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Nanostructures of functionalized zinc phthalocyanines prepared with colloidal lithography: Evaluation of surface orientation and dimensions using scanning probe microscopy
摘要： Patterned arrays of nanoholes and nanorings were prepared using colloidal lithography combined with steps of solution immersion and vapor deposition of organosilanes. Samples prepared with colloidal lithography exhibit millions of reproducible test structures with a periodic arrangement throughout areas of the surface according to the dimensions and spacing of the particle mask. Views of the size and morphology of nanopatterns obtained with atomic force microscopy (AFM) can provide information of progressive steps of chemical reactions as nanostructures are grown within spatially confined areas surrounded by a resist film. A surface mask of colloidal latex or silica spheres was used to protect discrete areas of a Si(111) substrate from the deposition of organosilanes. When the mask was removed, the uncovered areas of the surface revealed regularly-shaped, small sites of uncovered substrate available for further reaction steps to build hierarchical surface structures. Nanostructures of zinc phthalocyanines (ZnPcs) were constructed using amine-terminated nanopatterns as sites for binding. Spatial selectivity was achieved for directing the attachment of ZnPcs to the surface using resist films of 2-[methoxy(polyethyleneoxy)propyl]trichlorosilane (PEO-silane) and also with octadecyltrimethoxysilane (OTMS). The molecule chosen as a linker was (3-aminopropyl)triethoxysilane (APTES) which presents an amine group at the interface. In general, phthalocyanine molecules tend to bind in a coplanar orientation by physisorption to the surface and can stack together through pi-pi interactions between adjacent macrocycles. However, the nature of the substituents will also influence whether the molecules assemble on surfaces in a side-on orientation or with the macrocycle oriented in a coplanar arrangement. Hydroxyl and isothiocyanate pendant groups were attached to the macrocycles of ZnPcs chosen for this study, to investigate conformational differences when attached to APTES nanopatterns. The size and morphology of nanostructures was visualized and sensitively measured with tapping-mode AFM. The elastic response of samples patterned with ZnPc was mapped with force modulation AFM. Changes in the height of nanostructures indicate whether the macrocycles are oriented upright or parallel to the surface plane, or if multilayers were formed.
关键词： Atomic force microscopy,Colloidal lithography,Nanopatterning,Phthalocyanines
更新于2025-09-23 15:19:57
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Interaction-tailored organization of large-area colloidal assemblies
摘要： Colloidal lithography is an innovative fabrication technique employing spherical, nanoscale crystals as a lithographic mask for the low cost realization of nanoscale patterning. The features of the resulting nanostructures are related to the particle size, deposition conditions and interactions involved. In this work, we studied the absorption of polystyrene spheres onto a substrate and discuss the effect of particle–substrate and particle–particle interactions on their organization. Depending on the nature and the strength of the interactions acting in the colloidal film formation, two different strategies were developed in order to control the number of particles on the surface and the interparticle distance, namely changing the salt concentration and absorption time in the particle solution. These approaches enabled the realization of large area (≈cm2) patterning of nanoscale holes (nanoholes) and nanoscale disks (nanodisks) of different sizes and materials.
关键词： localized surface plasmon resonance,large-area nanostructure patterning,colloidal lithography,spherical nanoparticles,electrostatic interactions
更新于2025-09-19 17:15:36
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Exploring the surface chemistry of cesium lead halide perovskite nanocrystals
摘要： Colloidal nanocrystals (NCs) of cesium lead halide perovskites (CsPbX3, X = Cl, Br or I) are emerging as an exciting class of optoelectronic materials, but the retention of their colloidal and structural integrity during isolation, purification and handling still represents a critical issue. The impelling questions concerning their intrinsic chemical instability are connected to the dynamic nature of the bonding between the inorganic surface and the long-chain capping ligands. However, the key aspects of CsPbX3's surface chemistry that directly impact their stability remain elusive. In this contribution, we provide an in-depth investigation of the surface properties of differently composed CsPbX3 NCs, prepared by traditional hot-injection methods. The study, mainly relying on solution NMR spectroscopy, is backed up by elemental analysis as well as morphological, structural and optical investigations. We ascertained that the nature of the ligand adsorption/desorption processes at the NC surface is dependent on its elemental composition, thus explaining the origin of the instability afflicting CsPbI3 NCs. We also evaluated the effect of NC purification as well as of the degradation pathways involving the organic shell on the surface chemistry of CsPbX3 NCs. This study paves the way for new post-functionalization strategies for this promising class of nanomaterials.
关键词： surface chemistry,colloidal stability,degradation pathways,cesium lead halide perovskite nanocrystals,purification,ligand adsorption/desorption,NMR spectroscopy
更新于2025-09-19 17:15:36
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Electric field-directed assembly of fullerene crystal rods into hierarchical films
摘要： Self-assembly of nanomaterials with desired material properties requires assembly control from nanometer to millimeter scales. Here, hierarchical C60 and C70 films are assembled from the nanoscale to macroscale by combining co-solvent precipitation with electric-field directed assembly. Fullerene molecular crystals are grown via seeded co-solvent precipitation with mixed organic solvents and antisolvent 2-propanol. Rods of varying aspect ratios (1.7, 2 and 3.7) are prepared as a function of injection volume, fullerene type and solution concentration. Electric fields are applied to colloidal fullerene rods confined to two dimensions. The applied field induces dipolar forces, dielectrophoretic forces, and electrohydrodynamic flows. Frequency-dependent phase transitions occur at the critical Maxwell–Wagner crossover frequency, where the effective polarizability of the particles in the medium is substantially reduced, resulting in changes in structure. Partial order phases form as a function of field strength, frequency, and confinement including tetratic, smectic, centered rectangular and string fluids.
关键词： colloidal rods,electric field,fullerene,hierarchical films,self-assembly
更新于2025-09-19 17:15:36
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Light-Gated Synthetic Protocells for Plasmon-Enhanced Chemiosmotic Gradient Generation and Phosphorylation
摘要： Here, we present the construction of a light-gated protocell model made of plasmonic colloidal capsules (CCs) assembled with lipoprotein bacteriorhodopsin for converting solar energy into electrochemical gradients and further driving synthesis of energy storage molecules. Not only did this synthetic protocell incorporate essential features of CCs, but it also assimilated such an important intrinsic property of noble metal colloidal particles as plasmonic resonance. Specially, the near-field coupling between adjacent metal nanoparticles gave rise to strongly localized electric fields and resulted in a broad absorption in the whole visible spectra, which in turn promoted to bacteriorhodopsin and accelerated the proton pumping kinetics. The cell-like potential of this design was further demonstrated by leveraging the outward pumped protons as 'chemical signals' for triggering ATP biosynthesis in a coexistent synthetic protocell population. Hereby, we lay the groundwork for engineering of colloidal supraparticle-based synthetic protocells with higher-order functionalities.
关键词： protocell,colloidal capsule,bacteriorhodopsin,plasmonic resonance,chemiosmotic gradient
更新于2025-09-19 17:15:36
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Natural organic matter inhibits aggregation of few-layered black phosphorus in mono- and divalent electrolyte solutions
摘要： Extensive synthesis and applications of few-layered black phosphorus (BPs) are accompanied by increasing concern over its stability and potential risk. However, the colloidal stability of BPs under environmentally relevant conditions remains unclear. Hence, we investigated the influences of two representative electrolytes (i.e., NaCl and CaCl2) and natural organic matter (NOM) on the aggregation behavior of BPs. Ca2+ ions exhibited a stronger destabilization effect on BPs than Na+ due to their stronger surface charge screening as well as intersheet bridging by the complexes of Ca2+ ions and oxidized phosphorus (POx) species on the BPs surface. Apart from the Ca2+-induced enhanced aggregation in the presence of high concentration of Ca2+, the aggregation behavior of BPs in the two electrolytes at different concentrations and their ratios of critical coagulation concentrations (CCCs) generally followed classical colloidal theory such as the Schulze–Hardy rule. Moreover, in the presence of 10 mg C/L NOM the CCC values of BPs in NaCl and CaCl2 solutions were both three times higher than that obtained without NOM, and the aggregation kinetics of BPs in these electrolytes containing NOM were qualitatively consistent with extended DLVO theory. Specifically, NOM significantly improved the stabilization of BPs in CaCl2 solutions via steric repulsion and isolation of Ca2+ ions from interaction with POx species on the surface of BPs. This stabilization mechanism derived from “NOM corona” structures was elucidated by a wide spectrum of characterization and quantification techniques. These findings provide new insights into evaluating the stability and fate of this nanomaterial in natural aquatic environments.
关键词： few-layered black phosphorus,colloidal stability,NOM corona,aggregation,electrolytes,natural organic matter
更新于2025-09-19 17:15:36
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Solid-State Encapsulation and Color Tuning in Films of Cesium Lead Halide Perovskite Nanocrystals for White Light Generation
摘要： Perovskite nanocrystals (PNCs) are highly demanding nanomaterials for solid-state lighting applications. A challenge for their exploitation in practical applications is the insufficient ambient and water stability associated with their ionic nature. Here we report a novel route for solid-state encapsulation of films of perovskite nanocrystals (PNCs) through vapor-phase deposition of a thin and hydrophobic layer of fluoroalkyltrichlorosilanes (FAS). High quality nanoscale crystals of CsPbBr3 were synthesized with well-established colloidal methods and coated on solid substrates. The films of PNCs were then subjected to vapor of FAS for short durations of time (<60 s) in ambient atmosphere resulting in deposition of a thin (< 20 nm) hydrophobic layer. Besides providing a barrier for water and humidity, the vapor-phase deposition of FAS was accompanied with the blue-shift of the emission wavelength of the PNCs. The color shift results from the exchange of Br with Cl anions, which emerge during the self-hydrolysis of the silane molecules. Throughout this process, we demonstrate the enhanced water stability of the films of PNCs and fine tunability of the wavelength in films from 516 nm to 488 nm. The fabrication of a white light emitting diode and tunability of the color coordinates with the duration of the FAS deposition was demonstrated. The rapid, scalable, and inexpensive solid-state encapsulation approach shows great promise for films of halide perovskites.
关键词： perovskite nanocrystals,vapor-phase deposition,trichlorosilane,colloidal optoelectronics
更新于2025-09-19 17:15:36
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Collective topo-epitaxy in the self-assembly of a 3D quantum dot superlattice
摘要： Epitaxially fused colloidal quantum dot (QD) superlattices (epi-SLs) may enable a new class of semiconductors that combine the size-tunable photophysics of QDs with bulk-like electronic performance, but progress is hindered by a poor understanding of epi-SL formation and surface chemistry. Here we use X-ray scattering and correlative electron imaging and diffraction of individual SL grains to determine the formation mechanism of three-dimensional PbSe QD epi-SL films. We show that the epi-SL forms from a rhombohedrally distorted body centred cubic parent SL via a phase transition in which the QDs translate with minimal rotation (~10°) and epitaxially fuse across their {100} facets in three dimensions. This collective epitaxial transformation is atomically topotactic across the 103–105 QDs in each SL grain. Infilling the epi-SLs with alumina by atomic layer deposition greatly changes their electrical properties without affecting the superlattice structure. Our work establishes the formation mechanism of three-dimensional QD epi-SLs and illustrates the critical importance of surface chemistry to charge transport in these materials.
关键词： superlattice,atomic layer deposition,topotaxy,PbSe,colloidal quantum dot,epitaxial fusion
更新于2025-09-19 17:13:59
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Study of the physicochemical surface alterations and incubation phenomena induced on iron targets by nanosecond pulsed laser ablation in liquids: Effect on productivity and characteristics of the synthesized nanoscale zero-valent iron (nZVI) particles
摘要： This work presents a systematic study of the significant role of the surface physicochemical alterations produced during the laser ablation of massive iron disks submerged in different solvents on the generation of colloidal iron nanoparticles. For that purpose, the laser ablation thresholds and the incubation coefficients for various pulse numbers per site and pulse energies have been measured under distilled water (DW) and ethanol (EtOH). After that, a complete physicochemical characterization of these targets indicated higher threshold fluence values for the ablation experiments conducted in EtOH than those performed in DW. The threshold fluence values decreased also with the decrease of the pulse overlap for both solvents, being it much more pronounced in EtOH. In addition, the related incubation coefficient showed that the incubation effect is lower for experiments conducted in DW. The characteristics of the synthesized nZVI particles were also a function of the solvent nature and the pulse overlap: laser ablation in DW leaded to iron oxide nanoparticles, whereas core-shell iron nanoparticles were obtained in EtOH. Moreover, high pulse overlap values lead to chemical alterations, resulting in a decrease of the composition homogeneity and a strong increase of the nanoparticle polydispersity.
关键词： Incubation effect,Nanosecond pulsed laser ablation in liquids,Raman spectroscopy,Colloidal nanoscale zero-valent iron particles,Laser ablation threshold,Laser induced-chemical surface alteration
更新于2025-09-19 17:13:59
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PbE (E = S, Se) Colloidal Quantum Dot-Layered 2D Material Hybrid Photodetectors
摘要： Hybrid lead chalcogenide (PbE) (E = S, Se) quantum dot (QD)-layered 2D systems are an emerging class of photodetectors with unique potential to expand the range of current technologies and easily integrate into current complementary metal-oxide-semiconductor (CMOS)-compatible architectures. Herein, we review recent advancements in hybrid PbE QD-layered 2D photodetectors and place them in the context of key findings from studies of charge transport in layered 2D materials and QD films that provide lessons to be applied to the hybrid system. Photodetectors utilizing a range of layered 2D materials including graphene and transition metal dichalcogenides sensitized with PbE QDs in various device architectures are presented. Figures of merit such as responsivity (R) and detectivity (D*) are reviewed for a multitude of devices in order to compare detector performance. Finally, a look to the future considers possible avenues for future device development, including potential new materials and device treatment/fabrication options.
关键词： photodetectors,phosphorene,infrared,PbS,graphene,layered 2D materials,TMDs,colloidal quantum dots,PbSe
更新于2025-09-19 17:13:59