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Heterogeneous Growth of Continuous ZIF-8 Films on Low-Temperature Amorphous Silicon
摘要： Thin amorphous silicon films, deposited at low temperature by Inductively Coupled Plasma Chemical Vapor Deposition, have, for the first time, been employed as substrate for ZIF-8 growth. In order to investigate the role of the surface chemistry on the nucleation process, films have also been grown on other silicon-based substrates such as H-terminated Si(100), SiO2 and quartz. Film preparation was carried out at room temperature using a mixed Zn nitrate and imidazole solution in methanol or ethanol. Using methanol, continuous ZIF-8 films were obtained on amorphous Si and H-terminated Si(100), while less homogeneous films were formed on the other surfaces. In ethanol, slower growth rates occurred and thinner films, compared to the ones in methanol, were obtained. These slower rates highlight the different effects of the four surfaces on the growth process. These differences have been related to the silanol density of the surfaces and to the Lewis basic strength which affect imidazole moiety deprotonation. H-terminated Si(100) and amorphous Si turned out to be the most reactive surfaces, whereas on quartz and, especially, on SiO2 reactivity was much lower. Experimental results have been validated by the DFT modelling of the proton exchange, which takes place between the imidazole group and the surface. Finally, the VOCs adsorption capability of ZIF-8 films grown on amorphous silicon has been evaluated through temperature desorption experiments.
关键词： a-Si layer,ZIF-8 coating,growth mechanisms,VOCs adsorption,surface chemistry
更新于2025-11-21 11:03:25
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Post-synthesis phase and shape evolution of CsPbBr3 colloidal nanocrystals: The role of ligands
摘要： The surface chemistry of colloidal cesium lead bromide (CsPbBr3) nanocrystals is decisive in determining the stability and the final morphology of this class of materials, characterized by ionic structure and a high defect tolerance factor. Here, the high sensitivity of purified colloidal nanocubes of CsPbBr3 to diverse environmental condition (solvent dilution, ageing, ligands post synthetic treatment) in ambient atmosphere is investigated by means of a comprehensive morphological (electron microscopy), structural (θ/2θ X-ray diffraction (XRD) and grazing incidence wide angle scattering (GIWAXS)), and spectroscopic chemical (1H nuclear magnetic resonance (NMR), nuclear Overhauser effect spectroscopy (NOESY), absorption and emission spectroscopy) characterization. The aging and solvent dilution contribute to modify the nanocrystal morphology, due to a modification of the ligand dynamic. Moreover, we establish the ability of aliphatic carboxylic acids and alkyl amines ligands to induce, even in a post preparative process at room temperature, structural, morphological and spectroscopic variations. Upon post synthesis alkyl amine addition, in particular of oleyl amine and octyl amine, the highly green emitting CsPbBr3 nanocubes effectively turn into one-dimensional (1D) thin tetragonal nanowires or lead halide deficient rhombohedral zero-dimensional (0D) Cs4PbBr6 structures with a complete loss of fluorescence. The addition of an alkyl carboxylic acid, as oleic and nonanoic acid, produces the transformation of nanocubes into still emitting orthorombic two-dimensional (2D) nanoplates. The acid/base equilibrium between the native and added ligands, the adsorbed/free ligands dynamic in solution and the ligand solubility in non-polar solvent contribute to render CsPbBr3 particularly sensitive to environmental and processing conditions and, therefore prone to undergo to structural, morphological and, hence spectroscopic, transformations.
关键词： lead halide perovskite nanocrystals,surface chemistry,ligands equilibria,long term stability
更新于2025-11-21 11:01:37
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General Synthesis of Ordered Mesoporous Rare-Earth Orthovanadate Thin Films and Their Use as Photocatalysts and Phosphors for Lighting Applications
摘要： Herein, the block copolymer templating sol-gel synthesis of a novel class of ternary oxide nanomaterials is reported. NdVO4, EuVO4, GdVO4, DyVO4, YVO4, and TmVO4 have been prepared as open mesoporous films by the dip-coating method using hydrated rare-earth nitrate salt precursors along with vanadium oxytrichloride. All materials crystallize in the tetragonal ZrSiO4-type structure with space-group I41/amd. Short-term treatment at 550 °C is found sufficient to initiate crystallization. Characterization via X-ray and electron diffraction, Raman and X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry confirms the single-phase nature and uniformity of the different orthovanadates with tailorable crystallite sizes. The integrated results from electron and atomic force microscopy, Kr-physisorption as well as in-situ and ex-situ synchrotron-based small-angle X-ray scattering reveal that the porosity persists throughout the thickness of films and the mesoscopic ordering is retained even after heating in air at 700 °C. Photobleaching experiments indicate that the sol-gel derived materials, showing an indirect band gap transition at (3.8±0.1) eV, exhibit good photocatalytic properties—the activity is highly superior to that of bulk films of the same nominal composition. Moreover, when doping GdVO4, YVO4, and solid solution GdVO4-YVO4 with trivalent rare-earth ions such as Eu3+, Dy3+, Er3+, or Tm3+ ions, the films hold promise as phosphors for lighting applications, which might pave the way toward development of (3-dimensional) intricate nanocomposites with unprecedented functionalities.
关键词： Block copolymer templating,ternary metal oxide nanostructure,photocatalyst,phosphor,sol-gel chemistry
更新于2025-11-21 10:59:37
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Introducing Manganese-Doped Lead Halide Perovskite Quantum Dots: A Simple Synthesis Illustrating Optoelectronic Properties of Semiconductors
摘要： Quantum dots (QDs) are considered useful for demonstrating quantum phenomena in undergraduate laboratories due to their monodisperse size and excellent optical properties. Although doping has an increasingly important role in QD fabrication in the semiconductor field, it has rarely been discussed in the context of the undergraduate laboratory. In this work, a simple synthesis and characterization method for Mn-doped CsPbCl3 QDs for an upper-level undergraduate inorganic chemistry laboratory is reported. The Mn-doped CsPbCl3 system benefits from a simplified synthesis and straightforward characterization. This experiment introduces QD research to students and offers opportunities for instructors to discuss many important concepts in inorganic chemistry, such as energy band theory, particle-in-a-box model, electron paramagnetic resonance, ligand field theory, and nanochemistry.
关键词： Inorganic Chemistry,Crystal Field/Ligand Field Theory,EPR/ESR Spectroscopy,Upper-Division Undergraduate,Hands-On Learning/Manipulatives,Laboratory Instruction,Nanotechnology
更新于2025-11-20 15:33:11
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Tuning the Functional Groups on Carbon Nanodots and Antioxidant Studies
摘要： Carbon nanodots (CNDs) have shown good antioxidant capabilities by scavenging oxidant free radicals such as diphenyl-1-picrylhydrazyl radical (DPPH?) and reactive oxygen species. While some studies suggest that the antioxidation activities associate to the proton donor role of surface active groups like carboxyl groups (–COOH), it is unclear how exactly the extent of oxidant scavenging potential and its related mechanisms are influenced by functional groups on CNDs’ surfaces. In this work, carboxyl and the amino functional groups on CNDs’ surfaces are modified to investigate the individual influence of intermolecular interactions with DPPH? free radical by UV-Vis spectroscopy and electrochemistry. The results suggest that both the carboxyl and the amino groups contribute to the antioxidation activity of CNDs through either a direct or indirect hydrogen atom transfer reaction with DPPH?.
关键词： carbon nanodots,radical scavenging,electro-chemistry,functional groups,antioxidation,charge transfer
更新于2025-11-19 16:56:35
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Synchronized “Click” and Templated Synthesis of a Fluorescent Pyrene Crown Ether
摘要： The reaction of 6,8-bisethynylpyrene-2-carboxylic acid methyl ester with 1-azido-2-(2-(2-azidoethoxy)ethoxy)ethoxy)ethane using standard “click” chemistry produced a 1+1 crown ether (CPYR). The copper ions used both catalyse the reaction and provide a template for ensuring smooth cyclisation. The X-ray crystal structure of the compound reveals the two triazole groups are non-coplanar with the pyrene moiety. The triazole groups are more co-planar with the pyrene subunit in the first-excited singlet state as revealed by a density functional theory (DFT) calculated molecular structure (B3LYP, 6-311G). Partially structured emission observed in acetonitrile is consistent with the calculation result. In acetonitrile solution the macrocycle CPYR interacts with a Na+ ion to form a complex in which the ion binds with the crown and the pyrene residue.
关键词： pyrene,structure,click,binding,crown ether
更新于2025-11-19 16:46:39
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Effect of counter-surface chemistry on defect-free material removal of monocrystalline silicon
摘要： To bring light on material removal remains fundamental for promoting the advancement of nanotechnology. In this study, nanoscratching test on silicon surface against Al2O3 microsphere was performed using an atomic force microscope, and the material removal by SiO2 microsphere sliding was taken as a comparison. It was found that nanochannels can be produced on silicon surface by Al2O3 microsphere scratching under much lower contact pressure than the yield limit for plastic deformation, which can be ascribed to water-participated tribochemical reactions. The tribochemical removal was verified by high resolution transmission electron microscope (HRTEM) detection. Further analysis indicates that the tribochemical reactions on silicon surface are strongly affected by the counter-surface chemistry. It is noted that counter-surface chemistry influences the tribochemical reactions via altering the activation energy barrier for forming bonding bridge, and has little influence on decreasing the activation energy barrier for the rupture of Si-Si backbonds in silicon substrate. Compared with SiO2 tip, Al2O3 tip has longer working life span, and the nanochannels fabricated by Al2O3 tip under the same processing conditions exhibit better uniformity even in KOH solution. The results provide useful knowledge for chemical mechanical polishing and tip-based nanomanufacturing processes, and shed new light for enriching the basic theory of nanotribology.
关键词： Tribochemical removal,Nanoscratching,Counter-surface chemistry,Alumina/silicon pair
更新于2025-11-14 17:03:37
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Room Temperature Synthesis of Germanium Oxide Nanofilaments and Their Potential Use as Luminescent Self‐Cleaning Surfaces
摘要： Germanium oxide nanofilaments (GNFs) have been synthesized under ambient conditions from the gas phase using germanium tetrachloride as a precursor. Non-crystalline GNFs synthesized by this procedure are 1-10 μm in length and 80-110 nm in diameter applying Droplet Assisted Growth and Shaping (DAGS) Chemistry. The relative humidity has been adjusted at various values in order to demonstrate the crucial role of humidity in the gas phase for the nanofilament synthesis. The novel GNFs show a strong luminescence emission in the ultra-violet and light blue region. In addition, a self-cleaning and superhydrophobic properties could be introduced in the luminescent GNF nanofilaments by simple treatment with silane molecules.
关键词： silicone nanofilaments,chemical vapor deposition,DAGS chemistry,germanium oxide nanofilaments,self-cleaning surfaces
更新于2025-11-14 15:18:02
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Polysiloxane-based Hyperbranched Fluorescent Materials Prepared by Thiol-ene “Click” Chemistry as Potential Cellular Imaging Polymers
摘要： Hyperbranched polymers have attracted increasing interest due to their unique properties which possess excellent RI and thermal stability, and have been widely used in fields of drug delivery, catalysts, liquid crystal and so on. Herein, polysiloxane-based hyperbranched fluorescent materials (P1 and P2) were synthesized by thiol-ene “click” chemistry. Then, novel polysiloxane-based hyperbranched fluorescent materials (P1-Ln3+) has been prepared by rare earth ions coordination. In view of the splendid fluorescence characteristics and favorable stability of P1-Ln3+, it has been applied in biological imaging. P1-Ln3+ has gained commendable applications in bioimaging.
关键词： Fluorescence materials,Living cells imaging,Hyperbranched polymers,Thiol-ene "click" chemistry,Coordination,Rare earth ions
更新于2025-09-23 15:23:52
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The role of dipole structure and their interaction on the electromechanical and actuation performance of homogeneous silicone dielectric elastomers
摘要： Grafting polar groups onto elastomer chains has proven to be an effective method to achieve high performance homogenous dielectric elastomers (DE). Up to now, there still lacks an in-depth understanding of the effect of structure and content of these grafted dipoles on the electromechanical properties of the modified DE. In this study, three kinds of polar groups including carboxyl (COOH), hydroxyl (OH), and ester (COOCH3) are grafted onto Polymethylvinylsiloxane (PMVS) by using a photochemical thiol-ene reaction to prepare PMVS-COOH, PMVS-OH and PMVS-COOCH3 DE. Three grafting degrees (15%, 50% and 95%) were prepared for each kind of modified PMVS. Interestingly, although the dipolar moment of COOH is higher than that of OH and COOCH3, at the same grafting degree, the dielectric constant of PMVS-OH is much higher than that of PMVS-COOCH3 and PMVS-COOH. At high grafting degree (50% and 95%), the actuated strain at a specific electric field of PMVS-OH is significantly higher than that of PMVS-COOH and PMVS-COOCH3. The actuated train at a 15 kV/mm sharply increases from 0.2% for PMVS to 9.1% for PMVS-OH with the grafting degree of 95%, higher than that of the commercial silicone DE and the new structured silicone DE reported previously. These dielectric, mechanical and actuated properties are affected by the combined effects of moment, mobility and interactions of these dipoles, which have been deeply discussed. The present study provides guidance for the preparation of high-performance homogeneous DE by rational designing the dipolar structure and content.
关键词： Polymethylvinylsiloxane,dipoles,electromechanical properties,thiol-ene click chemistry,dielectric elastomers,actuated strain
更新于2025-09-23 15:23:52