- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Quantum Confinement Induced Excitonic Mechanism in Zinc-Oxide-Nanowalled Microrod Arrays for UV–Vis Surface-Enhanced Raman Scattering
摘要： We studied surface-enhanced Raman spectroscopy (SERS) in 4-mercaptopyridine (4-Mpy) deposited on zinc oxide (ZnO) nanostructures, by using resonance Raman scattering covering a range of incident photon energies from 1.7 to 5.7 eV. We investigated all primary routes of the energy-specific resonances that are associated with the electronic transitions between the ZnO valence band (VB) to the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) to the ZnO conduction band (CB), respectively. Two resonances at 5.55 and 5.15 eV in the ultraviolet (UV) spectral range can be associated with transitions into the CB and most importantly into an excitonic-related state below the ZnO CB, respectively. The energy difference between the UV resonances is 0.4 eV corresponding to the excitonic binding energy as a result of excitonic quantum confinement in the 10?20 nm thick ZnO nanowalls. The observed excitonic SERS resonance enhancement of the ring-breathing mode of 4-Mpy is about 15 times stronger than for the VB resonance observed at 2.43 eV and free of luminescence background. Hence, we outline new pathways of improving the detectability of molecules by chemical SERS due to tuning of the quantum confinement in the excitonic resonance enhancement.
关键词： quantum confinement,surface-enhanced Raman spectroscopy,excitonic mechanism,UV-Vis,ZnO,SERS,zinc oxide
更新于2025-09-16 10:30:52
-
Surface-Enhanced Absorption Spectroscopy for Optical Fiber Sensing
摘要： Visible and near-infrared spectroscopy are widely used for sensing applications but suffer from poor signal-to-noise ratios for the detection of compounds with low concentrations. Enhancement by surface plasmon resonance is a popular technique that can be utilized to increase the signal of absorption spectroscopy due to the increased near-field created close to the plasmons. Despite interest in surface-enhanced infrared absorption spectroscopy (SEIRAS), the method is usually applied in lab setups rather than real-life sensing situations. This study aimed to achieve enhanced absorption from plasmons on a fiber-optic probe and thus move closer to applications of SEIRAS. A tapered coreless fiber coated with a 100 nm Au film supported signal enhancement at visible wavelengths. An increase in absorption was shown for two dyes spanning concentrations from 5 × 10?8 mol/L to 8 × 10?4 mol/L: Rhodamine 6G and Crystal Violet. In the presence of the Au film, the absorbance signal was 2–3 times higher than from an identically tapered uncoated fiber. The results confirm that the concept of SEIRAS can be implemented on an optical fiber probe, enabling enhanced signal detection in remote sensing applications.
关键词： surface enhancement,SEIRAS,sensing,optical fiber,Vis/NIR spectroscopy,gold
更新于2025-09-16 10:30:52
-
Deposition of Cu2ZnSnS4 films by doctor blade printing using a one-step microwave heated ink as an absorber layer for solar cells
摘要： Kesterite (Cu2ZnSnS4, CZTS) semiconductors are known as the most suitable compounds for the synthesis of absorber layers. These compounds are used in solar cells due to their high solar energy absorption coe?cient and ideal band gap. In the present work, the microwave-assisted process and doctor blade printing were used to prepare Cu2ZnSnS4 ?lms. To this aim, ink solution was used, which consisted of copper, zinc acetate, tin chloride and thiourea as copper, zinc, tin and sulfur precursors, respectively. Ethylene glycol was used as a non-toxic solvent. The CZTS ink was prepared using microwave heating for 10 min. The CZTS layers were printed on soda lime silica glass substrates and heat treated at 150, 200, 250, 300, and 350°C. The microstructure, phase analysis, morphology, optical properties, and absorption ratio of the samples were evaluated using X-ray di?raction analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, transmittance spectroscopy, ?eld emission scanning electron microscopy (FESEM), energy dispersive X-ray, and UV–Vis spectrophotometry. The formation of the Kesterite structure was con?rmed using X-ray di?raction and Raman spectroscopy. The FESEM micrographs and DLS (dynamic light scattering) revealed that the ?lms contained equated grains with the diameter range of 350–650 nm. According to the X-ray analysis and Raman spectrum, the highest crystallization and purity of the Kesterite phase as well as the best microstructure property and morphology (smooth spherical particles with good adhesion) of the CZTS ?lms were found in the synthesized specimen at 300°C. The band gap of the samples was measured to be about 1.5 eV using UV–Vis spectrophotometry.
关键词： Microwave heating process,UV–Vis spectrophotometry,Solar cell,CZTS ?lm
更新于2025-09-16 10:30:52
-
Plasmonic Response of Light-Activated, Nano-Gold Doped Polymers
摘要： Incorporation of metallic nanoparticles (NPs) in polymer matrix has been used to enhance and control dissolution and release of drugs, for targeted drug delivery, as antimicrobial agents, localized heat sources, and for unique optoelectronic applications. Gold NPs in particular exhibit a plasmonic response that has been utilized for photothermal energy conversion. Because plasmonic nanoparticles typically exhibit a plasmon resonance frequency similar to the visible light spectrum, they present as good candidates for direct photothermal conversion with enhanced solar thermal efficiency in these wavelengths. In our work, we have incorporated ~3-nm-diameter colloidal gold (Auc) NPs into electrospun polyethylene glycol (PEG) fibers to utilize the nanoparticle plasmonic response for localized heating and melting of the polymer to release medical treatment. Auc and Auc in PEG (PEG+Auc) both exhibited a minimum reflectivity at 522 nm or approximately green wavelengths of light under ultraviolet-visible (UV-Vis) spectroscopy. PEG+Auc ES fibers revealed a blue shift in minimum reflectivity at 504 nm. UV-Vis spectra were used to calculate the theoretical efficiency enhancement of PEG+Auc versus PEG alone, finding an approximate increase of 10 % under broad spectrum white light interrogation, and ~14 % when illuminated with green light. Auc enhanced polymers were ES directly onto resistance temperature detectors and interrogated with green laser light so that temperature change could be recorded. Results showed a maximum increase of 8.9 °C. To further understand how gold nanomaterials effect the complex optical properties of our materials, spectroscopic ellipsometry was used. Using spectroscopic ellipsometry and modeling with CompleteEASE? software, the complex optical constants of our materials were determined. The complex optical constant n (index of refraction) provided us with optical density properties related to light wavelength divided by velocity, and k (extinction coefficient) was used to show the absorptive properties of the materials.
关键词： spectroscopic ellipsometry,photothermal energy conversion,polyethylene glycol,metallic nanoparticles,plasmonic response,UV-Vis spectroscopy,gold NPs,electrospun fibers
更新于2025-09-16 10:30:52
-
Pressure effect on optical and structural properties of ZnMnO thin films grown by pulsed laser deposition
摘要： Zn0.95Mn0.05O thin films were deposited on Si substrate by pulsed laser ablation technique under different oxygen pressure. The structural and optical properties of the films were analyzed as a function of the oxygen gas pressure. The Mn concentration and the substrate temperature of the thin films were kept constant at 5 wt% and 200°C respectively. X-ray diffraction technique (XRD), atomic force spectroscopy (AFM), raman spectroscopy and UV-Vis were employed to characterize the optical properties and the crystalline structure of the films. The diffraction patterns revealed that the Mn0.05Zn0.95O thin films were polycrystalline with the wurtzite hexagonal structure of ZnO and highly oriented in c-axis direction, without any secondary phases. The average energy band gap of the films was evaluated around 3.23-3.56 eV. Raman spectrum showed E2 (low) mode of ZnO structure shifted to red and increased its FWHM.
关键词： Laser Ablation,X-ray Diffraction,UV-Vis Spectroscopy,Atomic Force Microscopy,Raman Spectroscopy
更新于2025-09-16 10:30:52
-
Alkali-metal-controlled changes of stability and NLO properties in ideal unscrewing process of double helix
摘要： Molecular machines were attractive for scientists due to their excellent dynamical properties and potential applications. Inspired by the feature of molecular machine, we designed an ideal unscrewing process of double-chain sexipyridine complex with four conformations and explored the variation of stability and optical properties. As a result, we found the double helices where the fragments bound by only weak π-π interaction had poor stability. Thus the conformation with stronger π-π interaction was more stable than others. But this could be changed by adding alkali metals, and different alkali metal atoms such as Li and Na could control the stability order because of their different atomic radii. For Li-doped molecules, Li-1 with tightly coiled strands was the most stable conformation. While for Na-doped molecules, Na-4 with unscrewed fragments was the most stable one. This mainly resulted from the intra-molecular interaction potential energy especially the interaction between metal and ligand. At the same time, the charge distribution showed corresponding variation. In the aspect of optical properties, the unscrewing process was followed by the variation of absorption intensity at about 500 nm in the UV–Vis absorption spectra because of the conformation change. Meanwhile, the first-order static hyperpolarizability (βtot) showed zigzag variation due to the change of frontier molecular orbital energy gap in the unscrewing process.
关键词： (un)screwing,NLO,Alkali metal doping,UV–Vis absorption,Double helix
更新于2025-09-16 10:30:52
-
Plasmonic Oligomers with Tunable Conductive Nanojunctions
摘要： Engineering plasmonic hot-spots is essential for applications of plasmonic nanoparticles. A particularly appealing route is to weld plasmonic nanoparticles together to form more complex structures sustaining plasmons with symmetries targeted to given applications. However, the control of the welding and subsequent hotspot characteristic is still challenging. Herein, we demonstrate an original method that connects gold particles to their neighbors by another metal of choice. We first assemble gold bipyramids in a tip-to-tip configuration, yielding short chains of variable length and grow metallic junctions in a second step. We follow the chain formation and the deposition of the second metal (i.e. silver or palladium) via UV/Vis spectroscopy and we map the plasmonic properties using electron energy loss spectroscopy. The formation of silver bridges leads to a huge redshift of the longitudinal plasmon modes into the mid-infrared region, while the addition of palladium results in a redshift accompanied by significant plasmon damping.
关键词： UV/Vis spectroscopy,Tunable conductive nanojunctions,Palladium,Plasmonic oligomers,Gold bipyramids,Electron Energy Loss Spectroscopy,Silver bridges
更新于2025-09-12 10:27:22
-
Determination of the bruise degree for cherry using Vis-NIR reflection spectroscopy coupled with multivariate analysis
摘要： Determination and classification of the bruise degree for cherry can improve consumer satisfaction with cherry quality and enhance the industry’s competiveness and profitability. In this study, visible and near infrared (Vis-NIR) reflection spectroscopy was used for identifying bruise degree of cherry in 350–2500 nm. Sampling spectral data were extracted from normal, slight and severe bruise samples. Principal component analysis (PCA) was implemented to determine the first few principal components (PCs) for cluster analysis among samples. Optimal wavelengths were selected by loadings of PCs from PCA and successive projection algorithm (SPA) method, respectively. Afterwards, these optimal wavelengths were empolyed to establish the classification models as inputs of least square-support vector machine (LS-SVM). Better performance for qualitative discrimination of the bruise degree for cherry was emerged in LS-SVM model based on five optimal wavelengths (603, 633, 679, 1083, and 1803 nm) selected directly by SPA, which showed acceptable results with the classification accuracy of 93.3%. Confusion matrix illustrated misclassification generally occurred in normal and slight bruise samples. Furthermore, the latent relation between spectral property of cherries in varying bruise degree and its firmness and soluble solids content (SSC) was analyzed. The result showed both colour, firmness and SSC were consistent with the Vis-NIR reflectance of cherries. Overall, this study revealed that Vis-NIR reflection spectroscopy integrated with multivariate analysis can be used as a rapid, intact method to determine the bruise degree of cherry, laying a foundation for cherry sorting and postharvest quality control.
关键词： LS-SVM,Vis-NIR reflection spectroscopy,cherry,bruise degree,multivariate analysis
更新于2025-09-12 10:27:22
-
Fabrication of Interconnected Plasmonic Spherical Silver Nanoparticles with Enhanced Localized Surface Plasmon Resonance (LSPR) Peaks Using Quince Leaf Extract Solution
摘要： Interconnected spherical metallic silver nanoparticles (Ag NPs) were synthesized in the current study using a green chemistry method. The reduction of silver ions to Ag NPs was carried out with low-cost and eco-friendly quince leaves. For the first time, it was confirmed that the extract solution of quince leaves could be used to perform green production of Ag NPs. Fourier transform infrared spectroscopy (FTIR) was conducted to identify the potential biomolecules that were involved in the Ag NPs. The results depicted that the biosynthesis of Ag NPs through the extract solution of quince leaf was a low-cost, clean, and safe method, which did not make use of any contaminated element and hence, had no undesirable effects. The majority of the peaks in the FTIR spectrum of quince leaf extracts also emerged in the FTIR spectrum of Ag NPs but they were found to be of less severe intensity. The silver ion reduction was elaborated in detail on the basis of the FTIR outcomes. In addition, through X-ray diffraction (XRD) analysis, the Ag NPs were also confirmed to be crystalline in type, owing to the appearance of distinct peaks related to the Ag NPs. The creation of Ag NPs was furthermore confirmed by using absorption spectrum, in which a localized surface plasmon resonance (LSPR) peak at 480 nm was observed. The LSPR peak achieved in the present work was found to be of great interest compared to those reported in literature. Field emission scanning electron microscopy (FESEM) images were used to provide the morphology and grain size of Ag NPs. It was shown from the FESEM images that the Ag NPs had interconnected spherical morphology.
关键词： FESEM study,FTIR study,XRD analysis,UV–Vis absorption,quince leave,silver nanoparticles
更新于2025-09-12 10:27:22
-
Synthesis of ZnO nanoparticles in polyvinyl alcohol solutions using laser assisted synthesis in solution (LASiS) method
摘要： ZnO nanoparticles are widely studied because of their superior properties so they are widely used in various applications. Structural modification with the right synthesis method is the key to getting superior properties. In this experiment, Laser Assisted Synthesis in Solution (LASiS) method was used to synthesize ZnO nanoparticles. The LASIS method was carried out using a metal plate Zn as a target placed in a solution of polyvinyl alcohol (PVA) with different concentrations, namely 1%, 2%, 3% and 4%. This laser ablation has caused a solution of gray colloidal ZnO nanoparticles. Different PVA concentrations do not affect the color of the produced ZnO nanoparticle solution. The properties and structure of ZnO nanoparticles were characterized using UV-Vis spectrophotometer, Zetasizer spectrometer, and Transmission Electron Microscopy (TEM). The UV visible absorbance spectrum shows the maximum absorption characteristics of ZnO nanoparticles observed at a wavelength of 344 nm. The maximum absorbance value rises by increasing the concentration of PVA and reaching the maximum value at a concentration of 3%. These ZnO nanoparticles have a size around 80 nm. TEM analysis shows that ZnO nanoparticles have a spherical shape and have good crystallinity based on SAED measurements. This property is due to the role of PVA in the synthesis process.
关键词： ZnO nanoparticles,polyvinyl alcohol,UV-Vis spectrophotometer,Zetasizer spectrometer,LASiS method,Transmission Electron Microscopy
更新于2025-09-12 10:27:22