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High-Performance Chromatographic Characterization of Surface Chemical Heterogeneities of Fluorescent Organic–Inorganic Hybrid Core–Shell Silica Nanoparticles
摘要： In contrast to small-molar-mass compounds, detailed structural investigations of inorganic core–organic ligand shell hybrid nanoparticles remain challenging. The assessment of batch-reaction-induced heterogeneities of surface chemical properties and their correlation with particle size has been a particularly long-standing issue. Applying a combination of high-performance liquid chromatography (HPLC) and gel permeation chromatography (GPC) to ultra-small (<10 nm diameter) poly(ethylene glycol)-coated (PEGylated) fluorescent core–shell silica nanoparticles, we elucidate here previously unknown surface heterogeneities resulting from varying dye conjugation to nanoparticle silica cores and surfaces. Heterogeneities are predominantly governed by dye charge, as corroborated by molecular dynamics simulations. We demonstrate that this insight enables the development of synthesis protocols to achieve PEGylated and targeting ligand-functionalized PEGylated silica nanoparticles with dramatically improved surface chemical homogeneity, as evidenced by single-peak HPLC chromatograms. Because surface chemical properties are key to all nanoparticle interactions, we expect these methods and fundamental insights to become relevant to a number of systems for applications, including bioimaging and nanomedicine.
关键词： surface chemistry heterogeneity,high-performance liquid chromatography,nanoparticle characterization,nanoparticle surface functionalization,fluorescence correlation spectroscopy,molecular dynamics,nanoparticle heterogeneity
更新于2025-09-23 15:23:52
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Decoupling Effects of Surface Recombination and Barrier Height on p-Si(111) Photovoltage in Semiconductor|Liquid Junctions via Molecular Dipoles and Metal Oxides
摘要： This work provides insight into carrier dynamics in a model photoelectrochemical system comprised of a semiconductor, metal oxide, and metal. To isolate carrier dynamics from catalysis, a common catalytic metal (Pt) is used in concert with an outer-sphere redox couple. Silicon (111) substrates were surface-functionalized with electronegative aryl moieties (p-nitrophenyl and m-dinitrophenyl). A mixed monolayer using p-nitrophenyl/methyl exhibited high surface quality as determined by X-ray photoelectron spectroscopy (low surface SiOx content) and low surface recombination velocity. This substrate also exhibited the expected positive surface dipole, as evidenced by rectifying J?V behavior on p-type substrates, and by positive photovoltage measured by surface photovoltage spectroscopy. Its close molecular relative m-dinitrophenyl exhibited poor electronic surface quality as indicated by high SiOx coverage and high surface recombination velocities (S > 3000 cm s?1). Photoelectrochemical J?V measurements of p-type Si-functionalized surfaces in contact with a high concentration (50 mM) of methyl viologen (MV2+) in aqueous media revealed VOC values that are correlated with the measured barrier heights. In contrast, low-concentration (1.5 mM) MV2+ experiments revealed significant contributions from surface recombination. Next, the electronic and (photo)electrochemical properties were studied as a function of ALD metal oxide deposition (TiO2, Al2O3) and Pt deposition. For the m-dinitrophenyl substrate, ALD deposition of both TiO2 and Al2O3 (150 °C, amorphous) decreased the surface recombination velocity. Surprisingly, this TiO2 deposition resulted in negative shifts in VOC for all surfaces (possibly ALD-TiO2 defect band effects). However, Pt deposition recovered the efficiencies beyond those lost in TiO2 deposition, affording the most positive VOC values for each substrate. Overall, this work demonstrates that (1) when carrier collection is kinetically fast, p-Si(111)?R devices are limited by thermal emission of carriers over the barrier, rather than by surface recombination. And (2) although TiO2 |Pt improves the PEC performance of all substrates, the beneficial effects of the underlying (positive) surface dipole are still realized. Lastly (3) Pt deposition is demonstrated to provide beneficial charge separation effects beyond enhancing catalytic rates.
关键词： solar fuels,interfacial dipole,atomic layer deposition (ALD),surface functionalization,band-edge modulation,photoelectrochemistry
更新于2025-09-23 15:22:29
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Growth mechanisms of F4-TCNQ on inorganic substrates and nanostructures
摘要： The organic semiconductor tetrafluorotetracyanoquinodimethane (F4-TCNQ) is a promising candidate for the doping of organic semiconductors, two-dimensional materials and inorganic compounds, such as ZnO, and also to enhance the charge carrier injection at contacts in organic electronics. In order to evaluate its applicability as a functionalization material or as an electrically active part in devices, we present a systematic study on the growth mode of F4-TCNQ beyond the first few monolayers on different inorganic substrates that cover a broad variety regarding their physical, chemical and morphological surface properties. The materials used are silicon, silicon carbide, graphene on silicon, sapphire, nanocrystalline diamond, as well as gallium nitride (GaN) layers and nanowire arrays. While the surface termination influences the shape and morphology of the islands of F4-TCNQ which form on all substrates investigated, no significant dependence of the growth mode on the substrate doping type and concentration is observed. GaN nanowires are found to act as nucleation sites for F4-TCNQ islands and to be covered by few monolayers of F4-TCNQ forming a closed coaxial shell. In conclusion, F4-TCNQ is identified to nucleate via Stranski-Krastanov growth consisting of monolayers and islands of different size and shape. The findings in this work provide basic growth information for the implementation of F4-TCNQ as functionalization material for nanowire-based applications.
关键词： GaN nanowires,surface functionalization,growth mode,organic semiconductors,organic electronics,surface doping,F4-TCNQ
更新于2025-09-23 15:21:01
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Surface functionalization by laser-induced periodic surface structures
摘要： In recent years, the improved understanding of the formation of laser-induced periodic surface structures (LIPSS) has led to an emerging variety of applications that modify the optical, mechanical, and chemical properties of many materials. Such structures strongly depend on the laser beam polarization and are formed usually after irradiation with ultrashort linearly polarized laser pulses. The most accepted explanation for the origin of the structures is based on the interference of the incident laser radiation with electromagnetic surface waves that propagate or scatter at the surface of the irradiated materials. This leads to an intensity modulation that is finally responsible for the selective ablation in the form of parallel structures with periods ranging from hundreds of nanometers up to some micrometers. The versatility when forming such structures is based on the high reproducibility with different wavelengths, pulse durations and repetition rate laser sources, customized micro- and nanometric spatial resolutions, and compatibility with industrially relevant processing speeds when combined with fast scanning devices. In this contribution, we review the latest applications in the rapidly emerging field of surface functionalization through LIPSS, including biomimetic functionalities on fluid transport, control of the wetting properties, specific optical responses in technical materials, improvement of tribological performance on metallic surfaces, and bacterial and cell growth for medical devices, among many others.
关键词： applications,laser processing,surface functionalization,laser-induced periodic surface structures (LIPSS)
更新于2025-09-23 15:21:01
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Synthesis, characterization, and cytotoxicity assessment of N-acetyl-L-cysteine capped ZnO nanoparticles as camptothecin delivery system
摘要： The chemical stability, good biocompatibility and high drug loading capacity of zinc oxide nanoparticles (ZnO NPs) and their biomedical potentials make them a promising candidate for drug delivery. The aim of this study was to develop and assess a simple procedure for surface functionalization of ZnO NPs by N-acetyl-L-cysteine (NAC) for anticancer camptothecin (CPT) delivery. NAC capped ZnO NPs were successfully made using ZnCl2 and NaOH in the presence of NAC. CPT was covalently conjugated to the surface of as-synthesized ZnO-NAC NPs. To characterize the synthesized conjugate product (ZnO-NAC-CPT NPs), X-ray diffraction, Fourier Transform Infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and dynamic light scattering method were used. Our results indicated that the ZnO-NAC-CPT NPs exhibit near-spherical morphology and uniform dispersion with an average diameter of ~70 nm. The hemolysis assay showed that ZnO-NAC-CPT NPs has almost no hemolytic activity. In addition, MTT cytotoxicity assessment on A549 lung cancer cells revealed a drop of IC50 values from 1.17 μg/mL (free CPT) to 0.66 μg/mL (ZnO-NAC-CPT NPs). This result showed an augmented cancer-inhibitory effect of nanoconjugate complex. In conclusion, the novel ZnO-NAC-CPT NPs could be considered for new therapeutic endeavors.
关键词： surface functionalization,N-acetyl-L-cysteine,camptothecin,ZnO nanoparticles,cytotoxicity
更新于2025-09-23 15:21:01
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Plasmonic biosensors fabricated by galvanic displacement reactions for monitoring biomolecular interactions in real time
摘要： Optical sensors are prepared by reduction of gold ions using freshly etched hydride-terminated porous silicon, and their ability to specifically detect binding between protein A/rabbit IgG and asialofetuin/Erythrina cristagalli lectin is studied. The fabrication process is simple, fast, and reproducible, and does not require complicated lab equipment. The resulting nanostructured gold layer on silicon shows an optical response in the visible range based on the excitation of localized surface plasmon resonance. Variations in the refractive index of the surrounding medium result in a color change of the sensor which can be observed by the naked eye. By monitoring the spectral position of the localized surface plasmon resonance using reflectance spectroscopy, a bulk sensitivity of 296 nm ± 3 nm/RIU is determined. Furthermore, selectivity to target analytes is conferred to the sensor through functionalization of its surface with appropriate capture probes. For this purpose, biomolecules are deposited either by physical adsorption or by covalent coupling. Both strategies are successfully tested, i.e., the optical response of the sensor is dependent on the concentration of respective target analyte in the solution facilitating the determination of equilibrium dissociation constants for protein A/rabbit IgG as well as asialofetuin/Erythrina cristagalli lectin which are in accordance with reported values in literature. These results demonstrate the potential of the developed optical sensor for cost-efficient biosensor applications.
关键词： Surface functionalization,Optical sensor,Lectin,Localized surface plasmon resonance,Biomolecular interactions,Gold nanostructure
更新于2025-09-23 15:19:57
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Microcavity Nonlinear Optics with an Organically Functionalized Surface
摘要： We report enhanced optical nonlinear effects at the surface of an ultrahigh-Q silica microcavity functionalized by a thin layer of organic molecules. The maximal conversion efficiency of third harmonic generation reaches ～1680%=W2 and an absolute efficiency of 0.0144% at pump power of ～2.90 mW, which is approximately 4 orders of magnitude higher than that in a reported silica microcavity. Further analysis clarifies the elusive dependence of the third harmonic signal on the pump power in previous literature. Molecule-functionalized microcavities may find promising applications in high-efficiency broadband optical frequency conversion and offer potential in sensitive surface analysis.
关键词： Nonlinear Optics,Microcavity,Third Harmonic Generation,Surface Functionalization,Organic Molecules
更新于2025-09-23 15:19:57
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Compact, a??Clickablea?? Quantum Dots Photoligated with Multifunctional Zwitterionic Polymers for Immunofluorescence and In-Vivo Imaging
摘要： We detail the preparation of highly fluorescent quantum dots (QDs), surface-engineered with multifunctional polymer ligands that are compact, readily compatible with strain-promoted click conjugation, and the use of these nanocrystals in immunofluorescence and in-vivo imaging. The ligand design combines the benefits of mixed coordination (i.e., thiol and imidazole) with molecular-scale zwitterion motifs, yielding sterically-stabilized and compact QDs that present a controllable number of azide groups, for easy conjugation to biomolecules via the efficient and selective click chemistry. The polymer coating was characterized using NMR spectroscopy to extract estimates of the diffusion coefficient, hydrodynamic size and ligand density. The azide-functionalized QDs were conjugated to anti-tropomyosin receptor kinase B antibody (α-TrkB), or to the brain-derived neurotrophic factor (BDNF). These conjugates were highly effective for labeling the tropomyosin receptor kinase B (TrkB) in pyramidal neurons within cortical tissue and for monitoring the BDNF induced activation of TrkB signaling in live neuronal cells. Finally, the polymer-coated QDs were applied for in vivo imaging of Drosophila Melanogaster embryo, where the QDs remain highly fluorescent and colloidally stable, with no measurable cytotoxicity. These materials would be of great use in various imaging applications, where small size, ease of conjugation and great colloidal stability for in vivo studies are needed.
关键词： click chemistry,BDNF/TrkB,polymers,surface functionalization,embryo imaging,quantum dots
更新于2025-09-23 15:19:57
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Application of carbon dots in dye‐sensitized solar cells: A review
摘要： Carbon dots (CDs) are a kind of zero-dimensional carbon-based nanoparticles with superb light-trapping ability, high optical absorption ability, and superior intrinsic catalytic activity. Due to these advantageous properties, they have received enthusiastic attention from researchers in the field of optical devices. The application of carbon dots in dye-sensitized solar cells has increased with steady steps recently, especially as a substitute for precious Ru-sensitizers and Pt counter electrodes. In this review, we classified the application of carbon dots in dye-sensitized solar cells in recent years and explained the mechanisms of improving the performance of carbon dots. The significant impact of surface functionalization of CDs on the performance of dye-sensitized solar cells was discussed. Lastly, some challenges and application prospects of carbon dots in the dye-sensitized solar cell were proposed, which is meaningful for the further exploration and application of carbon dots as a new energy material.
关键词： sensitizer,counter electrode,carbon dots,surface functionalization,dye-sensitized solar cells
更新于2025-09-19 17:13:59
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Ultrashort Pulsed Laser Surface Patterning of Titanium to Improve Osseointegration of Dental Implants
摘要： Ultrashort pulsed direct laser interference patterning (DLIP) is used to generate hierarchical line-like patterns on titanium surfaces to control cell adhesion and spreading on dental implants, thereby improving osseointegration. The DLIP structures have spatial periods of 3, 5, 10, and 17 μm. They are produced using a laser source with a pulse duration of 10 ps and cumulated energy densities between 0.1 and 78.9 J cm?2. Laser-induced periodic surface structures (LIPSS) and submicron features are obtained on the treated samples. The DLIP treatment leads to the development of a thick titanium oxide layer, which is imaged and quantified using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Several days (30–56) after the laser treatment, specimens with larger spatial periods are hydrophilic, whereas samples with spatial periods of 3 μm are hydrophobic. Seeded human osteoblasts on the laser-structured samples show 2.5 times higher cell numbers after 7 days in vitro culture compared with osteoblasts on a grit-blasted and etched reference sample. Finally, cell adhesion to a structured 3D dental implant is demonstrated.
关键词： dental implants,surface functionalization,direct laser interference patterning,osseointegration,titanium
更新于2025-09-19 17:13:59