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Density, Structure, and Stability of Citrate <sup>3–</sup> and H <sub/>2</sub> Citrate <sup>–</sup> on Bare and Coated Gold Nanoparticles
摘要： We simulate the packing of citrate3– and H2citrate– onto gold nanoparticles (AuNPs) to understand how citrate anions cap and stabilize AuNPs. We determine the molecular configurations of citrate on 4, 6, and 8 nm AuNP surfaces as a function of charge state and packing density and find that both the distribution of configurations and maximum packing density are independent of AuNP size. A combination of molecular dynamics simulations and in situ Fourier transform infrared spectroscopy (FTIR) is employed to compare the molecular configurations, stability, and density of citrate on 4 nm citrate-coated (cit-AuNPs) and within polycation-wrapped 4 nm cit-AuNPs. FTIR experiments indicate the presence of H2citrate– within polycation-wrapped cit-AuNPs with coordination between the H2citrate– layer and polycation layer in agreement with simulations. Intermolecular hydrogen bonding between terminal carboxylic-acid groups of H2citrate– stabilizes the anionic layer at the interface between cit-AuNPs and adsorbing charged molecules. The calculated total density of H2citrate– on AuNPs decreases from 3.3 × 10-10 mol/cm2 to 3.0 × 10-10 mol/cm2 upon adsorption of a polycation due to some displacement of dangling H2citrate– hydrogen bonded to the surface-bound layer. The density of the surface-bound layer is consistently 2.8 × 10-10 mol/cm2 with and without polycation adsorption. We provide all-atom level insight into the distribution and organization of experimentally derived binding modes of citrate on bare and coated cit-AuNPs. The citrate density and surface charge density are determined for all-atom and coarse-grained modeling of cit-AuNPs, their functionalization, and transformations in complex environments.
关键词： polycation adsorption,gold nanoparticles,FTIR spectroscopy,citrate,molecular dynamics simulations
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Study on Photoemission of Patterned Carbon Nanotubes Modified with Gold Nanoparticles
摘要： Employing the edge effect and localized surface plasmon resonance effect, an enhanced photoemission is obtained from a carbon nanotube (CNT) arrays modified with gold nanoparticles. Compared with the unpatterned CNTs, the quantum efficiency of patterned CNTs is improved from 3.69×10-6 to 1.85×10-5. After modification with gold nanoparticles, the quantum efficiency of patterned CNTs is further raised to 4.98×10-5. This work makes CNTs as a promising material for the high stability and high efficiency photocathode.
关键词： Patterning,Photocathode,Gold nanoparticles,CNTs
更新于2025-09-23 15:21:21
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Augmented tumor accumulation and photothermal ablation using gold nanoparticles with a particular cellular entry orientation
摘要： Gold nanoparticles with various functionalities have served as potential tools in nanotechnology for tumor ablation. In this work, we seek to design and develop gold nanoparticle with poly(ethylene glycol)-containing dopamine (hereafter termed as AuND), and to synthesize the AuND with one-sided Tat peptide expression (OT@AuND). We demonstrate the tumor cell-targeting ability on the basis of anti-nonspecific cell binding of OT@AuND and determine how the chemically modified gold nanoparticle–based product affects photothermal tumor therapy in vitro and in vivo. The OT@AuND with a particular cellular entry orientation–induced delayed endocytosis, which is advantageous for enhanced permeability and retention effect-based tumor accumulation. This is because the slower cellular interaction of OT@AuND allows it to have the time to be transported to and bind to the tumor site. In tumor cell lines, OT@AuND showed a lower cellular uptake than gold nanoparticles with full-sided Tat peptide expression (FT@AuND) in the early period (after its in vitro and in vivo administration), but the cellular internalization rate of OT@AuND caught up with that of FT@AuND in the late period. Importantly, the delayed cellular internalization feature of OT@AuND resulted in efficient tumor accumulation in tumor-bearing mice, because the time interval provided OT@AuND more chances not to bind to any cells, but to enter tumor cells, leading to selective photothermal tumor ablation. These data suggest that gold nanoparticles with a particular cellular entry orientation can be further explored as a potential photothermal therapeutic agent and as a strategy to treat tumors.
关键词： photothermal tumor ablation,cellular entry orientation,Gold nanoparticles,one-sided Tat peptide,enhanced permeability and retention
更新于2025-09-23 15:21:21
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<i>In situ</i> structural kinetics of picosecond laser-induced heating and fragmentation of colloidal gold spheres
摘要： Fragmentation of colloidal 54 nm gold nanoparticles by picosecond laser pulses is recorded by time-resolved X-ray scattering, giving access to structural dynamics down to a 80 ps resolution. Lattice temperature and energy dissipation have been quantified to verify that the maximum applied fluence of 1800 J m?2 heats up the particles close to boiling. Already within 30 ns, particles with significantly lower particle sizes of 2 to 3 nm are detected, which hints towards an ultrafast process either by a thermal phase explosion or Coulomb instability. An arrested growth is observed on a microsecond time scale resulting in a final particle size of 3–4 nm with high yield. In this context, the fragmentation in a NaCl/NaOH solution seems to limit growth by electrostatic stabilization of fragments, whereas it does not modify the initial product sizes. The laser-induced fragmentation process is identified as a single-step, instantaneous reaction.
关键词： Coulomb instability,fragmentation,thermal phase explosion,time-resolved X-ray scattering,picosecond laser pulses,gold nanoparticles
更新于2025-09-23 15:21:01
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Kinetics of molecular decomposition under irradiation of gold nanoparticles with nanosecond laser pulsesa??A 5-Bromouracil case study
摘要： Laser illuminated gold nanoparticles (AuNPs) efficiently absorb light and heat up the surrounding medium, leading to versatile applications ranging from plasmonic catalysis to cancer photothermal therapy. Therefore, an in-depth understanding of the thermal, optical, and electron induced reaction pathways is required. Here, the electrophilic DNA nucleobase analog 5-Bromouracil (BrU) has been used as a model compound to study its decomposition in the vicinity of AuNPs illuminated with intense ns laser pulses under various conditions. The plasmonic response of the AuNPs and the concentration of BrU and resulting photoproducts have been tracked by ultraviolet and visible (UV–Vis) spectroscopy as a function of the irradiation time. A kinetic model has been developed to determine the reaction rates of two parallel fragmentation pathways of BrU, and their dependency on laser fluence and adsorption on the AuNP have been evaluated. In addition, the size and the electric field enhancement of the decomposed AuNPs have been determined by atomic force microscopy and finite domain time difference calculations, respectively. A minor influence of the direct photoreaction and a strong effect of the heating of the AuNPs have been revealed. However, due to the size reduction of the irradiated AuNPs, a trade-off between laser fluence and plasmonic response of the AuNPs has been observed. Hence, the decomposition of the AuNPs might be limiting the achievable temperatures under irradiation with several laser pulses. These findings need to be considered for an efficient design of catalytic plasmonic systems.
关键词： gold nanoparticles,plasmonic catalysis,5-Bromouracil,laser irradiation,photothermal therapy
更新于2025-09-23 15:21:01
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Enhanced efficiency in dye-sensitized solar cell by localized surface plasmon resonance effect of gold nanoparticles
摘要： Strong localized surface plasmon resonance (LSPR) ˉeld, which is generated from gold nanoparticles, may enhance photons absorption of dyes in dye-sensitized solar cells (DSSCs), resulting in the improvement of their power conversion e±ciency (PCE). In this paper, we report the incorporation of oleylamine capped gold nanoparticles (AuOA NPs) into the N-719 dye layer in DSSCs. The cells were prepared by varying the weight percentage of AuOA NPs with respect to the dye weight in dye solutions. The dye solutions containing 1.44 wt.%, 1.92 wt.% and 2.4 wt.% of AuOA NPs exhibited an enhancement in their absorption spectra in the UV-Visible range, which may be the result of the excitation of localized SPR. The J (cid:1) V characteristics of those DSSCs show an enhancement in their photocurrent along with their PCE, from 4.18% to 5.14% for the cells made from the dye solutions without AuOA and with addition of 2.4 wt.% of AuOA, respectively. This improvement is due to the enhancement of light absorption and hence charge carrier generation by the Plasmonic wave generated by AuOA NPs through the LSPR phenomenon.
关键词： gold nanoparticles,impedance spectroscopy,localized surface plasmon resonance,J (cid:1) V characteristics,Dye-sensitized solar cells
更新于2025-09-23 15:21:01
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Additive-controlled synthesis of monodisperse single crystalline gold nanoparticles: interplay of shape and surface plasmon resonance
摘要： We introduce a three-step seed-mediated synthesis for single crystalline gold nanoparticles (Au NPs) stabilized by hexadecylpyridinium chloride (CPC) in variable sizes with an adjustable ratio of the cubic and octahedral facets. The effect of KBr and ascorbic acid (AA) on shape and growth kinetics is systematically investigated. The kinetic data were evaluated using the minimalistic Finke-Watzky autocatalytic two-step mechanism, which allows to estimate the rate constants of the “pseudoelementary” reactions. The proposed surface-mediated mechanism of reduction of gold ions and Au NPs growth allows to explain the effect of gradual increase of bromide ion concentration on switching the Au NPs morphology from cubic to octahedral. The plasmonic properties of single particles of different facetings and their assemblies are investigated.
关键词： gold nanoparticles,Finke-Watzky mechanism,plasmonic properties,seed-mediated synthesis,surface plasmon resonance
更新于2025-09-23 15:21:01
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Controlled synthesis of gold nanoparticles in copolymers nano-molds by x-ray radiolysis
摘要： We show by x-ray and neutron small angle scattering that gold nanoparticles with controlled sizes and morphologies can be obtained by the metallic reduction of AuCl4- ions trapped in 3D organic molds by x-ray radiolysis. The molds are spherical frozen micelles of polystyrene‐b‐poly(dimethylaminoethyl methacrylate) (PS‐b‐PDMAEMA) block copolymer in acidic aqueous solution with a PS spherical core surrounded by a corona of PDMAEMA chains in good solvent. The behavior of micelles is controlled by the [AuCl4-]/[DMAEMA] ratio RAuCl4-/DMAEMA. At low gold concentration, AuCl4- ions condense on the positively charged DMAEMA moieties without changing the behavior of the PDMAEMA chains. At intermediate gold concentration, the ions induce a progressive contraction of the corona’s chains and dehydration of micelles. At large gold concentration, the corona becomes a fully dry phase loaded with gold ions, which induces micelle aggregation. The radiolysis of the solution by an intense x-ray beam produces different types of gold nanoparticles with respect to RAuCl4-/DMAEMA and irradiation time. At RAuCl4-/DMAEMA = 0.033, the irradiation produces in a first step gold clusters in the micelle corona which in a second step merge to form nanoparticles of a similar size to the one of the micelle. Conversely, at RAuCl4-/DMAEMA = 0.33, micelles do not operate as templates but only as nucleation zones and large nanoparticles grow outside the micelles.
关键词： gold nanoparticles,copolymers template,x-ray radiolysis,small angle scattering,synthesis
更新于2025-09-23 15:21:01
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Nanostructures for Cancer Therapy || Dose enhancement effect in radiotherapy: adding gold nanoparticles to tumor in cancer treatment
摘要： The rationale of radiation dose enhancement due to gold nanoparticle addition in radiotherapy is revealed from the basic particle interactions to Monte Carlo simulation. Our review of different radiobiological studies on Monte Carlo, cell line, and preclinical model confirms that cancer cell kill definitely benefits from the dose enhancement when gold nanoparticles were added. Moreover, such dose enhancement depends on the size, shape, and concentration of the gold nanoparticle, as well as the type and energy of the radiation beams. It is concluded that adding gold nanoparticles to the tumor can enhance both the dose and contrast at the target in radiotherapy.
关键词： radiotherapy,cancer treatment,Monte Carlo simulation,gold nanoparticles,dose enhancement
更新于2025-09-23 15:21:01
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Highly sensitive and selective sensor probe using glucose oxidase/gold nanoparticles/graphene oxide functionalized tapered optical fiber structure for detection of glucose
摘要： A tapered optical fiber structure based glucose sensor using graphene oxide (GO) and gold nanoparticles (AuNPs) is presented in this study. The waist diameter and length of the taper region are 25 μm and 6 mm, respectively. The taper region was created to expose the evanescent waves to the cladding boundaries and to get interact with the external medium. Further, the cladding of tapered region is covered with GO and AuNPs to increase the biocompatibility of sensor and to initiate the phenomenon of localized surface plasmon resonance (LSPR), respectively. The synthesized GO and AuNPs show the good absorbance properties at the peak absorbance wavelengths of 230 nm and 519 nm, respectively. The characterization of synthesized nanomaterials was done by using UV–vis spectrophotometer and TEM. The characterization of nanomaterial coated fiber probe was done by using SEM and SEM-EDS. The specificity of developed sensor probe is enhanced by immobilizing them with the glucose oxidase enzyme, that oxidized only in the presence of glucose solution. The attained results show that the developed sensor model is highly sensitive for the detection of glucose concentrations in human bodies with a sensitivity of 1.06 nm/mM in the linear range of 0 mM–11 mM with the autocorrelation accuracy of 0.9386.
关键词： Localized surface plasmon resonance,Glucose oxidase,Tapered optical fiber,Gold nanoparticles,Glucose,Graphene oxide
更新于2025-09-23 15:21:01