Relative Peak Positions Research Articles

Simultaneous Second Harmonic Generation and Multiphoton Excited Photoluminescence in Samarium-Doped BaTiO3 Nanoparticles Functionalized with Poly(ethylene glycol).

In this work, samarium-doped BaTiO3 (BT:Sm) nanoparticles (NPs) were prepared and coated with poly(ethylene glycol) (PEG) to investigate their optical characteristics and compatibility with biological systems. The structure, particle morphology, optical properties, and biological compatibility of the NPs were assessed. The results demonstrated the formation of BT:Sm and [(BT:Sm)-PEG]. The relative intensities and positions of peaks in the X-ray diffraction (XRD) are consistent with an average crystallite size of ∼75 nm. The Raman spectra showed that Sm doping produced the typical tetragonal peaks at around 306 and 715 cm-1, and Fourier transform infrared (FTIR) spectroscopy showed that the PEGylation process was effective. Also, our investigation demonstrates the potential of these NPs as very temperature-sensitive nanosensors with a resolution exceeding 0.5 °C, which is achievable through optical excitation. We also analyze their emission properties. Finally, we present a study related with the mitochondrial activity of naked and PEG-coated NPs. The results indicate that neither naked nor PEG-coated NPs exhibit changes in mitochondrial metabolism, as indicated by quantitative cell viability and morphological visualization. The PEG-coated NPs prevented the formation of aggregates in cell culture compared to naked NPs, demonstrating the significance of PEG as a stabilizing agent.

Effects of the Intramolecular Group and Solvent on Vibrational Coupling Modes and Strengths of Fermi Resonances in Aryl Azides: A DFT Study of 4-Azidotoluene and 4-Azido-N-phenylmaleimide.

The high transition dipole strength of the azide asymmetric stretch makes aryl azides good candidates as vibrational probes (VPs). However, aryl azides have complex absorption profiles due to Fermi resonances (FRs). Understanding the origin and the vibrational modes involved in FRs of aryl azides is critically important toward developing them as VPs for studies of protein structures and structural changes in response to their surroundings. As such, we studied vibrational couplings in 4-azidotoluene and 4-azido-N-phenylmaleimide in two solvents, N,N-dimethylacetamide and tetrahydrofuran, to explore the origin and the effects of intramolecular group and solvent on the FRs of aryl azides using density functional theory (DFT) calculations with the B3LYP functional and seven basis sets, 6-31G(d,p), 6-31+G(d,p), 6-31++G(d,p), 6-311G(d,p), 6-311+G(d,p), 6-311++G(d,p), and 6-311++G(df,pd). Two combination bands consisting of the azide symmetric stretch and another mode form strong FRs with the azide asymmetric stretch for both molecules. The FR profile was altered by replacing the methyl group with maleimide. Solvents change the relative peak position and intensity more significantly for 4-azido-N-phenylmaleimide, which makes it a more sensitive VP. Furthermore, the DFT results indicate that a comparison among the results from different basis sets can be used as a means to predict more reliable vibrational spectra.

Elongation induced demonstration of the fraction dependent filler network structures in silicone rubber: An in situ SAXS study

Aiming to unveil the filler network structures in silicone rubber with various filler volume fraction (ΦSi), in situ tensile-small-angle x-ray scattering (SAXS) was conducted on composites with ΦSi of 0%, 11.9%, 18.4%, and 26.5% (S0, S30, S50, and S80). For the static state of S30, S50, and S80, the aggregates sizes decrease from 65 nm, 53 nm–42 nm, while the homogeneity of aggregates and filler network is improved. With the help of in situ SAXS, intrinsic differences of filler networks on vertical (V) and horizontal (H) of the elongation direction related to ΦSi are further unveiled. During elongation, the relative stable peak position in medium-q range of Kratky plots indicate that the aggregates as a stable unit (form factor) of the filler network. In V direction, the almost unchanged intensity of S30 indicates the insignificant changes statistically due to high heterogeneity of filler network. The decreased low-q intensity of S80 indicates the compression of relatively homogeneous filler network. While in H direction, additional peaks appear for all the samples, which are low-q shift with increasing the strain. However, for S30, the peaks mainly come from the separation of the initially adjacent aggregates. For S80, the clear increased low-q intensity suggests the initial existed correlation length is expanded.

Structural characterization, stability, and cytocompatibility study of chitosan BaTiO3@ZnO:Er heterostructures

New imaging agents are required in cancer diagnosis to enhance the diagnostic accuracy, classification, and therapeutic management of tumors. Nanomaterials have emerged as a promising alternative to developing new nanostructures with imaging applications. In this study, a heterostructure based on barium titanate (BT), zinc oxide (ZnO), and erbium (Er) was prepared and coated with Chitosan (CS) to investigate their stability and compatibility with biological systems. The structure, particle morphology, luminescence properties, stability, and cytotoxicity of different nanoparticles (NPs) were assessed. The results demonstrated the formation of a [BT@ZnO:Er]-CS heterostructure, which is consistent with the relative intensities and positions of peaks in the X-ray diffraction (XRD) with an average crystallite size of ~76 nm. The electrokinetic measurement results indicate that the coated NPs are the most stable and have an average size close to 200 nm when the pH is between 3 and 5. Finally, we presented a cytotoxicity study of naked and CS-coated NPs. The results indicate that naked NPs exhibit varying cellular toxicity, as indicated by decreased cell viability, morphological changes, and an increase in an apoptotic marker. The CS-coated NPs prevented the cytotoxic effect of the naked NPs, demonstrating the significance of CS as a stabilizing agent.

Transition-potential coupled cluster II: optimisation of the core orbital occupation number

The issue of orbital relaxation in computational core-hole spectroscopy, specifically x-ray absorption, has been a major problem for methods such as equation-of-motion coupled cluster with singles and doubles (EOM-CCSD). The transition-potential coupled cluster (TP-CC) method is utilised to address this problem by including an explicit treatment of orbital relaxation via the use of reference orbitals with a fractional core occupation number. The value of the fractional occupation parameter λ was optimised for both TP-CCSD and XTP-CCSD methods in an element-specific manner due to the differences in atomic charge and energy scale. Additionally, TP-CCSD calculations using the optimised parameters were performed for the K-edge absorption spectra of gas-phase adenine and thymine. TP-CCSD reproduces the valence region well and requires smaller overall energy shifts in comparison to EOM-CCSD, while also improving on the relative position and intensities of several absorption peaks.

Accurate Core-Excited States via Inclusion of Core Triple Excitations in Similarity-Transformed Equation-of-Motion Theory.

The phenomenon of orbital relaxation upon excitation of core electrons is a major problem in the linear-response treatment of core-hole spectroscopies. Rather than addressing relaxation through direct dynamical correlation of the excited state via equation-of-motion coupled cluster theory (EOMEE-CC), we extend the alternative similarity-transformed equation-of-motion coupled cluster theory (STEOMEE-CC) by including the core-valence separation (CVS) and correlation of triple excitations only within the calculation of core ionization energies. This new method, CVS-STEOMEE-CCSD+cT, significantly improves on CVS-EOMEE-CCSD and unmodified CVS-STEOMEE-CCSD when compared to full CVS-EOM-CCSDT for K-edge core-excitation energies of a set of small molecules. The improvement in both absolute and relative (shifted) peak positions is nearly as good as that for transition-potential coupled cluster (TP-CC), which includes an explicit treatment of orbital relaxation, and CVS-EOMEE-CCSD*, which includes a perturbative treatment of triple excitations.

Determining the Oxygen Stoichiometry of Cobaltite Thin Films

Transition metal oxides (TMOs) are promising materials to realize low-power neuromorphic devices. Their physical properties critically depend on their oxygen vacancy concentration, whose experimental determination remains a challenging task. Here, we focus on cobaltites, in particular La1–xSrxCoO3−δ (LSCO), and present a strategy to identify fingerprints of oxygen vacancies in X-ray absorption (XA) spectra. Using a combination of experiments and theory, we show that the variation of the oxygen vacancy concentration in the perovskite phase of LSCO is correlated with the change in the relative peak positions of the O K-edge XA spectra. We also identify an additional geometrical fingerprint that captures both the changes in the Co–O bond length and Co–O–Co bond angle in the material due to the presence of oxygen vacancies. Finally, we predict the oxygen vacancy concentration of experimental samples and show how the resistivity of the oxide material may be tuned as a function of the defect concentration, in the absence of any structural transformation. Our study shows that, in order to predict the complex transport properties of TMOs, it is crucial to gain a detailed understanding of their oxygen defect density.

Covalency in actinide(iv) hexachlorides in relation to the chlorine K-edge X-ray absorption structure.

Chlorine K-edge X-ray absorption near edge structure (XANES) in actinideIV hexachlorides, [AnCl6]2− (An = Th–Pu), is calculated with relativistic multiconfiguration wavefunction theory (WFT). Of particular focus is a 3-peak feature emerging from U toward Pu, and its assignment in terms of donation bonding to the An 5f vs. 6d shells. With or without spin–orbit coupling, the calculated and previously measured XANES spectra are in excellent agreement with respect to relative peak positions, relative peak intensities, and peak assignments. Metal–ligand bonding analyses from WFT and Kohn–Sham theory (KST) predict comparable An 5f and 6d covalency from U to Np and Pu. Although some frontier molecular orbitals in the KST calculations display increasing An 5f–Cl 3p mixing from Th to Pu, because of energetic stabilization of 5f relative to the Cl 3p combinations of the matching symmetry, increasing hybridization is neither seen in the WFT natural orbitals, nor is it reflected in the calculated bond orders. The appearance of the pre-edge peaks from U to Pu and their relative intensities are rationalized simply by the energetic separation of transitions to 6d t2gversus transitions to weakly-bonded and strongly stabilized a2u, t2u and t1u orbitals with 5f character. The study highlights potential pitfalls when interpreting XANES spectra based on ground state Kohn–Sham molecular orbitals.

Characterizing spatial variations of PAH emission in the reflection nebula NGC 1333

ABSTRACT Infrared emission features at 3.3, 6.2, 7.7, 8.6, and 11.2 µm, attributed to polycyclic aromatic hydrocarbons (PAHs), show variations in relative intensity, shape, and peak position. These variations depend on the physical conditions of the photodissociation region (PDR) in which strong PAH emission arises but their relationship has yet to be fully quantified. We aim to better calibrate the response of PAH species to their environment using observations with matching apertures and spatial resolution. We present observations from the Field-Imaging Far-Infrared Line Spectrometer onboard the Stratospheric Observatory for Infrared Astronomy of the gas cooling lines [O i] 63, 146 µm and [C ii] 158 µm in the reflection nebula NGC 1333 and use archival dust continuum observations from the Photodetector Array Camera and Spectrometer (PACS) onboard Herschel. We employ PDR modelling to derive the physical conditions and compare these with the characteristics of the PAH emission as observed with the Infrared Spectrometer onboard Spitzer. We find distinct spatial characteristics for the various PAH spectral components. We conclude that the ionic bands (6.2, 7.7, 8.6, and 11.0) and the 7–9 µm emission are due to multiple PAH subpopulations and that the plateaus are distinct from the features perched on top. The 6–9 µm PAH emission exhibits a significant change in behaviour between the irradiated PDR and diffuse outskirts, confirming these bands arise from multiple PAH subpopulations with different underlying molecular properties. We find multiple promising relationships between PAH ratios and the far-ultraviolet radiation field strength but no clear correlations with the PAH ionization parameter.

Component identification for Raman spectra with deep learning network

Raman spectroscopy is widely used in the research of the molecular structure of substances because of the advantages of no invasion, no damage and no interference from water. Meanwhile, component identification for mixtures is still challenging in Raman spectra. In this paper, a graphics-based sample-generating method and a model based on deep-learning for component identification was proposed. Convolution neural network (CNN) model is an important part of deep learning network and CNN models was utilized to assess the possibility of the presence of components in samples. As is shown in the comparative studies, the model was sensitive to the relative position of the characteristic peaks and could learn spectra features in mixtures. The deep-learning based component identification method showed more robustness than conventional linear fitting methods. Therefore, the method provided a valid approach to component identification for mixtures and has the potential in spectra component analysis.

Quad-Fabry-Perot etalon based Rayleigh Doppler lidar for 0.2-60km altitude wind, temperature and aerosol accurate measurement

Rayleigh Doppler lidar based on a quad Fabry-Perot etalon (FPE) is proposed that is capable of accurately detecting wind speed, as well as temperature and aerosol from 0.2 to 60km altitude. The structure of lidar is designed and its measurement principle is analyzed. One of the four FPEs, i.e. FPE-L is used for locking and measuring the outgoing laser frequency, and the other three, i.e. FPE-1, -2 and -3 form a three-stage FPE. The first-stage FPE (FPE-1) can effectively filter out Mie backscattering signal, thereby suppressing its effects on wind measurement and measuring the aerosol backscatter ratio as well. The transmission spectra of the second- and third-stage FPEs (FPE-2,-3) form double edge for simultaneous wind and temperature measurements by using Rayleigh backscattering signal. The parameters of the quad FPE are optimized. The FWHM and relative peak position of FPE-1,-2,-3,-L are 0.6, 1.2, 1.2, 0.6GHz and 0, -1, 1, 0.3GHz, respectively. The performance of the proposed lidar is simulated and results show that for 0.3WSr−1m-2nm−1@355nm sky brightness, by using a 350mJ pulse energy, 50Hz repetition frequency laser and a 0.8m aperture telescope, with temporal resolution of 2min@0.2∼20km, 20min@20∼60km and vertical resolution of 45m@0.2∼10km, 90m@10∼ 20km, 180m@20∼40km, 1km@40∼60km, the measurement errors of temperature, aerosol backscattering ratio and vertical wind speed are below 5.3K, 3.0×10-3, 1.1m/s in nighttime and below 14.6K, 8.1×10-3, 2.5m/s in daytime from 0.2 to 60km altitude; the measurement error of two other orthogonal LOS wind speed with fixed zenith angle of 25.8° is below 1.3m/s in nighttime and 3.5m/s in daytime within the LOS wind speed dynamic range of ±50m/s from 0.2 to 60km altitude.

Revealing the evolving mixture of molecular aggregates during organic film formation using simulations of in situ absorbance.

In this work, we introduce a method for modeling the evolving absorbance spectrum of an organic molecule, pseudoisocyanine (PIC), measured during the process of molecular aggregation. Despite being historically considered a J-aggregate, we find that the absorbance spectrum of PIC cannot be adequately modeled using solely J-aggregates either during molecular aggregation or in the final dry film. The collection of absorbance spectra during solution-casting is particularly difficult since a distribution of aggregates with various sizes and structures can coexist. Here, spectra measured during film formation are fit to a weighted sum of simulated spectra of two aggregate species, revealing the combinations of Coulombic coupling values, Huang-Rhys parameters, and aggregate sizes that provide good fits to measured spectra. The peak intensity ratios and relative peak positions are highly sensitive to the aggregate structure, and fitting only these features enables the rapid comparison of aggregate combinations. We find that the spectra of PIC aggregates cannot be modeled using the Huang-Rhys factor of the PIC monomer, as is typically assumed, leading us to consider models that utilize independent Huang-Rhys factors for each aggregate species. This method of fitting only the key spectral features allows an experimental spectrum to be modeled within 1 h-2 h when using a single Huang-Rhys factor, making the simulation of a series of in situ measurements during aggregation computationally feasible.

Chitosan coating of BaTiO3@ZnO:Yb heterostructures: synthesis and properties

In this study, BT@ZnO:Yb heterostructures prepared using the combined sol-gel-hydrothermal methods were coated with chitosan (Qo) to obtain a hybrid heterostructure [BT@ZnO:Yb]-Qo. The structure, particle morphology, luminescence properties, and cytotoxicity of the hybrid heterostructure are discussed. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FT-IR) as well as Raman and photoluminescence spectra, were used for characterisation and monitoring of the heterostructure formation process. The results reveal the formation of the BT@ZnO:Yb heterostructure, and are consistent with the relative intensities and positions of peaks in the XRD spectra of BT and ZnO:Yb, with the average particle size of ~75 nm. Effective Qo coating was achieved and a narrow, well-defined, and high-intensity luminescence signal was detected at ~610 nm for all the analysed samples. In vitro studies suggested that treatment with 1 µg/ml BT@ZnO:Yb 3 mol% induced very low cytotoxicity on HeLa cells.

Green's function coupled cluster simulation of the near-valence ionizations of DNA-fragments.

Accurate description of the ionization process in DNA is crucial to the understanding of the DNA damage under exposure to ionizing radiation and the exploration of the potential application of DNA strands in nanoelectronics. In this work, by employing our recently developed Green's function coupled-cluster library on supercomputing facilities, we have studied the spectral functions of several guanine-cytosine (G-C) base pair structures ([G-C]n, n = 1-3) for the first time in a relatively broad near-valence regime ([-25.0, -5.0] eV) in the coupled-cluster with singles and doubles level. Our focus is to give a preliminary many-body coupled-cluster understanding and guideline of the vertical ionization energy (VIE), spectral profile, and ionization feature changes of these systems as the system size expands in this near-valence regime. The results show that, as the system size expands, even though the lowest VIEs keep decreasing, the changes of spectral function profile and the relative peak positions get unexpectedly smaller. Further analysis of the ionized states associated with the most intensive peak in the spectral functions reveals non-negligible |2h, 1p⟩'s in the ionized wave functions of the considered G-C base pair systems. The leading |2h, 1p⟩'s associated with the main ionizations from the cytosine part of the G-C base pairs feature a transition from the intra-base-pair cytosine π → π* excitation to the inter-base-pair electron excitation as the size of G-C base pairs expands, which also indicates the minimum quantum region in the many-body calculations of DNA systems.

HERFD-XANES probes of electronic structures of ironII/III carbene complexes.

Iron centered N-heterocyclic carbene (Fe-NHC) complexes have shown long-lived excited states with charge transfer character useful for light harvesting applications. Understanding the nature of the metal-ligand bond is of fundamental importance to rationally tailor the properties of transition metal complexes. The high-energy-resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) has been used to probe the valence orbitals of three carbene complexes, [FeII(bpy)(btz)2](PF6)2 (bpy = 2,2'-bipyridine, btz = 3,3'-dimethyl-1,1'-bis(p-tolyl)-4,4'-bis(1,2,3-triazol-5-ylidene)), [FeIII(btz)3](PF6)3, and [FeIII(phtmeimb)2]PF6 (phtmeimb = [phenyl(tris(3-methylimidazol-2-ylidene))borate]-). The multiconfigurational restrict active space (RAS) approach has been used to simulate the metal K pre-edge X-ray absorption spectroscopy of these carbene complexes, and have reproduced the metal K pre-edge spectral features in terms of relative intensity and peak positions. The evident intensity difference between the FeII and the other two FeIII complexes has been elucidated with different intensity mechanisms in the transition. The smaller splitting between the t2g and eg character peak for [FeIII(btz)3](PF6)3 has been observed in the experimental measurements and been reproduced in the RAS calculations. The results show how the combination of experimental HERFD-XANES measurements and ab initio RAS simulations can give quantitative evaluation of the orbital interactions between metal and ligands for such large and strongly interacting systems and thus allow to understand and predict properties of novel complexes.

First-principles calculations of the atomic structure and electronic states of LixFeF3

We calculate the atomic and electronic structures of trirutile-type ${\mathrm{Li}}_{x}{\mathrm{FeF}}_{3}\phantom{\rule{4pt}{0ex}}(x=0,0.25,0.5,0.75,\phantom{\rule{4pt}{0ex}}\text{and}\phantom{\rule{4pt}{0ex}}1)$ by first-principles calculations and evaluate the relative stability among the optimized structures by energy analysis. ${\mathrm{Li}}_{0.5}{\mathrm{FeF}}_{3}$ is more stable than the three-phase coexistence of ${\mathrm{FeF}}_{3},{\mathrm{FeF}}_{2}$, and LiF, whereas the other compositions are unstable. The analyses of the local electron density, local atomic volume, and local atomic configurations show that the formal valence of Fe atoms decreases from trivalent (3+) to divalent (2+) after Li insertion. In addition, we calculate Fe $K$-edge x-ray absorption near-edge structure (XANES) spectra in ${\mathrm{Li}}_{x}{\mathrm{FeF}}_{3}$ and compare them with observed spectra. The calculated XANES spectra agree well with the corresponding observed spectra in areas such as the spectral shape and relative position of the main peaks associated with ${\mathrm{Fe}}^{3+}$ and ${\mathrm{Fe}}^{2+}$. In particular, partial XANES spectra of ${\mathrm{Fe}}^{3+}$ in ${\mathrm{Li}}_{x}{\mathrm{FeF}}_{3}$, for $x=0.25,0.5$, and 0.75, have a specific peak between the main peaks, associated with ${\mathrm{Fe}}^{3+}$ and ${\mathrm{Fe}}^{2+}$. The detailed study reveals that the energy level and intensity ratio of the ${\mathrm{Fe}}^{3+}$ main peaks depend on the adjacent cation site of Fe.

Significant Reduction of Defect States and Surface Tailoring in ZnO Nanoparticles via Nano-Bio Interaction With Glucose for Bio-Applications.

In this study, we have investigated the structural and optical properties of nanoconjugates (NJs) consisting of phase pure zinc oxide (ZnO) nanoparticles (NPs) with glucose biomolecules. All NJs were fabricated using a standard biochemical synthesis process. Structural, optical, vibrational, and biochemical interface properties of nano-bio composites are probed by different complementary characterization techniques. The XRD patterns of the NPs and NJs illustrate a highly phase pure ZnO structure. A visible green emission in the photoluminescence spectrum, mainly associated with the oxygen vacancies on the surface of ZnO nanostructure, is significantly reduced by the incorporation of glucose biomolecules. The strong binding interaction of glucose biomolecule on the surface of ZnO NPs results in the reduction in green-yellow-orange emission intensities. The interaction of glucose molecules modifies oxygen vacancies by capturing free electrons from the ZnO surface region. Significant changes in the peak intensity and relative peak position of some of the glucose and ZnO NPs in Raman spectra refer to the direct binding between these two nano- and bio-components. In the X-ray photoelectron spectroscopy, the binding energy of O 1s core level in NJs increases from 531 eV (O 1s core level position for ZnO) and the increment is more with higher initial glucose concentration in the solution during synthesis. This study serves as a promising platform for the development of new kinds of NJs and investigation of their interfacial properties which can take the frontier forward for integration and multifunctionality.

Nonlinear acoustic response of two bubble oscillators

It is of great importance to investigate the dynamics of the multiple bubble system for revealing the mechanism of cavitation. Because of the secondary radiation of the oscillating bubbles, the coupled vibration of neighboring bubbles arises. Previous studies have reported that time delays appear to be more important when the coupled bubbles are close to each other. In this paper, we investigate the acoustical response of two bubble oscillators theoretically and numerically. Firstly, we modify the dynamic model equation by use of Taylor series being accurate up to terms of second order in radial displacement of bubbles. Based on the perturbation theory, the eigenmodes of the coupled-bubble system are analyzed, and two different resonant frequencies are obtained. Secondly, the effects of time delays on the coupled oscillation are analyzed numerically by use of phase diagram. When bubbles are driven by low-intensity ultrasound, we can neglect the effect of the time delay for the coupled-bubble system. Thirdly, the theoretical and numerical curve of amplitude versus frequency are compared with each other. There are two peaks on each curve on which present are two resonant regions. The relative position of the resonant peaks of the two bubbles in each region is similar for the two analytical methods. Finally, the effect of equivalent radius of bubble, equivalent radius ratio, bubble center distance, and driving pressure amplitude on the radial motion are numerically explored. With the increase of the intensity of the acoustic wave, the resonant peaks shift toward the low-frequency region. The coupled oscillation of the two bubbles of different radii could be intensified when these conditions are satisfied, such as resonant driving, equal radius, and the range of center distance smaller than 10<i>R</i><sub>10</sub>. We can observe a transition phenomenon and out-of-phase fluctuation of the bubble oscillation in the strong coupling region. Therefore, bubbles play an important role of energy translator in the ultrasound applications.

Correlation between effective snow grain size and hyper-spectral absorption peak characteristics – A case study over the North West Himalaya

ABSTRACTRadiative transfer theory based retrievals of effective snow grain size (SGS), albedo were widely explored using hyper-spectral sensors. However, investigation of linkage between diagnostic absorption peak characteristics (PCs) and snow surface parameters remained scarce, though these are significant to determine composition and state of material. In present study, field data acquired during three winter seasons was analyzed to study variability of effective SGS with PCs (i.e. relative depth, peak position and asymmetry). Effective SGS was found positively correlated with relative depth, with correlation of 90% and 86% for absorption peaks around 1.24 µm and 1.03 µm respectively. Asymmetry was found in good correlation with SGS (74%) at 1.24 µm than at 1.03 µm (21%). Further, PCs were derived using Hyperion data in ENVI software on pixel basis. Significance of PCs is described and compared with effective SGS, which was retrieved using widely accepted Asymptotic Radiative Transfer model. This work provide an alternate approach to infer state of snow metamorphism using peak characteristics, in scarcity of reference spectral database of snow classes.

Probing Interaction between Individual Submonolayer Nanoislands and Bulk MoS2 Using Ambient TERS

Tip-enhanced Raman spectroscopy (TERS) has shown that detecting single molecules with a high spatial resolution is possible in ultrahigh vacuum (UHV) at low temperature with plasmonic metallic substrates. It is still challenging to probe interactions of molecules with semiconductors, which is important in biosensing, photovoltaics, and many other applications. Here we demonstrate that in ambient conditions it is possible to obtain Raman signals from submonolayer molecular islands on bulk MoS2 using TERS. Analysis of relative Raman signal intensity ratio and Raman spectral peak position from spatial TERS mapping showed differences in the adsorbate–adsorbate and adsorbate–substrate interactions on Au and MoS2 substrates. The Raman transition which involves the vibration of the metal center of the CuPc molecule experienced a change in the relative Raman signal intensity ratio due to the differences in the molecule–substrate charge transfer interaction. In comparison to the other vibrational modes, the vibrat...