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Quantitative Measure of the Size Dispersity in Ultrasmall Fluorescent Organic-Inorganic Hybrid Core-Shell Silica Nanoparticles by Small-angle X-ray Scattering
摘要： Small-angle X-ray scattering (SAXS) was performed on dispersions of ultrasmall (d < 10 nm) fluorescent organic-inorganic hybrid core-shell silica nanoparticles synthesized in aqueous solutions (C′ dots) by using an oscillating flow cell to overcome beam induced particle degradation. Form factor analysis and fitting was used to determine the size and size dispersity of the internal silica core containing covalently encapsulated fluorophores. The structure of the organic poly(ethylene glycol) (PEG) shell was modelled as a monodisperse corona containing concentrated and semi-dilute regimes of decaying density and as a simple polydisperse shell to determine the bounds of dispersity in the overall hybrid particle. C′ dots containing single growth step silica cores have dispersities of 0.19-0.21; growth of additional silica shells onto the core produces a thin, dense silica layer, and increases the dispersity to 0.22-0.23. Comparison to FCS and DLS measures of size shows good agreement with SAXS measured and modelled sizes and size dispersities. Finally, comparison of a set of same sized and purified particles demonstrates that SAXS is sensitive to the skewness of the gel permeation chromatography elugrams of the original as-made materials. These and other insights provided by quantitative SAXS assessments may become useful for generation of robust nanoparticle design criteria necessary for their successful and safe use, for example in nanomedicine and oncology applications.
关键词： nanomedicine,size dispersity,core-shell nanoparticles,silica nanoparticles,Small-angle X-ray scattering,PEGylation
更新于2025-09-23 15:23:52
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Ultrathin Y <sub/>2</sub> O <sub/>3</sub> :Eu <sup>3+</sup> nanodiscs: spectroscopic investigations and evidence for reduced concentration quenching
摘要： Here, we report the synthesis and spectral properties of ultrathin nanodiscs (NDs) of Y2O3:Eu3+. It was found that the NDs of Y2O3:Eu3+ with a thickness of about 1 nm can be fabricated in a reproducible, facile and self-assembling process, which does not depend on the Eu3+ concentration. The thickness and morphology of these NDs were determined with small angle x-ray scattering and transmission electron microscopy. We found that the crystal field in these nanoparticles deviates from both the cubic and monoclinic characteristics, albeit the shape of the 5D0 → 7FJ (J = 0, 1, 2) transitions shows some similarity with the transitions in the monoclinic material. The Raman spectra of the non-annealed NDs manifest various vibration modes of the oleic acid molecules, which are used to stabilise the NDs. The annealed NDs show two very weak Raman lines, which may be assigned to vibrational modes of Y2O3 NDs. The concentration quenching of the Eu3+ luminescence of the NDs before annealing is largely suppressed and might be explained in terms of a reduction of the phonon density of states.
关键词： nanodiscs,small angle x-ray scattering,europium-doped yttrium oxide,Raman spectroscopy,concentration quenching,transmission electron microscopy,luminescence
更新于2025-09-23 15:21:21
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Binary Superlattices of Infrared Plasmonic and Excitonic Nanocrystals
摘要： Self-assembled superlattices of nanocrystals offer exceptional control over the coupling between nanocrystals, similar to how solid-state crystals tailor the bonding between atoms. By assembling nanocrystals of different properties (e.g., plasmonic, excitonic, dielectric, or magnetic), we can form a wealth of binary superlattice metamaterials with new functionalities. Here, we introduce infrared plasmonic Cu2?xS nanocrystals to the limited library of materials that have been successfully incorporated into binary superlattices. We are the first to create a variety of binary superlattices with large excitonic (PbS) nanocrystals and small plasmonic (Cu2?xS) nanocrystals, both resonant in the infrared. Then, by controlling the surface chemistry of large Cu2?xS nanocrystals, we produced structurally analogous superlattices of large Cu2?xS and small PbS nanocrystals. Transmission electron microscopy (TEM) and grazing-incidence small-angle X-ray scattering (GISAXS) were used to characterize both types of superlattices. Furthermore, our unique surface modification of the large Cu2?xS nanocrystals also prevented them from chemically quenching the photoluminescence of the PbS nanocrystals, which occurred when the PbS nanocrystals were mixed with unmodified Cu2?xS nanocrystals. These synthetic achievements create a set of binary superlattices that can be used to understand how infrared plasmonic and excitonic nanocrystals couple in a variety of symmetries and stoichiometries.
关键词： infrared quantum dots,nanocrystals,self-assembly,supracrystal,metamaterial,binary superlattice,grazing-incidence small-angle X-ray scattering (GISAXS)
更新于2025-09-23 15:21:01
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Micelle-Assisted Formation of Nanoparticle Superlattices and Thermally Reversible Symmetry Transitions
摘要： Nanoparticle superlattices (NPSLs) are of great interests as materials with designed emerging properties depending on the lattice symmetry as well as composition. The symmetry transition of NPSLs depending on environmental conditions can be an excellent ground for making new stimuli-responsive functional materials. Here, we report a spherical micelle-assisted method to form exceptionally ordered NPSLs which are inherently sensitive to environmental conditions. Upon mixing functionalized gold nanoparticles (AuNPs) with a nonionic surfactant spherical micellar solution, NPSLs of different symmetries such as NaZn13, MgZn2, and AlB2-type are formed depending on the size ratio between micelles and functionalized AuNPs, and composition. The NPSLs formed by the spherical micelle-assisted method show thermally reversible order-order (NaZn13–AlB2) and order-disorder (MgZn2–isotropic) symmetry transitions, which are consistent with the Gibbs free energy calculations for binary hard-sphere model. This approach may open up new possibilities for NPSLs as stimuli-responsive functional materials.
关键词： small-angle x-ray scattering,nanoparticle superlattice,spherical micelle,stimuli-responsive symmetry transition
更新于2025-09-19 17:15:36
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Elongated Nanodomains and Molecular Intermixing Induced Doping in Organic Photovoltaic Active Layers with Electric Field Treatment
摘要： The effects of the electric-field-assisted annealing on the bulk heterojunction nano-morphology in the P3HT/PCBM active layer of the organic photovoltaic cells (OPVCs) are presented here. It was widely accepted that the electric-field-assisted annealing will facilitate the P3HT, the polar polymer, to be better crystalline to enhance the charge mobility, hence the improvement of the OPVC performance. The influences on the nano-morphology of the electron donor and accepter domains are not well understood. Here, using the cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S), the electric-field-assisted annealing treatment is found to influence the molecular domains to be elongated along the direction of the external electric field. The elongation of the molecular domains is believed to facilitate the domain percolation, which causes higher charge mobility, hence the higher short-circuit current density (Jsc). On the other hand, it was also observed that the electronic properties of the P3HT-rich and PCBM-rich domains in the electric-field-assisted annealed samples showed smaller energy band gaps and smaller molecular orbital offset between the two domains, which is believed to decrease the open circuit voltage (Voc) and negatively impact the OPVC performance. Based on the X-ray diffraction (XRD) and small angle X-ray scattering (SAXS) results, the altered electronic properties are argued to be due to the molecular intermixing induced doping effects. These results point out competing factors affecting the OPVC performance with the electric-field-assisted annealing treatment.
关键词： Bulk heterojunction,Cross-sectional scanning tunneling microscopy,Organic Solar Cells,X-ray Diffraction,Small Angle X-ray Scattering,Nanomorphology
更新于2025-09-12 10:27:22
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Comparison of UV-Irradiation and Sintering on Mesoporous Sponge-like ZnO Films Prepared from PS-b-P4VP Templated Sol-Gel Synthesis
摘要： Mesoporous ZnO films with large surface-area-to-volume-ratio show great promise in multiple applications, among which solid-state dye-sensitized solar cells (ssDSSCs) have attracted great attention in the field of photovoltaics. An appropriate mesopore size in the nanostructured ZnO films significantly plays an indispensable role in improving the device efficiency resulted from an efficient penetration of dye molecules and solid hole transport material. In the present work, mesoporous sponge-like ZnO films are prepared using sol-gel synthesis templated by a diblock copolymer polystyrene-block-poly(4-vinylpyridine). Two different template removal techniques, UV-irradiation and high temperature sintering, are used to compare their respective impact on the pore sizes of the final ZnO thin films. Both, the surface morphology and the inner morphology show that mesopores obtained via UV-irradiation are smaller as compared to their sintered counterparts. Moreover, increasing the template-to-ZnO precursor ratio is found to further enlarge present mesopores. Accordingly, a strong correlation between the pore sizes of sol-gel synthesized ZnO films and photovoltaic performance of fabricated ssDSSCs is demonstrated. In contrast with the devices fabricated from the UV-irradiated ZnO films, those obtained from sintered samples show more than two times higher efficiency.
关键词： sintering,mesopores,grazing-incidence small-angle X-ray scattering,UV-irradiation,solid-state DSSCs
更新于2025-09-10 09:29:36
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Colloidal Crystals of NaYF <sub/>4</sub> Upconversion Nanocrystals Studied by Small-Angle X-Ray Scattering (SAXS)
摘要： Spherical NaYF4 upconversion nanocrystals with mean radii of about 5 and 11 nm are observed to form colloidal crystals, i.e., 3D assemblies of the particles with long-range order. The colloidal crystals of the larger particles form directly in solution when dispersions of the particles in toluene are stored at room temperature for several weeks. Crystallization of the smaller particles takes place when their dispersions in hexane are slowly dried at elevated temperatures. The formation and the structure of the colloidal crystals are studied by small-angle X-ray scattering (SAXS). SAXS measurements show that the smaller as well as the larger particles assemble into a face-centered cubic lattice with unit cell dimensions of a = 18.7 nm and a = 35.5 nm, respectively. The SAXS data also show that the particles in the colloidal crystals still bear a layer of oleic acid on their surfaces. The thickness of this layer is 1.5–1.8 nm, as determined by comparing the unit cell dimensions of the colloidal crystals with the mean particle sizes. The latter could be very precisely determined from the distinct oscillations observed in the SAXS data of dilute colloidal dispersions of the nanocrystals.
关键词： upconversion,colloidal crystals,nanocrystals,small-angle X-ray scattering
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI, USA (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Fundamental Characterization of Anti-Soiling Coatings for PV Glass: Application of Small-Angle X-ray Scattering
摘要： When dust and other particulates accumulate on the surface of solar modules, the efficiency of these soiled modules is significantly reduced. Soiling is especially problematic in regions with little rain, where water resources for cleaning modules are scarce. To combat this issue, anti-soiling coatings, on the top-surface of solar modules, are beginning to enter the market. However, limited understanding of anti-soiling mechanisms and uncertainty in their durability has limited their deployment. Porous coatings are anticipated to discourage soiling because their rough surfaces reduce the strength and probability of dirt-to-coating bonds. However, the evolution of this morphology through soiling cycles is largely unknown. Here we present the use of small angle X-ray scattering (SAXS) to monitor the morphology of pristine and soiled, industry-sourced coatings. Initial soiling tests are performed using a standardized soil (AZ road dust) in the lab. This work demonstrates the effectiveness of SAXS in monitoring coating morphology despite the presence of soil surface layers. The capability of SAXS studies to be performed under various temperature, humidity, and soiling conditions sets it apart as a strong characterization tool for developing the understanding of functionality and degradation mechanisms of anti-soiling coatings for PV glass.
关键词： soiling,anti-soiling,materials forensics,small-angle X-ray scattering,anti-reflection,PV glass,coatings,self-cleaning
更新于2025-09-09 09:28:46
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Conformational change due to intramolecular hydrophobic interaction leads to large blue-shifted emission from single molecular cage solutions
摘要： We demonstrate a unique negative solvatochromic emission (NSE) process from a conformational change of a coordination cage in response to solvent composition. The cationic cage contains two tetra-(4-pyridylphenyl)ethylene (TPPE) luminogens on two opposite faces, linked by Pt(PEt3)2 and isophthalate. When the solvent changes from acetone/acetonitrile/methanol to water, the emission of single cages gradually shifts to short wavelength (NSE) with a drastic value of B60 nm. Small angle X-ray scattering (SAXS) measurements indicate a molecular conformational change during the process and intramolecular p–p stacking and hydrophobic interaction between the TPPE planes could be the driving forces. As a comparison, a cage with a longer inter-fluorophore distance does not have such strong intramolecular interactions and only shows regular positive solvatochromic emission (PSE) under the same conditions.
关键词： coordination cage,intramolecular hydrophobic interaction,small angle X-ray scattering,TPPE luminogens,negative solvatochromic emission
更新于2025-09-04 15:30:14