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Interaction of Graphene Quantum Dots with Oligothiophene: A Comprehensive Theoretical Study
摘要： Graphene/polythiophene composites are widely used in a variety of optoelectronic devices and applications, e.g., as electrode materials in capacitors and solar cells, but the detailed molecular-level relationship between their structural and electronic properties is not well understood. We present a density functional theory study of these composites using model systems consisting of graphene nanosheets and nanoribbons sandwiched between oligothiophenes (up to 13 monomers in length). These systems are investigated by computing optical band gaps, UV-vis spectra, densities of states, and by analyzing noncovalent interactions in terms of the reduced density gradient. Frontier molecular orbital analysis reveals a significant decrease in the optical band gap upon increasing the concentration of graphene, which can be tuned by adjusting the proportion of graphene using larger nanoribbons. This finding has implications for device design in these materials.
关键词： UV-vis Spectra,Composites,Optical Band Gap,Graphene,Noncovalent Interactions,Density Functional Theory,Polythiophene
更新于2025-09-12 10:27:22
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New small organic molecules based on thieno[2,3-b]indole for efficient bulk heterojunction organic solar cells: a computational study
摘要： This study aims to evaluate the characteristics of novel organic D-π-A-π-D class small-molecules by using carefully the density functional theory, and time-dependent density functional theory calculations. Thedesigned sequence of (D-A) BHJ-1a to BHJ-4a in organic Bulk Heterojunction (BHJ) solar cells has been comprehensively analysed. Thiéno[2,3-b]indole (TI) has been used as donor, and Diketopyrrolopyrrole (DPP) as acceptor for all compounds. In order to improve the electronic, photovoltaic, and opticalproperties, we have substituted thiophene unit with furan, thieno[2,3-b]thiophene, thiazole and thiazolothiazole as π-bridge moieties. Thus, the result shows that the wise choice of the π-bridge units plays a significant role in improving Egap, producing a high bathochromic shift, and increasing VOC as well as a theoretical power conversion efficiency (PCE) over 7%. Interestingly, BHJ-4a with suitable π-bridge presents the optimal electronic properties with low band gap (1.870 eV) and high VOC (1.534 eV). Furthermore, we have modelled a Bulk heterojunction organic photovoltaic cells based on donor-PCBM complex in order to achieve the optimum Egap and VOC. Consequently, the obtained results provide a new way to design BHJ small molecule donors with higher power conversion efficiency.
关键词： BHJ organic solar cells,DFT,PCBM,UV–Vis,thiéno[2,3-b]indole
更新于2025-09-11 14:15:04
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Precipitation of Silver Nanoparticles in Borate Glasses by 1064?nm Nd:YAG Nanosecond Laser Pulses: Characterization and Dielectric Studies
摘要： This work aims to present a modern process to synthesis nanoparticles in a glassy matrix. Borate glasses doped by silver nitrate (AgNO3) via the melt annealing technique were irradiated by a (1064 nm wavelength) Nd:YAG (Neodymium–doped Yttrium Aluminum Garnet) laser to yeild precipitation of silver nanoparticles (AgNPs) in borate glasses. The characterization of the irradiated glasses was investigated using ultraviolet/visible (UV/Vis.), x-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM), ?eld emission-scanning electron microscopy (FE-SEM), and dielectric properties. XRD patterns depict the presence of sharp diffraction peaks at 111 and 200 planes that can be attributed to the precipitated AgNPs in the borate glass sample after laser irradiation. A signi?cant change in color was observed within the borate glass after laser irradiation, which was attributed to the appearance of surface plasmon resonance and con?rmed the presence of AgNPs in the borate glass. The morphological properties and the distribution of the observed AgNPs inside the sample were performed via HR-TEM and FE-SEM. The behavior of dielectric constant and dielectric loss progressively decreased as the frequency increased. The values of AC conductivity increased as the temperature of the borate glass matrix increased.
关键词： Borate,UV/Vis.,Nd:YAG,dielectric properties,AgNPs,XRD,FE-SEM,HR-TEM
更新于2025-09-11 14:15:04
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Reversibly Photoswitchable Dual-Color Fluorescence and Controlled Release Properties of Polymeric Nanoparticles
摘要： Here, we report a novel polymeric nanoparticle prepared by the self-assembly of amphiphilic copolymers containing a ?uorescent naphthalimide (NAPH) and a photochromic spiropyran (SP), which possesses reversibly photoswitchable dual-color ?uorescence and controlled release properties. The amphiphilic copolymers were synthesized by incorporating NAPH and SP into methyl ether poly(ethylene glycol)-poly(β-amino esters) (MPEG-PAE) via quaternization. The nanoparticles would change between yellow and purple reversibly upon UV and visible light irradiation because of the photoisomerization between SP and merocyanine (MC). The corresponding ?uorescence would be switched between green and orange-red reversibly upon blue light excitation through the ?uorescence resonance energy transfer from the excited NAPH to the photoisomerized MC. Meanwhile, the prepared spherical nanoparticles could be swollen under UV irradiation as the hydrophobic SP isomerized to hydrophilic MC; the nanoparticles could also be swollen under acidic conditions because of the protonation of the amino groups of PAE. Upon UV light irradiation and acidic stimulation, the cargoes, hydrophobic Coumarin 102, encapsulated in the nanoparticles would be released. The prepared nanoparticles, which exhibit not only excellent reversible dual-color ?uorescence properties but also prominent controlled release performance, will open up new possibilities for the combined application of ?uorescence imaging and controlled release.
关键词： naphthalimide,Coumarin 102,spiropyran,polymeric nanoparticles,photoswitchable,amphiphilic copolymers,acidic conditions,quaternization,self-assembly,FRET,UV/vis light irradiation,dual-color ?uorescence,MPEG-PAE,controlled release
更新于2025-09-11 14:15:04
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A Plasmonic Approach to Study Protein Interaction Kinetics through the Dimerization of Functionalized Ag Nanoparticles
摘要： Understanding the kinetics of protein interactions plays a key role in biology with significant implications for the design of analytical methods for disease monitoring and diagnosis in medical care, research and industrial applications. Herein, we introduce a novel plasmonic approach to study the binding kinetics of protein-ligand interactions following the formation of silver nanoparticles (Ag nps) dimers by UV-Vis spectroscopy that can be used as probes for antigen detection and quantification. to illustrate and test the method, the kinetics of the prototype biotin-streptavidin (Biot-StV) pair interaction was studied. controlled aggregates (dimers) of StV functionalized Ag nps were produced by adding stoichiometric quantities of gliadin-specific biotinylated antibodies (IgG-Biot). The dimerization kinetics was studied in a systematic way as a function of Ag NPs size and at different concentrations of IgG-Biot. The kinetics data have shown to be consistent with a complex reaction mechanism in which only the Ag NPs attached to the IgG-Biot located in a specific STV site are able to form dimers. These results help in elucidating a complex reaction mechanism involved in the dimerization kinetics of functionalized Ag nps, which can serve as probes in surface plasmon resonance-based bioassays for the detection and quantification of different biomarkers or analytes of interest.
关键词： biotin-streptavidin interaction,silver nanoparticles,dimerization,protein interaction kinetics,plasmonic approach,surface plasmon resonance,UV-Vis spectroscopy
更新于2025-09-11 14:15:04
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Application of Spectroscopic UV-Vis and FT-IR Screening Techniques Coupled with Multivariate Statistical Analysis for Red Wine Authentication: Varietal and Vintage Year Discrimination
摘要： One of the most important issues in the wine sector and prevention of adulterations of wines are discrimination of grape varieties, geographical origin of wine, and year of vintage. In this experimental research study, UV-Vis and FT-IR spectroscopic screening analytical approaches together with chemometric pattern recognition techniques were applied and compared in addressing two wine authentication problems: discrimination of (i) varietal and (ii) year of vintage of red wines produced in the same oenological region. UV-Vis and FT-IR spectra of red wines were registered for all the samples and the principal features related to chemical composition of the samples were identi?ed. Furthermore, for the discrimination and classi?cation of red wines a multivariate data analysis was developed. Spectral UV-Vis and FT-IR data were reduced to a small number of principal components (PCs) using principal component analysis (PCA) and then partial least squares discriminant analysis (PLS-DA) and linear discriminant analysis (LDA) were performed in order to develop qualitative classi?cation and regression models. The ?rst three PCs used to build the models explained 89% of the total variance in the case of UV-Vis data and 98% of the total variance for FR-IR data. PLS-DA results show that acceptable linear regression ?ts were observed for the varietal classi?cation of wines based on FT-IR data. According to the obtained LDA classi?cation rates, it can be a?rmed that UV-Vis spectroscopy works better than FT-IR spectroscopy for the discrimination of red wines according to the grape variety, while classi?cation of wines according to year of vintage was better for the LDA based FT-IR data model. A clear discrimination of aged wines (over six years) was observed. The proposed methodologies can be used as accessible tools for the wine identity assurance without the need for costly and laborious chemical analysis, which makes them more accessible to many laboratories.
关键词： chemometrics,FT-IR,wine authentication,spectroscopic techniques,UV-Vis
更新于2025-09-11 14:15:04
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Molecular origin of photostability for fluorene-based donor–acceptor type photovoltaic polymers
摘要： Quantitative analyses of photodegradation for three fluorene-based photovoltaic polymers, poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4’,7’-di-2-thienyl-2’,1’,3’-benzothiadiazole)] (APFO3), polyfluorene (PFO), and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) were conducted to understand the molecular origin of photostability for polymers. The Fourier transform infrared (FT-IR) spectra of polymer thin-films varied by irradiating white light at 100 mW?cm-2 irrespective of their molecular architectures. The absorption peaks corresponding to alkyl side chains in a fluorene unit decreased, whereas those for polymers that did not comprise carbonyl groups increased. This spectral variation indicates that alkyl side chains in the fluorene unit decompose when the molecular structure of fluorene varies to that of fluorenone. The reaction rate constant of formation of C=O bond for APFO3 was 1.64×10-5 s-1, lower than PFO (7.59×10-5 s-1) and F8BT (2.64×10-5 s-1), under light irradiation at 30 ?C. The photostability of the polymers improves by designing a donor–acceptor type molecular architecture—incorporating photostable electron deficient benzothiadiazole units with photo-unstable fluorene units.
关键词： fluorene-based,photostability,FT-IR,donor–acceptor,UV-vis,photovoltaic polymers
更新于2025-09-11 14:15:04
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Constructing g-C3N4 quantum dots modified g-C3N4/GO nanosheet aerogel for UV-Vis-NIR driven highly efficient photocatalytic H2 production
摘要： The development of ultraviolet to near-infrared (UV-Vis-NIR) responsive photocatalysts offers a unique opportunity for the full use of solar energy to solve the energy and the environmental problems. Here, successful preparation of a three-dimensional (3D) porous photocatalyst of graphitic carbon nitride quantum dot (CNQDs) modified g-C3N4/graphene oxide composite aerogel (CNGO/CNQDs) via hydrothermal and vacuum injection method was reported. In this unique ternary 3D photocatalyst, graphene oxide could improve the separation of photogenerated electrons and holes and promote the charge separation, while the aerogel’s 3D network structure provided a rich active site. Simultaneously, due to the appropriate up-conversion performance of the nitrogen carbide quantum dots, CNGO/CNQDs achieved a light response from ultraviolet (UV) to near-infrared (NIR). These properties endow it with a good photocatalytic performance. The hydrogen production efficiency of CNGO/CNQDs reached 1231 mmol h?1, which was 16 times more than that of matrix material. In addition, the apparent quantum yields (AQY) of CNGO/CNQDs at wavelengths of 420 nm and 700 nm were 13% and 0.116%, respectively.
关键词： Photocatalytic,Quantum dots,3D,UV-Vis-NIR driven,g-C3N4
更新于2025-09-11 14:15:04
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Synthesis of gold nanoparticles by pulsed laser-assisted reduction of aqueous gold precursor
摘要： In this paper, colloidal gold nanoparticles (GNPs) were synthesized by Nd:YAG (λ = 1064 nm) pulsed laser-assisted reduction (PLAR) of aqueous [AuCl4]?. In this process, during laser ablation of a Mo target in DI water, a [AuCl4]? precursor solution was being added dropwise in situ. UV–Vis absorption spectra showed distinct plasmonic absorption bands at 209 and 530 nm corresponding to Mo nanoparticles (NPs) and GNPs, respectively. Furthermore, no significant conversion for [AuCl4]? was found when it was added to aged Mo NPs or when it was irradiated in the lack of the Mo target. Using transmission electron microscope (TEM) images, it was found that precursor concentration and laser-ablation time can affect the population or size of GNPs. In PLAR with a small amount of KI solution in water, the GNPs size increases to ~ 50 nm via an iodine-induced particle fusion mechanism. The reduction mechanism was discussed based on metastable species intercation, producing the cavitation bubble during laser ablation.
关键词： Mo target,Nd:YAG laser,TEM,UV–Vis absorption,Pulsed laser-assisted reduction,Gold nanoparticles,KI solution
更新于2025-09-11 14:15:04
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Performance Enhancement of Chitosan Filled Silver Vanadate Nano-rods
摘要： Silver vanadate nanorods synthesized via chemical precipitation route at room temperature were characterized using UV/Vis. optical electronic spectra, fourier transform infrared (FTIR) spectroscopy, transmission and scanning electron microscopy (TEM, SEM), Zeta potential and X-ray diffraction (XRD). XRD indicates the presence of both β and α phases of silver vanadate. Chitosan samples filled with pre-calculated amounts of synthesized silver vanadate nano-rods were prepared via ordinary casting route. XRD of the prepared polymeric samples reveals amorphous nature and indicating a homogenous distribution of inorganic filler within the matrix without any tendency for crystallization. FTIR shows maintenance of chitosan characteristic bands in all samples. Optical energy gap for both direct and indirect transitions generally indicates a gradual decrease with increasing inorganic filler content. The biological activity against two-gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis), two gram-negative bacteria (Escherichia coli, Pseudomonas aeuroginosa) in addition to one fungus (Candida albicans) were also studied and correlated with both optical energy gap and nanoparticle dopant concentration.
关键词： UV/Vis.,Zeta Potential,Silver vanadate,FTIR,Chitosan,XRD
更新于2025-09-11 14:15:04