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Label-free detection of liver cancer based on silver nanoparticles coated tissue surface-enhanced Raman spectroscopy
摘要： Surface-enhanced Raman spectroscopy (SERS) was employed to obtain hepatocellular carcinoma (HCC) tissue spectra with coated silver nanoparticles. Principal component analysis (PCA) combined with linear discriminate analysis (LDA) was introduced to analyze the obtained spectra. The sensitivity and specificity of discrimination for HCC and normal group is 93.8% and 100%. While that is 79.2% and 93.8% for HCC and adjacent HCC group, this study suggests a great potential method for early HCC detection by combination of silver nanoparticles based tissue SERS and PCA-LDA analysis.
关键词： silver nanoparticles,surface-enhanced Raman spectroscopy (SERS),linear discriminate analysis,hepatocellular carcinoma,principal component analysis
更新于2025-09-09 09:28:46
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Assessing UO2 sample quality with μ-Raman spectroscopy
摘要： m-Raman spectroscopy of UO2 has demonstrated its value as a tool in nuclear forensics and for analyzing nuclear fuels, but its ability to evaluate UO2 sample quality has been relatively unexplored. To investigate this potential, a three-pronged study that uses Raman spectroscopy to analyze 1) three distinct qualities of UO2 single crystals with two different excitation lasers, 2) a high quality single crystal UO2 sample that is progressively damaged with a laser, and 3) a single crystal of UO2 grown on top of a ThO2 substrate was undertaken. The results demonstrate that the peak height ratio between the second order longitudinal optical phonon signal near 1145 cm?1 and the T2g peak located near 450 cm?1 is directly correlated with crystal quality when a 532 nm excitation source is used. Furthermore, this observed pattern relies upon the two most intense peaks that are present in the Raman spectra, making it more robust to lower signal-to-noise ratios than similar trends present in the peak height ratio between the first order longitudinal optical phonon signal near 565 cm?1 and the T2g peak. Both peak height ratios are more sensitive indicators of the crystal quality than the width ratios of the same signals or the associated wavenumber shift in the T2g peak location. The correlation between the 2LO and T2g peak heights and the overall crystal quality offers the potential to directly assess and compare the quality of different samples of single crystal UO2.
关键词： Uranium dioxide,Sample quality,m-Raman spectroscopy,UO2,Single crystal
更新于2025-09-09 09:28:46
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A Comparative Analysis of BaTiO3/(Ba,Sr)TiO3 and BaTiO3/(Ba,Sr)TiO3/SrTiO3 Artificial Superlattices via Raman Spectroscopy
摘要： BaTiO3/Ba50Sr50TiO3 and BaTiO3/Ba50Sr50TiO3/SrTiO3 superlattices are characterized via Raman spectroscopy. Special attention is paid to a comprehensive analysis of their polarized Raman spectra, especially, within a soft mode (E(1TO)) range. The shift of E(1TO) soft mode is found to be more pronounced for BaTiO3/Ba50Sr50TiO3/SrTiO3 sample than for BaTiO3/Ba50Sr50TiO3, presumably owing to stronger 2D compression of BT layers and abruptly increased temperature of transition from ferroelectric to paraelectric phase.
关键词： BaTiO3/Ba50Sr50TiO3/SrTiO3 ferroelectric superlattices,Raman spectroscopy,soft mode,strain,BaTiO3/Ba50Sr50TiO3
更新于2025-09-09 09:28:46
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Properties of ta-C coatings prepared by pulsed cathodic arc source at various distances
摘要： Tetrahedral amorphous carbon (ta-C) coatings have been prepared on silicon substrates by the pulsed cathodic arc source. For the limitation of the heat flux of the carbon plasma to the sample, the diaphragm of 27 mm diameter has been used. The deposition process has been carried out at three different distances between the arc source and the substrate: 150, 215 and 265 mm. The properties of ta-C coatings have been studied by Raman spectroscopy and dynamic nanoindentation techniques. The analysis of Raman spectra parameters has revealed that the concentration of ordered aromatic rings in Csp2 cluster decreases with distance between the arc source and the substrate while the concentration of chain groups increases. Nanoindentation has shown the decrease in nanohardness and Young's modulus with the distance. Nanohardness value falls from 21 GPa to 16 GPa and Young's modulus value goes down from 197 GPa to 177 GPa. So, it’s possible to control the formation of ta-C coatings structure by changing distance between the pulsed cathodic arc source and the substrate.
关键词： ta-C coatings,nanohardness,Young's modulus,pulsed cathodic arc source,nanoindentation,Raman spectroscopy
更新于2025-09-09 09:28:46
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Raman study of the vibration eigenmodes of CePt <sub/>5</sub> films on Pt(111)
摘要： The surface intermetallic rare-earth compound CePt5 in the range of few unit cells has a high relevance in the field of Kondo- and heavy fermion physics. Besides, it shows an intriguing crystal-lattice development, which is expected to be reflected in its vibration modes. We present a temperature-dependent vibrational frequency- and symmetry analysis by polarized Raman spectroscopy on CePt5 films and for comparison isostructural LaPt5 films. Three CePt5 eigenmodes with characteristic symmetry properties occur with frequencies around 100, 120, and 130 cm?1. By group-theoretical analysis and from the evolution of their intensities they are attributed to the E g2 mode of the bulk-like CePt5 film and E2- and A1 modes of a symmetry-reduced CePt5 top layer, respectively. Thus, they confirm the model, derived by low-energy electron diffraction, of this material system regarding structure and strain development. The LaPt5 vibration peaks are qualitatively similar. Slight frequency shifts of the latter are mainly attributed to a modified strain development. Finally, an anomalous low-temperature frequency shift occurs for the A1 mode of the CePt5 top layer, which might indicate an interaction with the 4f electron system.
关键词： surface Raman spectroscopy,LaPt5,CePt5,surface vibrations
更新于2025-09-09 09:28:46
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A novel urine analysis technique combining affinity chromatography with Au nanoparticle based SERS spectroscopy for potential applications in noninvasive cancer screening
摘要： Modified nucleoside in urine samples is one of the most common biomarkers for cancer screening. Therefore, we developed a novel detection method for modified nucleoside detection in human urine. In this work, the modified nucleoside from real cancer patient's urine samples was firstly separated and purified using the affinity chromatography (AC) technology relying on its specific adsorption capacity. Then, a surface enhanced Raman spectroscopy (SERS) technology with the capable of single molecular detection was employed for sensitively characterizing the biomolecular features of modified nucleoside. A total of 141 high quality SERS spectra of urinary modified nucleoside can be obtained from 50 gastric cancer patients, 43 breast cancer patients as well as 48 healthy volunteers. Using principal component analysis combined with linear discriminant analysis (PCA-LDA), the diagnostic sensitivities for identifying gastric cancer vs. normal, breast cancer vs. normal, gastric cancer vs. breast cancer were 84.0%, 76.7% and 82.0%, respectively. And the corresponding diagnostic specificities for each combination were 95.8%, 87.5% and 90.7%, respectively. These results show that this novel method based on urinary modified nucleoside detection combining AC and SERS technologies holds promising potential for developing a specific, non-invasive and label-free tool for cancer screening.
关键词： surface enhanced Raman spectroscopy (SERS),modified nucleoside,cancer screening,affinity chromatography
更新于2025-09-09 09:28:46
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Temperature and pressure induced Raman studies of C 60 oxide
摘要： We present temperature, laser power, and pressure dependent Raman spectral analysis of C60 oxide (C60O) thin films prepared by the photolysis method. The first order temperature, laser power, and pressure coefficients of the Raman frequencies are evaluated and are utilized for evaluating the thermal conductivity of C60O. Its thermal conductivity is found to be 0.7 W m-1 K-1 which is marginally higher than that of bulk C60. Raman frequencies corresponding to C–O and C–C bonds blue-shift with a decrease in temperature which is attributed to the thermal contraction of C60O molecules. The density functional measurements have been performed to optimize C60O structure. The contraction in the C–O bond length has been corroborated with the experimental Raman shifts at different temperatures and is used to evaluate the linear expansion coefficient of C60O. Pressure induced compression and polymerization of C60O clusters are also illustrated. This study highlights the interplay between thermal and mechanical transformations in the C60O cluster which may regulate its thermoelectric properties by tuning the intermolecular interactions.
关键词： pressure dependence,thermoelectric properties,Raman spectroscopy,thermal conductivity,C60 oxide,laser power dependence,temperature dependence
更新于2025-09-09 09:28:46
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Transformation of the Anion Sublattice in the Cation-Exchange Synthesis of Au <sub/>2</sub> S from Cu <sub/>2-x</sub> S Nanocrystals
摘要： Cation exchange is a versatile post-synthetic technique that has been exploited in the synthesis of metastable nanocrystals through preservation of the anion sublattice. Here we report on the mechanistic details of the synthesis of metastable Au2S via cation exchange with Cu2-xS nanocrystals. This conversion requires a transformation of the anion sublattice, from hcp in Cu2-xS to bcc Au2S accompanied by an expansion of the unit cell. The ligand environment plays a key role in the driving force of the reaction as the presence of oleylamine allows the conversion to proceed at room temperature while the addition of trioctylphosphine hinders the reaction. By employing transmission electron microscopy (TEM) on faceted nanocrystals and partial cation exchange of nanocrystals, it was demonstrated that the reaction proceeds in a highly directional manner through the pyramidal facets. Since cation exchange produces high quality nanocrystals as seen through XRD and TEM, UV-Vis and Raman spectroscopy were used to characterize the optoelectronic properties of the metastable Au2S nanocrsytals. A Tauc plot analysis revealed a band gap of 2.6 eV, while two intrinsic Raman modes were identified at 265 cm-1 and 329 cm-1. Density functional theory (DFT) calculations of structures, energy bands, optical spectra, and phonon spectra were performed and combined with the experimental data to provide additional insights into the characterization of Au2S nanocrystals.
关键词： XRD,Raman spectroscopy,UV-Vis,trioctylphosphine,nanocrystals,TEM,Cation exchange,DFT,Cu2-xS,anion sublattice transformation,Au2S,oleylamine
更新于2025-09-09 09:28:46
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Light Emission by Nanoporous GaN Produced by a Top-Down, Nonlithographical Nanopatterning
摘要： Temperature-dependent photoluminescence (PL) spectroscopy is carried out to probe radiative recombination and related light emission processes in two-dimensional periodic close-packed nanopore arrays in gallium nitride (np-GaN). The arrays were produced by nonlithographic nanopatterning of wurtzite GaN followed by a dry etching. The results of Raman spectroscopy point to a small relaxation of the compressive stress of ~0.24 GPa in nanoporous vs. bulk GaN. At ~300 K, the PL emission is induced by excitons and not free-carrier interband radiative recombinations. An evolution of the emission spectra with T is con?rmed to be mainly a result of a decay of nonexcitonic PL emission and less of spectral shifts of the underlying PL bands. A switching of excitonic PL regime observed experimentally was analyzed within the exciton recombination-generation framework. The study provides new insights into the behaviors and physical mechanisms regulating light emission processes in np-GaN, critical to the development of nano-opto-electronic devices based on mesoscopic GaN.
关键词： photoluminescence,nonlithographic nanopatterning,Raman spectroscopy,nanoporous GaN,excitonic emission
更新于2025-09-09 09:28:46
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PDMS-Au/Ag Nanocomposite Films as Highly Sensitive SERS Substrates
摘要： Polydimethylsiloxane (PDMS)–gold/silver nanoparticle composite films were synthetized in situ by using a simple method, which is based on the reduction of chloroauric acid (HAuCl4) or silver nitrate solution (AgNO3) by the PDMS membrane. A method to monitor the development of the plasmonic absorbance peak in situ (during the synthesis of the nanoparticles) is introduced in order to provide a convenient way to investigate the effect of the technological parameters on the position of the resulting peak. The resulting composite films were tested as SERS substrates at two excitation wavelengths (488 nm, 785 nm) and the preliminary results indicate that they are promising candidates for this application, with high sensitivities accompanied by cheap fabrication costs.
关键词： gold,SERS,Raman-spectroscopy,PDMS,silver,nanocomposites
更新于2025-09-09 09:28:46