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Gold-tagged Polymeric Nanoparticles with Spatially Controlled Composition for Enhanced Detectability in Biological Environments
摘要： Organic nanoparticles offer the advantage of high biocompatibility for biomedical applications but suffer frequently from poor visibility in biological environments. While fluorescent-labeling is convenient and allows for fast and extensive histological analysis, fluorescence imaging and quantitative analysis are limited by low resolution and significantly hindered by tissue auto-fluorescence. Labeling of polymeric nanoparticles with an additional gold tag would allow for high resolution imaging via transmission electron microscopy (TEM) and for quantification of particles by inductively coupled plasma optical emission spectrometry (ICP-OES). However, spatially uncontrolled gold-tagging can cause significant fluorescence quenching. To overcome this restraint, 2.2 nm gold nanoparticles were introduced at the interface between the hydrophobic fluorophore-loaded core and the hydrophilic shell of polymeric nanoparticles. Due to the small size of gold labels and the spatially controlled stratified composition of hybrid nanoparticles, fluorescence quenching by gold tags was minimized to 15.1%, allowing for concomitant detection of both labels via optical microscopy after enhancement of the gold tags. Multilayered hybrid nanoparticles exhibited outstanding detectability by transmission electron microscopy, even without additional sample staining. Furthermore, they were capable of producing remarkable image contrast inside cells after gold or silver enhancement. The interfacial gold layer increased the hydrodynamic particle size only marginally from 71.8 to 89.5 nm and had no negative impact on biocompatibility in vitro. The gold content (0.75% m/m) is sufficiently high for future quantification in tissues after systemic administration. With their clean-cut structure and superior detectability, multilayered hybrid nanoparticles constitute an outstanding blueprint and a precious tool for the development of nanomedicines.
关键词： gold,polymeric nanoparticles,hybrid,TEM,PLGA,contrast agent
更新于2025-11-21 11:24:58
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Synthesis of Nanocrystalline SnxCd1?xS Thin Films Capped with Thioglycerol and Methanol (TGM) and Study of Optical and Structural Properties
摘要： Nanostructured CdS (nCdS) and ternary SnxCd1?xS thin films capped with thioglycerol and methanol in 1:1 ratio in aqueous medium were prepared using hydrated stannous chloride (SnCl2·2H2O), anhydrous cadmium acetate (CH3COO)Cd·2H2O and thiourea (CS(NH2)2) as sources of Sn, Cd and S ions, respectively. Thickness of the film drastically decreases for low concentrations (0–2%) of Sn doping, then increases for (2–3%) and 5% Sn doping. Effects of Sn concentration variation on the optical properties, photoluminescence and structural properties of the nanoparticles were studied. The optical transmittance measurement using ultraviolet–visible–near infrared spectroscopy showed more than 80% transparency in the wavelength range 450–800 nm for 3% and 5% Sn doping. The direct optical band gap value of nanoCdS thin films was obtained as 2.91 eV, which decreased with Sn doping for its varying concentrations. Photoconductivity gain was negligible. A decrease in intensity of lower wavelength emission at 430 nm in nCdS was observed to have (2–5)% Sn content. X-ray diffraction patterns and selected area electron diffraction patterns confirmed formation of the nanocrystalline hexagonal CdSnS phase. Scanning electron microscope and transmission electron microscope measurements of the CdSnS thin films show that the particle size lies well under 20 nm.
关键词： SEM,TEM,photoluminescence,Optical study,XRD
更新于2025-11-21 11:18:25
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Microstructure and properties of laser interference crystallized amorphous FeSiB ribbon
摘要： The influence of Q-switched pulsed Nd:YAG laser interference heating, using 120 mJ of pulse energy and a variable number of consecutive pulses, on the microstructure and magnetic properties of amorphous Fe80Si11B9 alloy was examined. Microstructural analysis, using light, scanning and transmission electron microscopy, was complemented by results of M?ssbauer spectroscopy and measurement of magnetic properties (vibrating sample magnetometer). Periodically distributed crystallized micro-areas, *10 lm in diameter, in an amorphous matrix were produced by the treatments. Magnetization measurements showed that the as-cast ribbon and laser light irradiated samples are magnetically soft materials. The results lead to the conclusion that the dots corresponding to the laser modified regions exhibit a perpendicular magnetic anisotropy.
关键词： Laser interference heating,SEM,TEM,FeSiB amorphous alloy,Magnetic properties
更新于2025-11-14 17:04:02
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Synthesis, characterization and dye sensitized solar cell application of Zinc oxide based coaxial core-shell hetrostructure.
摘要： In the present work, the ZnO/CdS coaxial core shell hetrostructure has been synthesized on indium doped tin oxide glass substrate using chemical solution methods and further it is used as photoanode in the DSSC application. Four samples with different concentration of sulphur source were prepared. An approximate crystallite size of 22 nm for ZnO and 18 nm for CdS has been obtained as analyzed from X-ray diffraction data. FESEM and HRTEM images confirm the formation of CdS shell on ZnO nanorods with a width below 100 nanometer. UV-visible spectroscopy and photoluminescence spectroscopy were used to examine the optical response revealing the fact that band gap reduction and a small red shift takes place for core shell structure as compared to bare ZnO nanorods array. The J-V characterization was performed to study the photovoltaic response. An improved efficiency was observed for core shell ZnO/CdS hetrostructure (3.66%) as compared to bare ZnO nanorods based DSSCs (0.70%). This improvement is due to increased current density caused by reduced recombination of photogenerated electron hole pairs. This reduced recombination is achieved by two factors, one is formation of type two core shell hetrostructure and second is increasing sulphur concentration in shell structure.
关键词： DSSC,Hetrostructure,FESEM,HR-TEM,coaxial core-shell
更新于2025-11-14 17:04:02
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Direct Observation of Structural Evolution of Metal Chalcogenide in Electrocatalytic Water Oxidation
摘要： As one of the most remarkable oxygen evolution reaction (OER) electrocatalysts, metal chalcogenides have been intensively reported due to their high OER activities during the past few decades. It has been reported that electron-chemical conversion of metal chalcogenides into oxides/hydroxides would take place after OER. However, the transition mechanism of such unstable structures, as well as the real active sites and catalytic activity during OER for these electrocatalysts, has not been understood yet, which urgently needs a direct observation for the electrocatalytic water oxidation process, especially at nano or even angstrom scale. In this research, by employing advanced Cs-corrected transmission electron microscopy (TEM), a step by step oxidational evolution of amorphous electrocatalyst CoSx into crystallized CoOOH in OER has been in situ captured: irreversible conversion of CoSx to crystallized CoOOH is initiated on the surface of electrocatalysts with a morphology change via Co(OH)2 intermediate during OER measurement, where CoOOH is confirmed as the real active species. Besides, this transition process has also been confirmed by multiple applications of X-ray photoelectron spectroscopy (XPS), in situ Fourier-transform infrared spectroscopy (FTIR) and other ex situ technologies. Moreover, based on this discovery, a high-efficiency electrocatalyst of a nitrogen-doped graphene foam (NGF) coated by CoSx has been explored through a thorough structure transformation of CoOOH. We believe this in situ and in-depth observation of structural evolution in OER measurement can provide insights into the fundamental understanding of the mechanism for OER catalysts, thus enabling the more rational design of low-cost and high-efficient electrocatalysts for water splitting.
关键词： structural evolution,XPS,in situ TEM,water oxidation,cobalt chalcogenide
更新于2025-11-14 15:27:09
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Nano-Heteroepitaxy: An Investigation of SiGe Nano-Pillars Coalescence
摘要： In this paper, SiGe nano-pillars coalescence was investigated using industrial Reduced Pressure-Chemical Vapour Deposition integration scheme based on diblock copolymer patterning provided nanometer size templates for the selective epitaxy of SiGe 25% nano-pillars. In order to study merging, thicknesses ranging from 20 to 35 nm were grown and samples characterized by AFM, XRD, SSRM and TEM. The evolution in terms of grains shape, size and number was examined, with individual pillars merging into larger grains above 30 nm thickness. High degrees of macroscopic strain relaxation were obtained at the different stages of nano-pillars merging. Defects such as stacking faults and twins were identified as occurring at the early stages of nano-pillar coalescence.
关键词： SSRM,TEM,coalescence,AFM,SiGe nano-pillars,Reduced Pressure-Chemical Vapour Deposition,XRD
更新于2025-11-14 14:32:36
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Single process CVD growth of hBN/Graphene heterostructures on copper thin films
摘要： In this study, we have successfully grown hBN/graphene heterostructures on copper thin films using chemical vapor deposition in a single process. The first and most surprising result is that graphene grows underneath hBN and adjacent to the Cu film even though it is deposited second. This was determined from cross-sectional TEM analysis and XPS depth profiling, which chemically identified the relative positions of hBN and graphene. The effect of various growth conditions on graphene/hBN heterostructures was also studied. It was found that a pressure of 200 torr and a hydrogen flow rate of 200 sccm (;1 H2/N2) yielded the highest quality of graphene, with full surface coverage occurring after a growth time of 120 min. The resulting graphene films were found to be approximately 6–8 layers thick. The grain size of the nanocrystalline graphene was found to be 15–50 nm varying based on growth conditions.
关键词： XPS depth profiling,copper thin films,TEM analysis,hBN/graphene heterostructures,chemical vapor deposition
更新于2025-11-14 14:32:36
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Nanofluidic and monolithic environmental cells for cryogenic microscopy
摘要： We present a device capable of combining nanofluidics and cryogenic transmission electron microscopy (cryo-TEM) to allow inspection of water-soluble samples under near-native conditions. The devices can be produced in a multitude of designs, but as a general rule, they consist of channels or chambers enclosed between two electron-transparent silicon nitride windows. With the appropriate design, those devices can allow screening of multiple samples in parallel and remove the interaction between the sample and the environment (no air–water interface). We demonstrate channel sizes from 80 to 500 nm in height and widths from 100 to 2000 μm. The presented fabrication flow allows producing hollow devices on a single wafer eliminating the need of aligning or bonding two half-cavities from separate wafers, which provides additional resistance to thermal stress. Taking advantage of a single-step through-membrane exposure with a 100 keV electron beam, we introduced arrays of thin (10–15 nm) electron-transparent silicon nitride membrane windows aligned between top and bottom (200–250 nm) carrier membranes. Importantly, the final devices are compatible with standard TEM holders. Furthermore, they are compatible with rapid freezing of samples, which is crucial for the formation of vitreous water, hence avoiding the formation of crystalline ice, that is detrimental for TEM imaging. To demonstrate the potential of this technology, we tested those devices in imaging experiments verifying their applicability for cryo-TEM applications and proved that vitreous water could be prepared through conventional plunge freezing of the chips.
关键词： nanofabrication,TEM,environmental chamber,microfluidic cell,electron beam lithography,cryo-TEM
更新于2025-09-23 15:23:52
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Development of novel correlative light and electron microscopy linkage system using silicon nitride film
摘要： In this study, we investigated the optical properties of a silicon nitride (SiN) film. The thin SiN film (30 nm thick) exhibited good light transmittance and little autofluorescence and could be used as a microscope slide for optical microscopy (OM). In addition, we developed a novel correlative light and electron microscopy (CLEM) that combines OM with transmission electron microscopy (TEM) using an SiN thin film. In this system, CLEM was performed by replacing a detachable retainer with a holder for TEM and an adaptor for OM. The advantage of this method is that the same specimens can be sequentially observed using suitable OM and TEM.
关键词： TEM holder,correlative microscopy,SiN film,exchangeable retainer,OM–TEM integration
更新于2025-09-23 15:23:52
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Anomalous shape evolution of Ag2O2 nanocrystals modulated by surface adsorbates during electron beam etching
摘要： An understanding of nanocrystal shape evolution is significant for the design, synthesis and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on shape control of nanocrystals.
关键词： surface adsorbates,Ag2O2 nanocrystal,shape evolution,In situ TEM,electron beam etching
更新于2025-09-23 15:23:52