on both PDMS‐T‐50‐D and PDMS‐T‐50‐I substrates can eliminate the fluorescence signal of the analyte; however, only the PDMS‐T‐50‐I substrate demonstrated a remarkable SERS‐enhanced signal. These results could significantly contribute to the design of new flexible and removable SERS substrates with ultra‐low contents of noble metal NPs. [ABSTRACT FROM AUTHOR]

A convenient self-assembly method is proposed for synthesis of 3D Au/MOF-808 (Zr) composite nanostructures with a cerium metal-organic framework loaded with gold nanoparticles. We combine adsorption properties of MOF materials with surface plasmon resonance of noble metals to construct hotspot-dense 3D Au/MOF-808 (Zr) SERS substrates, by using a two-step method of solvothermal and reduction reactions. The results show that optimal SERS substrates are obtained from a volume ratio of gold nanoparticles to MOF-808 (Zr) solution of 4:1 and a self-assembly time of 2 h. Rhodamine 6G (R6G) is used as a molecular probe to characterize and analyze SERS properties of substrates of 3D Au/MOF-808 (Zr) prepared under the optimal process conditions, where the substrates are capable to detect R6G concentrations down to 10–10 M with a relative standard deviation of 8.81%. Finally, we applied the SERS substrates of 3D Au/MOF-808 (Zr) to the detection of pesticide thiram, and establish a quantitative determination method. 3D Au/MOF-808 (Zr) provides a sensitive detection of thiram in lake water by SERS with a detection limit of 1.49 × 10−9 M. Application tests show that a SERS enhancement factor of the MOF-based SERS substrates for the detection of thiram can be significantly increased to 5.91 × 105. Thus, the above results indicate that such substrate has high sensitivity, good adsorption, homogeneity, and reproducibility, which can be extended for sensitive detection of pesticide residues in food and environment. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic underlines the need for effective strategies for controlling virus spread and ensuring sensitive detection of SARS-CoV-2. This review presents the potential of nanomaterial-enabled optical biosensors for rapid and low-cost detection of SARS-CoV-2 biomarkers, demonstrating a comprehensive analysis including colorimetric, fluorescence, surface-enhanced Raman scattering, and surface plasmon resonance detection methods. Nanomaterials including metal-based nanomaterials, metal–organic frame–based nanoparticles, nanorods, nanoporous materials, nanoshell materials, and magnetic nanoparticles employed in the production of optical biosensors are presented in detail. This review also discusses the detection principles, fabrication methods, nanomaterial synthesis, and their applications for the detection of SARS-CoV-2 in four categories: antibody-based, antigen-based, nucleic acid–based, and aptamer-based biosensors. This critical review includes reports published in the literature between the years 2021 and 2024. In addition, the review offers critical insights into optical nanobiosensors for the diagnosis of COVID-19. The integration of artificial intelligence and machine learning technologies with optical nanomaterial-enabled biosensors is proposed to improve the efficiency of optical diagnostic systems for future pandemic scenarios. [ABSTRACT FROM AUTHOR]

In this work, we synthesized the TiO2 nanowire (NW) and Gold (Au) nanoparticle (NP) aligned TiO2-NW using glancing angle deposition (GLAD) associated with e-beam evaporation technique. Further, synthesized samples annealed at 400 °C, 600 °C, and 900 °C to change crystallite nature of material. The presence of anatase phase has more percentage than rutile phase till 600 °C, while annealed at 900 °C most of phase transformed into rutile phase. XRD and Raman's spectra verified the annealing temperature phase transition. The effect of surface plasmon resonance (SPR) of Au-NP was observed in optical absorption and photoluminescence (PL) spectra. Moreover, anatase-rutile phase exhibited enhanced optical absorption. The bandgap decreases and crystallite size increases while increasing value of annealing temperature. The field emission scanning electron microscope (FESEM) images confirm the formation of TiO2-NW along with Au-NP on Si substrate. The average length and diameter of TiO2-NW were ⁓230 nm and ⁓54 nm, respectively. It was noted that the diameter of the Au-NPs varied, ranging from ⁓5 nm to ⁓10 nm. This phase transformation investigation will ultimately aid in the optimization of synthesis processes in numerous photo activity related applications. The common potential applications are photocatalysis, gas sensors, photovoltaics, memory and biomedical applications. [ABSTRACT FROM AUTHOR]