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Enhanced Broadband and Harmonic Upconversion from Coupled Semiconductor and Metal Nanoparticle Films
摘要： The enhancement of the nonlinear optical properties of hybrid nanoparticle ?lms by coupling between metallic and plasmonic semiconducting nanoparticles is shown. A heterostructure comprising CuS and Au nanoparticle ?lms separated by a thin layer of insulating ligands enhanced the yield of second-harmonic light by a factor of 3.3 compared with the sum of the constituent nanoparticles on their own. Heterostructures were fabricated with scalable solution-processing techniques that can create devices of arbitrary geometry. In addition to harmonic generation, the multiple-photon photoluminescence response of Au, CuS, and heterostructured ?lms is also explored.
关键词： plasmon,heterostructure,copper sul?de nanoparticle,second-harmonic generation,gold nanoparticle,multiphoton photoluminescence,nonlinear optical material
更新于2025-09-23 15:19:57
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Plasmonic nanoparticles assemblies templated by helical bacteria and resulting optical activity
摘要： Plasmonic nanoparticles (NPs) adsorbing onto helical bacteria can lead to formation of NP helicoids with micron scale pitch. Associated chiroptical effects can be utilized as bioanalytical tool for bacterial detection and better understanding of the spectral behavior of helical self-assembled structures with different scales. Here, we report that enantiomerically pure helices with micron scale of chirality can be assembled on Campylobacter jejuni, a helical bacterium known for severe stomach infections. These organisms have right-handed helical shapes with a pitch of 1–2 microns and can serve as versatile templates for a variety of NPs. The bacteria itself shows no observable rotatory activity in the visible, red, and near-IR ranges of electromagnetic spectrum. The bacterial dispersion acquires chiroptical activity at 500–750 nm upon plasmonic functionalization with Au NPs. Finite-difference time-domain simulations confirmed the attribution of the chiroptical activity to the helical assembly of gold nanoparticles. The position of the circular dichroism peaks observed for these chiral structures overlaps with those obtained before for Au NPs and their constructs with molecular and nanoscale chirality. This work provides an experimental and computational pathway to utilize chiroplasmonic particles assembled on bacteria for bioanalytical purposes.
关键词： bacteria,simulation,C. jejuni,circular dichroism,plasmonic,mesoscale,gold nanoparticle,biotechnology
更新于2025-09-23 15:19:57
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Reconfigurable Plasmonic Nanostructures Controlled by DNA Origami
摘要： Precise surface functionalization and reconfigurable capability of nanomaterials are essential to construct complex nanostructures with specific functions. Here we show the assembly of a reconfigurable plasmonic nanostructure, which executes both conformational and plasmonic changes in response to DNA strands. In this work, different sized gold nanoparticles(AuNPs) were arranged site-specifically on the surface of a DNA origami clamp nanostructure. The opening and closing of the DNA origami clamp could be precisely controlled by a series of strand displacement reactions. Therefore, the patterns of these AuNPs could be switched between two different configurations. The observed plasmon band shift indicates the change of the plasmonic interactions among the assembled AuNPs. Our study achieves the construction of reconfigurable nanomaterials with tunable plasmon ic interactions, and will enrich the toolbox of DNA-based functional nanomachinery.
关键词： DNA origami,Reconfigurable nanostructure,Gold nanoparticle,Plasmonic nanostructure
更新于2025-09-23 15:19:57
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Fluorometric virus detection platform using quantum dots-gold nanocomposites optimizing the linker length variation
摘要： In this study, a tunable biosensor using the localized surface plasmon resonance (LSPR), controlling the distance between fluorescent CdZnSeS/ZnSeS quantum dots (QDs) and gold nanoparticles (AuNPs) has been developed for the detection of virus. The distance between the AuNPs and QDs has been controlled by a linkage with a peptide chain of 18 amino acids. In the optimized condition, the fluorescent properties of the QDs have been enhanced due to the surface plasmon effect of the adjacent AuNPs. Successive virus binding on the peptide chain induces steric hindrance on the LSPR behavior and the fluorescence of QDs has been quenched. After analyzing all the possible aspect of the CdZnSeS/ZnSeS QD-peptide-AuNP nanocomposites, we have detected different concentration of influenza virus in a linear range of 10?14 to 10?9 g?mL?1 with detection limit of 17.02?fg?mL?1. On the basis of the obtained results, this proposed biosensor can be a good alternative for the detection of infectious viruses in the various range of sensing application.
关键词： Quantum dots,Localized surface plasmon resonance,Biosensor,Peptide,Influenza virus,Gold nanoparticle
更新于2025-09-23 15:19:57
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Polysaccharide enabled biogenic fabrication of pH??sensing fluorescent gold nanoclusters as a biocompatible tumor imaging probe
摘要： A biocompatible natural polysaccharide (PSP001) isolated from the fruit rind of Punica granatum was conjugated with L-cysteine (Y) to be used as a skeleton for the fabrication of fluorescent gold nanoclusters (AuNCs) represented as PSP-Y-AuNCs. With an average size of ~ 6 nm, PSP-Y-AuNCs demonstrated high quantum yield (31%), with a pH-sensitive fluorescence emission behavior. An emission maximum of 520 nm was obtained at acidic pH, which was blue shifted with increasing pH. This feature provides the possibilities for accurate ratiometric pH imaging. The PSP-Y-AuNCs not only demonstrated excellent biocompatibility with cancer cells and isolated peripheral lymphocytes and red blood cells but also demonstrated to be an active molecular imaging probe with appealing cellular uptake efficiency. The investigations with BALB/c mice further confirmed the non-toxic nature and in vivo imaging potential of the AuNCs. Estimation of the bio-distribution on solid tumor bearing syngeneic murine models revealed a tumor-targeted enhanced fluorescence emission pattern which is attributed to the pH responsive fluorescence behavior and the acidic microenvironment of the tumor. These findings were further confirmed with an impressive tumor accumulation pattern displayed in a xenograft of human cancer bearing nude mice. On account of their impressive biocompatibility and photophysical features, PSP-Y-AuNCs can exploited for the real-time fluorescence imaging of cancer tissues.
关键词： Polysaccharide,Tumor,pH ratiometry,Biocompatibility,In vivo imaging,Nanocluster,Fluorescence,Punica granatum,Gold nanoparticle
更新于2025-09-23 15:19:57
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Colorimetric and dark-field microscopic determination of cadmium(II) using unmodified gold nanoparticles and?based on the formation of glutathione-cadmium(II) complexes
摘要： A colorimetric approach is presented for the determinaton of cadmium(II) using unmodified gold nanoparticles (AuNPs) as a colorimetric probe. The assay is based on AuNP aggregation that is induced by the complexes formed between Cd(II) and glutathione (GSH) in a concentrated solution of NaCl. Unmodified AuNPs are known to aggregate in high-salt medium, but GSH can prevent aggregation. In the presence of Cd(II), it will bind GSH, and this will cause the AuNPs to aggregate as indicated by yellow and red dots under dark-field microscopy observation and the formation of a blue coloration. By monitoring the intensity change of AuNPs (as a ratio of absorbances at 600 and 520 nm), Cd(II) can be quantified with a linear response in the 17 pM to 16.7 nM concentration range and a detection limit of 4.3 pM. The method was successfully applied to the determination of Cd(II) in spiked lake water by the standard addition mode, and the detection limit is 4.5 pM.
关键词： Microscopy,Yellow and red dots,Lake water,Glutathione,Ratiometric detection,Cadmium ion,Gold nanoparticle aggregation
更新于2025-09-23 15:19:57
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Co-ordinated Split Aptamer Assembly and Disassembly on Gold Nanoparticle for Functional Detection of HIV-1 Tat
摘要： Human immunodeficiency virus (HIV) is a life threatening, weakens the immune system upon infection, thus ultimately resulting in the fatal health issues. This situation necessitates the generation of different strategies for HIV detection. HIV-1 Tat, a transactivator of HIV gene expression, was chosen in this study as the target of a non-functional split aptamer. Implementation of split aptamer has been demonstrated in this work for colorimetric detection of HIV-1 Tat. An unmodified gold nanoparticle (GNP)-based colorimetric assay was used for the visible detection of the proof, displays color transitions from red to purple in relation to the dose-dependency of HIV-1 Tat against the split aptamer in ionic solutions. The visible color transition was characterized using UV-Vis spectrophotometer showing spectrum shift and supported by Scanning Electron Microscopy observation. With addition of sodium chloride, the color of the solution started to change to purple and spectrum started to shift to higher wavelength due to aggregation at HIV-1 Tat concentration as low as 10 nM. Specificity test was conducted with duplexed split aptamer and HIV-1 p24 has shown slight color changes. With HIV-1 Nef, GNP solution retains the color similar to the control, which indicated the specific split aptamer interaction to HIV-1 Tat.
关键词： Colorimetry,HIV-1 Tat,Gold nanoparticle,Split aptamer
更新于2025-09-23 15:19:57
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Quantitative analyses of amount and localization of radiosensitizer gold nanoparticles interacting with cancer cells to optimize radiation therapy
摘要： Previous studies showed that gold nanoparticles (AuNPs) are useful radiosensitizers which optimize radiation therapy under low-dose radiation. However, the mechanisms of AuNP radiosensitization, including the amount and localization of the AuNPs interacting with cancer cells, has not yet been quantified. To answer these questions, we prepared AuNPs conjugated with anti-human epidermal growth factor receptor type 2 (HER2) antibody via polyethylene glycol (PEG) chains (AuNP-PEG-HER2ab). AuNP-PEG-HER2ab specifically bound to the HER2-expressing cancer cells and entered the cells via endocytosis. Whether endocytosis of AuNP-PEG-HER2ab occurred had no effect on radiosensitization efficacy by AuNP-PEG-HER2ab in vitro. The radiosensitization efficacy in vitro depended on dose of AuNP-PEG-HER2ab or dose of X-ray. Moreover, AuNP-PEG-HER2ab administrated into tumor-bearing mice was localized to both the periphery of the tumor tissue and near the nuclei in cancer cells in tumor deep tissue. The localization of AuNP-PEG-HER2ab in tumor tissues was important factors for in vivo powerful radiosensitization efficacy.
关键词： Radiation therapy,Radiosensitizer,Low-dose radiation,Gold nanoparticle,HER2
更新于2025-09-23 15:19:57
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Anti-Stokes Emission from Hot Carriers in Gold Nanorods
摘要： The origin of light emission from plasmonic nanoparticles has been strongly debated lately. It is present as the background of surface enhanced Raman scattering, and, despite the low yield, has been used for novel sensing and imaging application because of its photostability. While the role of surface plasmons as an enhancing antenna is widely accepted, the main controversy regarding the mechanism of the emission is its assignment to either radiative recombination of hot carriers (photoluminescence) or electronic Raman scattering (inelastic light scattering). We have previously interpreted the Stokes shifted emission from gold nanorods as the Purcell effect enhanced radiative recombination of hot carriers. Here we specifically focused on the anti-Stokes emission from single gold nanorods of varying aspect ratios with excitation wavelengths below and above the inter-band transitions threshold while still employing continuous wave lasers. Analysis of the intensity ratios between Stokes and anti-Stokes emission yields temperatures that can only be interpreted as originating from the excited electron distribution and not a thermally equilibrated phonon population despite not using pulsed laser excitation. Consistent with this result as well as previous emission studies using ultrafast lasers, the power-dependence of the upconverted emission is nonlinear and gives the average number of participating photons as a function of emission wavelength. Our findings thus show that hot carriers and photoluminescence play a major role in the upconverted emission.
关键词： surface plasmon resonance,anti-Stokes photoluminescence,interband transition,intraband transition,hot electron temperature,gold nanoparticle
更新于2025-09-19 17:15:36
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Electrochemical Impedance Characterization of Cell Growth on Reduced Graphene Oxide–Gold Nanoparticles Electrodeposited on Indium Tin Oxide Electrodes
摘要： The improved binding ability of graphene–nanoparticle composites to proteins or molecules can be utilized to develop new cell-based assays. In this study, we fabricated reduced graphene oxide–gold nanoparticles (rGO-AuNP) electrodeposited onto a transparent indium tin oxide (ITO) electrode and investigated the feasibility of the electrochemical impedance monitoring of cell growth. The electrodeposition of rGO–AuNP on the ITO was optically and electrochemically characterized in comparison to bare, rGO-, and AuNP-deposited electrodes. The cell growth on the rGO–AuNP/ITO electrode was analyzed via electrochemical impedance measurement together with the microscopic observation of HEK293 cells transfected with a green fluorescent protein expression vector. The results showed that rGO–AuNP was biocompatible and induced an increase in cell adherence to the electrode when compared to the bare, AuNP-, or rGO-deposited ITO electrode. At 54 h cultivation, the average and standard deviation of the saturated normalized impedance magnitude of the rGO–AuNP/ITO electrode was 3.44 ± 0.16, while the value of the bare, AuNP-, and rGO-deposited ITO electrode was 2.48 ± 0.15, 2.61 ± 0.18, and 3.01 ± 0.25, respectively. The higher saturated value of the cell impedance indicates that the impedimetric cell-based assay has a broader measurement range. Thus, the rGO–AuNP/ITO electrode can be utilized for label-free and real-time impedimetric cell-based assays with wider dynamic range.
关键词： gold nanoparticle,graphene oxide,electrochemical impedance spectroscopy,cell-based assay,electrodeposition
更新于2025-09-19 17:15:36