- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Interfacing CRYSTAL/AMBER to Optimize QM/MM Lennard–Jones Parameters for Water and to Study Solvation of TiO2 Nanoparticles
摘要： Metal oxide nanoparticles (NPs) are regarded as good candidates for many technological applications, where their functional environment is often an aqueous solution. The correct description of metal oxide electronic structure is still a challenge for local and semilocal density functionals, whereas hybrid functional methods provide an improved description, and local atomic function-based codes such as CRYSTAL17 outperform plane wave codes when it comes to hybrid functional calculations. However, the computational cost of hybrids are still prohibitive for systems of real sizes, in a real environment. Therefore, we here present and critically assess the accuracy of our electrostatic embedding quantum mechanical/molecular mechanical (QM/MM) coupling between CRYSTAL17 and AMBER16, and demonstrate some of its capabilities via the case study of TiO2 NPs in water. First, we produced new Lennard–Jones (LJ) parameters that improve the accuracy of water–water interactions in the B3LYP/TIP3P coupling. We found that optimizing LJ parameters based on water tri- to deca-mer clusters provides a less overstructured QM/MM liquid water description than when fitting LJ parameters only based on the water dimer. Then, we applied our QM/MM coupling methodology to describe the interaction of a 1 nm wide multilayer of water surrounding a spherical TiO2 nanoparticle (NP). Optimizing the QM/MM water–water parameters was found to have little to no effect on the local NP properties, which provide insights into the range of influence that can be attributed to the LJ term in the QM/MM coupling. The effect of adding additional water in an MM fashion on the geometry optimized nanoparticle structure is small, but more evident effects are seen in its electronic properties. We also show that there is good transferability of existing QM/MM LJ parameters for organic molecules–water interactions to our QM/MM implementation, even though these parameters were obtained with a different QM code and QM/MM implementation, but with the same functional.
关键词： water,geometry optimization,nanoparticles,QM/MM,molecular dynamics,force field parameters,titanium dioxide,multiscale
更新于2025-09-04 15:30:14
-
Perfluorocarbon‐Based <sup>19</sup> F?MRI Nanoprobes for In?Vivo Multicolor Imaging
摘要： In vivo multicolor imaging is important for monitoring multiple biomolecular or cellular processes in biology. 19F magnetic resonance imaging (MRI) is an emerging in vivo imaging technique because it can non-invasively visualize 19F nuclei without endogenous background signals. Therefore, 19F MRI probes capable of multicolor imaging are in high demand. Herein, we report five types of perfluorocarbon-encapsulated silica nanoparticles that show 19F NMR peaks with different chemical shifts. Three of the nanoprobes, which show spectrally distinct 19F NMR peaks with sufficient sensitivity, were selected for in vivo multicolor 19F MRI. The nanoprobes exhibited 19F MRI signals with three colors in a living mouse. Our in vivo multicolor system could be utilized for evaluating the effect of surface functional groups on the hepatic uptake in a mouse. This novel multicolor imaging technology will be a practical tool for elucidating in vivo biomolecular networks by 19F MRI.
关键词： multicolor imaging,fluorine,magnetic resonance imaging,nanoparticles,imaging agents
更新于2025-09-04 15:30:14
-
Gadolinium Doping Enhances the Photoacoustic Signal of Synthetic Melanin Nanoparticles: A Dual Modality Contrast Agent for Stem Cell Imaging.
摘要： In this paper we show that gadolinium-loaded synthetic melanin nanoparticles (Gd(III)-SMNPs) exhibit up to a 40-fold enhanced photoacoustic signal intensity relative to synthetic melanin alone and higher than other metal-chelated SMNPs. This property makes these materials useful as dual labelling agents because Gd(III)-SMNPs also behave as magnetic resonance imaging (MRI) contrast agents. As a proof-of-concept, we used these nanoparticles to label human mesenchymal stem cells (hMSCs). Cellular uptake was confirmed with bright field optical and transmission electron microscopy. The Gd(III)-SMNP labeled stem cells continued to express the stem cell surface markers CD73, CD90, and CD105 and proliferate. The labeled stem cells were subsequently injected intramyocardially in mice, and the tissue was observed by photoacoustic and MR imaging. We found the photoacoustic signal increased as cell number increased (R2 = 0.96) indicating that such an approach could be employed to discriminate between stem cells populations with a limit of detection of 2.3 x 104 cells in in vitro tests. This multimodal photoacoustic/MRI approach combines the excellent temporal resolution of photoacoustics with the anatomic resolution of MRI.
关键词： Photoacoustic Signal,Stem Cell Imaging,Gadolinium,Dual Modality Contrast Agent,Synthetic Melanin Nanoparticles
更新于2025-09-04 15:30:14
-
Physicochemical and Ion-Sensing Properties of Benzofurazan-Appended Calix[4]arene in Solution and on Gold Nanoparticles: Spectroscopy, Microscopy, and DFT Computations in Support of the Species of Recognition
摘要： A calix[4]arene conjugate (L) functionalized at the lower rim with a benzofurazan fluorophore (NBD) and at the upper rim with a thioether moiety has been synthesized and characterized by 1H NMR, 13C NMR, and mass spectrometry techniques. Both the absorption and emission spectral data for L in different solvents exhibited progressive changes with an increase in polarity. Ion recognition studies were performed by absorption and fluorescence spectroscopy using 10 different metal ions. Among these, Hg2+ exhibited greater changes in these spectra, whereas Cu2+ showed only significant changes and all other ions showed no change in the spectral features. Although the Hg2+ has dominant influence on the spectral features and provides a detection limit of 56.0 ± 0.6 ppb, the selectivity was hampered because of the presence of the derivatizations present on both the rims of L for ion interaction in solution. Therefore, L was immobilized onto gold nanoparticles (AuNPL) so that the upper rim derivatizations anchor onto the gold surface through Au?S interactions, and this leaves out only the lower rim NBD derivatization for interaction with ions selectively. The AuNPL’s were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses. The surface characteristics were analyzed by contact angle measurements. The AuNPL’s exhibit greater selectivity and enhanced sensitivity for Hg2+ ions with a lowest detection limit of 48.0 ± 0.8 ppb. The immobilization of L onto AuNPs was reflected in the corresponding fluorescence lifetime values, and the addition of Hg2+ to either L or AuNPL showed fluorescence quenching. The reversible recognition of Hg2+ by L was demonstrated by titrating L or AuNPL with Hg2+ followed by tetra-butyl ammonium iodide for several cycles. The structural features of Hg2+-bound species were demonstrated by density functional theory computations and were supported by the XPS data. The Hg2+ induces aggregated fibrillar morphology into supramolecular L, as demonstrated by microscopy when Hg2+ was added either to L or to AuNPL, supporting aggregation-caused quenching.
关键词： calix[4]arene,benzofurazan,Hg2+ detection,DFT computations,fluorescence quenching,gold nanoparticles
更新于2025-09-04 15:30:14
-
Fe3O4/SiO2 Core Shell Nanostructures: Preparation and Characterization
摘要： Silica coated iron oxide nanoparticles with controlled silica shell thickness were prepared by a modified St?ber method. Modification of the St?ber method consisted of changing the synthesis conditions to control the thickness of the SiO2 shell. The core-shell nanoparticles were characterized by means of X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy and vibrational sample magnetometry. It was found that the shell formed after 8 hours of stirring. An increase of the tetraethoxysilane-magnetite mass ratio from 12.5 to 25.1 led to an increase of the shell thickness, whereas further increase in the tetraethoxysilane-magnetite mass ratio (from 25.1 to 37.6) led to decrease shell thickness. The core size has only insignificant influence on the shell thickness. Magnetic properties of composite particles correlate well with properties of pure magnetite nanoparticles considering dilution of magnetic particles by silica. Obtained results can be used for fabrication of silica shell with controlled thickness on the surface of different sized magnetite nanoparticles.
关键词： FTIR,iron oxide,surface functionalization,silica coated,nanoparticles
更新于2025-09-04 15:30:14
-
Preparation and Use of Chemically Modified Noble Metal Nanoparticles
摘要： Papers dealing with chemical modi? cation of the surface of noble metal nanoparticles and their use in analytical and bioanalytical chemistry, pharmacology, etc., are analyzed. Grafting of a layer of preset chemical composition on the nanoparticle surface allows preparation of functional materials combining the properties of the metal core (surface plasmon resonance, enhancement of ? uorescence and nonelastic scattering) and shell (selective interaction with components of the surrounding medium). Combination of these properties opens wide prospects for using the modi? ed nanoparticles in various branches of science and engineering, primary in chemical and biochemical analysis, and also in pharmacology.
关键词： functional materials,biochemical analysis,noble metal nanoparticles,chemical analysis,chemical modi? cation of the surface
更新于2025-09-04 15:30:14
-
Biosynthesis of Silver Nanoparticles Using <i>Selaginella bryopteris</i> Plant Extracts and Studies of Their Antimicrobial and Photocatalytic Activities
摘要： The present study focuses on the green synthesis of silver nanoparticles (AgNPs) using aqueous extract of S. bryopteris which is a lithophyte with remarkable resurrection capabilities. These biosynthesized NPs were characterized with the help of UV-vis spectrophotometer, X-ray diffraction (XRD), FT-IR and Transmission electron microscopy (TEM). Formation of AgNPs was confirmed by UV-Visible spectrophotometer analysis which showed surface plasmon resonance (SPR) at around 420 nm. The TEM images showed the nanoparticles to be polydispersed, nearly spherical in shape and have sizes in range 4–30 nm. The synthesized AgNPs possessed high antibacterial activity as well as photocatalytic dye degradation properties under solar light irradiation in the absence of chemical reducing reagents. Stability of bio-reduced silver nanoparticles was analyzed using UV-vis absorption spectra, and their antimicrobial activity was screened against various gram-positive bacteria.
关键词： Characterization,Photodegradation,Antimicrobial Activity,Biosynthesis,S. bryopteris Extract,Silver Nanoparticles
更新于2025-09-04 15:30:14
-
Optical Simulations of Self-assembly Relevant Gold Aggregates: A Comparative Study
摘要： In this study, visible light extinction spectra of different gold nanoparticle assemblies were simulated using boundary element method (BEM) in order to investigate the optical properties of structures which determine the experimentally measured spectra during the self-assembly of the particles. Numerous different optically dominant particle arrangements can evolve depending on the underlying physicochemical mechanism of the clustering process itself: one-dimensional chains, two-dimensional arrays or three-dimensional clusters can be formed in the solutions or at interfaces. Experimentally the aggregation or clustering of gold nanoparticles can be conveniently followed by spectroscopic techniques due to the plasmon coupling related profound effect of particle aggregation on the visible extinction spectrum. However, the measured spectra usually contain the optical response of various aggregate structures. Additionally, small changes of the interparticle distance can have a significant impact on the frequency of the coupled mode. In order to assess the contribution of the different structures to the experimentally measurable extinction spectra during particle clustering, different model structures (chains, array and 3D-cluster) have been simulated, where the distance between the particles was varied as well.
关键词： 3D cluster,boundary element method,2D heptamer,self-assembly,optical simulations,nanoparticle chains,gold nanoparticles
更新于2025-09-04 15:30:14
-
Recent Progress in Surface Plasmon Resonance Biosensors (2016 to Mid-2018)
摘要： More than 50 papers on surface plasmon resonance biosensors, published between 2016 and mid-2018, are reviewed. Papers concerning the determination of large particles such as vesicles, exosomes, cancer cells, living cells, stem cells, and microRNA are excluded, as these are covered by a very recent review. The reviewed papers are categorized into five groups, depending on the degree of maturity of the reported solution; ranging from simple marker detection to clinical application of a previously developed biosensor. Instrumental solutions and details of biosensor construction are analyzed, including the chips, receptors, and linkers used, as well as calibration strategies. Biosensors with a sandwich structure containing different nanoparticles are considered separately, as are SPR (Surface Plasmon Resonance) applications for investigating the interactions of biomolecules. An analysis is also made of the markers determined using the biosensors. In conclusion, there is shown to be a growing number of SPR applications in the solution of real clinical problems.
关键词： antibodies,cancer markers,surface plasmon resonance,receptor immobilization,biosensors,nanoparticles
更新于2025-09-04 15:30:14
-
Phyto-Mediated Photo Catalysed Green Synthesis of Silver Nanoparticles Using Durio Zibethinus Seed Extract: Antimicrobial and Cytotoxic Activity and Photocatalytic Applications
摘要： In the present study, we have developed a green approach for the synthesis of silver nanoparticles (DSAgNPs) using aqueous extract of Durio zibethinus seed and determined its antibacterial, photocatalytic and cytotoxic effects. Surface plasmon resonance confirmed the formation of DSAgNPs with a maximum absorbance (λmax) of 420 nm. SEM and TEM images revealed DSAgNPs were spherical and rod shaped, with a size range of 20 nm and 75 nm. The zeta potential was found to be ?15.41 mV. XRD and EDX analyses confirmed the nature and presence of Ag and AgCl. DSAgNPs showed considerable antibacterial activity, exhibited better cytotoxicity against brine shrimp, and shown better photocatalytic activity against methylene blue. Based on the present research work, it can be concluded that DSAgNPs could be used in the field of water treatment, pharmaceuticals, biomedicine, biosensor and nanotechnology in near future.
关键词： antibacterial,silver,Durio zibethinus seed,green synthesis,cytotoxicity,nanoparticles
更新于2025-09-04 15:30:14