Nucleation Of Nanocrystals Research Articles

Tuning Perovskite Nanocrystal Synthesis via Amphiphilic Block Copolymer Templates and Solvent Interactions.

Amphiphilic block copolymer (a-BCP) micelles offer morphological diversity and dimensional tunability, making them suitable for the fabrication of perovskite nanocrystals. However, precise control over the nucleation and growth of perovskite nanocrystals using a-BCP colloidal templates remains underexplored. This study investigates the effects of toluene, methanol, and polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) on the formation of cesium lead bromide (CsPbBr3) nanocrystals. The process involves four stages: (i) PS-b-P2VP micellization, (ii) PbBr2 complexation, (iii) coordination interaction with P2VP, and (iv) burst nucleation of CsPbBr3 nanocrystals. Toluene, a good solvent for PS but a nonsolvent for P2VP, PbBr2, and CsBr, facilitates the formation of PS-b-P2VP spherical micelles. Adding PbBr2 to these micelles in toluene results in multiple emulsion, dispersing PbBr2 microstructures (microemulsion) and forming [PbBr3]- complexes encapsulated by the micelles (nanoemulsion). Prolonged stirring enhances this nanoemulsion. CsBr, insoluble in toluene, must be dissolved in methanol before being mixed with micelle-encapsulated complexes, promoting quick crystal nucleation. However, excess methanol weakens micellization, leading to the formation of fused micelles and irregular nanocrystals. At a high methanol content, [PbBr4]2- complexes also form, driving CsPbBr3 to CsPb2Br5 transformation via Ostwald ripening, resulting in large CsPb2Br5 microcrystals that precipitate due to gravitational forces overcoming Brownian motion, destabilizing their dispersion in the solution.

In situ growth of ZIF-8 on cellulose microspheres with high doxorubicin loading capacity and pH-sensitive for oral drug delivery

Metal-organic framework (MOF) nanoparticles are a class of porous nanomaterials with wide application prospects. Zeolitic imidazolate framework (ZIF) materials have high loading performance and pH-sensitive characteristics, which means they have great development prospects in the development of drug carrier systems. Herein, cellulose microspheres (CM) were used as a carrier for the nucleation and growth of ZIF-8 nanocrystals. CM@ZIF-8 was prepared in situ, which was more convenient, flexible, cost-effective, and highly safe. CM@ZIF-8, as a novel carrier, was used to monitor the release of the anticancer drug Doxorubicin (DOX) and prevent it from dissipating before reaching its goal. The designed DOX-loaded CM@ZIF-8 (CM@ZIF-8-DOX) system was characterized by FTIR, SEM, N2 sorption isotherm, XRD, and Cytotoxicity assay (cells survival rate 95.08 %). CM@ZIF-8-DOX exhibited controlled drug release behavior in simulated in-vitro tumor microenvironments (81.2 % drug release throughout 72h). CM@ZIF-8 simultaneously had a high loading capacity of DOX (Qe = 159.71 mg∙g−1), and the amount released under acidic conditions (pH 5.0) was greater (63.4 % after 15 h) than under neutral conditions (pH 7.4) due to the detachment of the coordination between metal ions and ligands (37.6 % after 15 h).

Simulation of doubly stochastic Poisson point processes and application to nucleation of nanocrystals and evaluation of exciton fluxes

Abstract In this study we solve the following problem: Simulate random 2D Poisson point processes with a desired correlation function. To solve this problem we suggest the following algorithm: (1) simulate a positive valued random process with the desired correlation function, (2) use this process as an intensity of the doubly stochastic Poisson random point process. We apply this algorithm to simulate random distribution of nanocrystals on a plane. Then we apply the developed methods to calculate excitonic fluxes to the family of generated nanocrystals.

Bipyramidal Nanocrystals of Noble Metals: From Synthesis to Applications.

Shape control has been a major theme of nanocrystal research in terms of synthesis, property tailoring, and optimization of performance in a variety of applications. Among the possible shapes, bipyramids are unique owing to their symmetry, planar defects, and exposed facets. In this article, we focus on the colloidal synthesis of noble-metal nanocrystals featuring a triangular bipyramidal shape, together with highlights of their properties and applications. We start with a brief discussion of the general classification and requirements for the nucleation and growth of bipyramidal nanocrystals, followed by specific aspects regarding the synthetic methods with a focus on the roles of reduction, etching, and capping, as well as controls of facet, size, aspect ratio, and corner truncation. In the end, we illustrate how these aspects affect the properties of bipyramidal nanocrystals for plasmonic and catalytic applications, together with future perspectives.

In Situ Visual Observation of Surface Energy-Controlled Heterogeneous Nucleation of Metal Nanocrystals.

Electrochemical growth of metal nanocrystals is pivotal for material synthesis, processing, and resource recovery. Understanding the heterogeneous interface between electrolyte and electrode is crucial for nanocrystal nucleation, but the influence of this interaction is still poorly understood. This study employs advanced in situ measurements to investigate the heterogeneous nucleation of metals on solid surfaces. By observing the copper nanocrystal electrodeposition, an interphase interaction-induced nucleation mechanism highly dependent on substrate surface energy is uncovered. It shows that a high-energy (HE) electrode tended to form a polycrystalline structure, while a low-energy (LE) electrode induced a monocrystalline structure. Raman and electrochemical characterizations confirmed that HE interface enhances the interphase interaction, reducing the nucleation barrier for the sturdy nanostructures. This leads to a 30.92-52.21% reduction in the crystal layer thickness and a 19.18-31.78% increase in the charge transfer capability, promoting the formation of a uniform and compact film. The structural compactness of the early nucleated crystals enhances the deposit stability for long-duration electrodeposition. This research not only inspires comprehension of physicochemical processes correlated with heterogeneous nucleation, but also paves a new avenue for high-quality synthesis and efficient recovery of metallic nanomaterials.

A General Nucleation Model for Semiconductor Nanocrystals.

We introduce a nonclassical model for nanocrystal nucleation in solution which centers on the dynamic interplay of chemical bond breakage and formation coupled with the desolvation of precursor molecules, which we term the molecular chemistry (MC) model. Departing from classical theory, our model employs the bond count as the key variable rather than particle size, thereby redefining the role of supersaturation and its role in determining the so-called critical nucleus size. We apply the model to CdSe nanocrystal formation in nonpolar solvents and showcase its efficacy in predicting solvent dynamics, precursor characteristics, crystal phase, stoichiometry, "magic number" behavior, and transition states. While the coupled-cluster method is used to determine the bond energy, we show that it is possible to derive reaction pathways by reducing the calculations to algebraic approximations for the nucleation energy. This singular set of bond energy parameters allows nanocrystal nucleation and growth to be conceptualized as a straightforward chemical reaction.

Interrogation of 3d Transition Bimetallic Nanocrystal Nucleation and Growth Using In Situ Electron Microscope and Synchrotron X-ray Techniques.

Understanding the nucleation and growth mechanism of 3d transition bimetallic nanocrystals (NCs) is crucial to developing NCs with tailored nanostructures and properties. However, it remains a significant challenge due to the complexity of 3d bimetallic NCs formation and their sensitivity to oxygen. Here, by combining in situ electron microscopy and synchrotron X-ray techniques, we elucidate the nucleation and growth pathways of Fe-Ni NCs. Interestingly, the formation of Fe-Ni NCs emerges from the assimilation of Fe into Ni clusters together with the reduction of Fe-Ni oxides. Subsequently, these NCs undergo solid-state phase transitions, resulting in two distinct solid solutions, ultimately dominated by γ-Fe3Ni2. Furthermore, we deconvolve the interplays between local coordination and electronic state concerning the growth temperature. We directly visualize the oxidation-state distributions of Fe and Ni at the nanoscale and investigate their changes. This work may reshape and enhance the understanding of nucleation and growth in atomic crystallization.

Electric Field Effects in Flash Joule Heating Synthesis.

Flash Joule heating has emerged as an ultrafast, scalable, and versatile synthesis method for nanomaterials, such as graphene. Here, we experimentally and theoretically deconvolute the contributions of thermal and electrical processes to the synthesis of graphene by flash Joule heating. While traditional methods of graphene synthesis involve purely chemical or thermal driving forces, our results show that the presence of charge and the resulting electric field in a graphene precursor catalyze the formation of graphene. Furthermore, modulation of the current or the pulse width affords the ability to control the three-step phase transition of the material from amorphous carbon to turbostratic graphene and finally to ordered (AB and ABC-stacked) graphene and graphite. Finally, density functional theory simulations reveal that the presence of a charge- and current-induced electric field inside the graphene precursor facilitates phase transition by lowering the activation energy of the reaction. These results demonstrate that the passage of electrical current through a solid sample can directly drive nanocrystal nucleation in flash Joule heating, an insight that may inform future Joule heating or other electrical synthesis strategies.

Bifunctional MNPs@UIO-66-Arg core-shell-satellite nanocomposites for enrichment of phosphopeptides.

A facile and mild method based on self-assembled lysozyme (LYZ) to fabricate bifunctional MNPs@UIO-66-Arg core-shell-satellite nanocomposites (CSSNCs) is reported for the high-efficiency enrichment of phosphopeptides. Under physiological conditions, LYZ rapidly self-assembled into a robust coating on Fe3O4@SiO2 magnetic nanoparticles (MNPs) with abundant surface functional groups, which effectively mediate heterogeneous nucleation and growth of UIO-66 nanocrystals. Well-defined MNPs@UIO-66 CSSNCs with stacked pores, showing high specific surface area (333.65 m2 g- 1) and low mass transfer resistance, were successfully fabricated by fine-tuning of the reaction conditions including reaction time and acetic acid content. Furthermore, the UIO-66 shells were further modified with arginine to obtain bifunctional MNPs@UIO-66-Arg CSSNCs. Thanks to the unique morphology and synergistic effect of Zr-O clusters and guanidine groups, the bifunctional MNPs@UIO-66-Arg CSSNCs exhibited outstanding enrichment performance for phosphopeptides, delivering a low limit of detection (0.1 fmol), high selectivity (β-casein/BSA, mass ratio 1:2000), and good capture capacity (120 mg g- 1). The mechanism for phosphopeptides capture may attribute to the hydrogen bonds, electrostatic interactions, and Zr-O-P bonds between phosphate groups in peptides and guanidyl/Zr-O clusters on bifunctional MNPs@UIO-66-Arg CSSNCs. In addition, the small stacking pores on the core-shell-satellite architecture may selectively capture phosphopeptides with low molecular weight, eliminating interference of other large molecular proteins in complex biological samples.

Heterogeneous Coprecipitation of Nanocrystals with Metals on Substrates.

ConspectusThe heterogeneous coprecipitation of nanocrystals with metals on substrates plays a significant role in both natural and engineered systems. Due to the small dimensions and thereby the large specific surface area, nanocrystal coprecipitation with metals, which is ubiquitous in natural settings, exerts drastic effects on the biogeochemical cycling of metals on the earth's crust. Meanwhile, the controlled synthesis of nanocrystals with metal doping to achieve tunable size/composition enables their broad applications as adsorbents and catalysts in many engineered settings. Despite their importance, complex interactions among aqueous ions/polymers, nanocrystals, substrates, and metals are far from being well-understood, leaving the controlling mechanisms for nanocrystal formation with metals on substrates uncovered.In this Account, we discuss our systematic investigation over the past 10 years of the heterogeneous formation of representative nanocrystals with metals on typical substrates. We chose Fe(OH)3 and BaSO4 as representative nanocrystals. Mechanisms for varied metal coprecipitation were also investigated for both types of nanocrystals (i.e., Fe, Al, Cr, Cu, and Pb)(OH)3 and (Ba, Sr)(SO4, SeO4, and SeO3)). Bare SiO2 and Al2O3, as well as those coated with varied organics, were selected as geologically or synthetically representative substrates. Through the integration of state-of-the-art nanoscale interfacial characterization techniques with theoretical calculations, the complex interactions during nanocrystal formation at interfaces were probed and the controlling mechanisms were identified.For BaSO4 and Fe(OH)3 formation on substrates, the local supersaturation levels near substrates were controlled by Ba2+ adsorption and the electrostatic attraction of Fe(OH)3 monomer/polymer to substrates, respectively. Meanwhile, substrate hydrophobicity controlled the interfacial energy for the nucleation of both nanocrystals on (in)organic substrates. Metal ions' (i.e., Cr/Al/Cu/Pb) hydrolysis constants and substrates' dielectric constants controlled metal ion adsorption onto substrates, which altered the surface charges of substrates, thus controlling heterogeneous Fe(OH)3 nanocrystal formation on substrates by electrostatic interactions. The sizes and compositions of heterogeneous (Fe, Cr)(OH)3 and (Ba, Sr)(SO4, SeO4, SeO3) formed on substrates were found to be distinct from those of homogeneous precipitates formed in solution. The substrate (de)protonation could alter the local solution's pH and the substrates' surface charge; substrates could also adsorb cations, affecting local Fe/Cr/Ba/Sr ion concentrations at solid-water interfaces, thus controlling the amount/size/composition of nanocrystals by tuning their nucleation/growth/deposition on substrates. From slightly supersaturated solution, homogeneous coprecipitates of microsized (Ba, Sr)(SO4, SeO4, SeO3) formed through growth, with little Sr/Se(VI) incorporation due to higher solubilities of SrSO4 and BaSeO4 over BaSO4. While cation enrichment near substrates made the local solution highly supersaturated, nanosized coprecipitates formed on substrates through nucleation, with more Sr/Se(VI) incorporation due to lower interfacial energies of SrSO4 and BaSeO4 over BaSO4. The new insights gained advanced our understanding of the biogeochemical cycling of varied elements at solid-water interfaces and of the controlled synthesis of functional nanocrystals.

Atomic scale formation mechanism of the Amorphous-Nanocrystalline biphase structure in TiSiN Coating: Phase field crystal simulation and experimental characterization

TiSiN nanocomposite coatings have exceptional strength, toughness, and corrosion resistance due to their unique biphase amorphous/nanocrystalline structure with tiny TiN grains embedded in an amorphous Si3N4 phase. However, the unclear formation process makes microstructural control challenging. In this study the phase field crystal method has been employed to analyze the microstructure evolution in TiSiN coatings, uncovering a four-step formation mechanism for the amorphous-nanocrystalline structure. The initial stage results in appearance of concentration heterogeneities and the development of the triangular-like short-range order (Stage I). This stage is followed by the nucleation of nanocrystals in Ti-rich zones and the transformation of triangular short-range to the long-range order with a square symmetry (Stage II). Then, during coarsening stage, Ti-rich polycrystalline nanocrystals are formed (Stage Ⅲ) followed by the vacancy migration from the polycrystalline nanocrystals to amorphous phase and formation of monocrystalline Ti nanocrystals embedded in amorphous phase (Stage Ⅳ). The simulation results are compared qualitatively with aberration-corrected High-Resolution Scanning Transmission Electron Microscopy and High-Resolution Transmission Electron Microscopy images from our study.

Ultrasound-assisted nucleation and growth of hydroxyl-protected and ligand-free Cs3Cu2X5 nanocrystals with bright luminescence.

The commercial applications of lead halide perovskites are hindered by their negative environmental impact and inherent instability. Consequently, developing environmentally friendly copper-based perovskite materials is crucial for future solid-state lighting and display applications. In this study, an ultrafast high-power ultrasonic synthesis strategy was utilized to achieve uniform nucleation and growth of Cs3Cu2X5 (X = Cl, Br, I) nanocrystals (NCs) that possess remarkable luminescence properties, hydroxyl protection, and ligand-free characteristics. These Cs3Cu2X5 NCs exhibited a tunable spectral range spanning from 446 to 525 nm, accompanied by photoluminescence quantum yields (PLQYs) varying from 0.2% to 79.2%. The spectral attributes of the NCs were effectively controlled by modulating the halide type and composition. It is worth noting that density functional theory (DFT) calculations offer valuable insights into the synthesis of NCs and the selection of suitable alcohol solvents. Moreover, we successfully fabricated an efficient and stable white light-emitting diode (WLED) with a high luminous efficiency of 23 lm W-1 and CIE color coordinates of (0.3266, 0.3487). Our work provides a new strategy to synthesize Cs3Cu2X5 NCs and holds promise for their potential application in display and lighting devices.

Mineralized aggregates based on native protein phase transition for non-destructive diagnosis of seborrheic skin by surface-enhanced Raman spectroscopy.

The non-homeostasis of sebum secretion by the sebaceous glands in a complicated microenvironment dramatically impacts the skin health of many people in the world. However, the complexity and hydrophobicity of sebum mean a lack of diagnostic tools, which makes it challenging to determine the reason behind cortical imbalances. Herein, a biomimetic mineralized aggregates (PTL@Au and PTB@Au) strategy has been proposed, which could obtain molecular information about sebum by surface-enhanced Raman spectroscopy (SERS). The breaking of disulfide bonds leads to changes in hydrogen bonding, which transform the natural protein into amyloid-like phase transition protein with β-sheets. It provides sites for the nucleation and crystallization of gold nanocrystals to build mineralized aggregates. The mineralized aggregates show robust adhesion stability at the interfaces of different materials through hydrogen bonding and electrostatic interactions. The stabilization, hydrophobicity (contact angle: 134°), and optical transmission (75%) of the structure could result in superior SERS performance for sebum analysis. It should be noted that this enables the sebum detection of clinical samples while ensuring safety. Such generalized bionic mineralization construction and diagnosis methods also serve as an advanced paradigm for a range of biomedical applications.

Superhydrophobic MOF/polymer composite with hierarchical porosity for boosting catalytic performance in an humid environment.

The poor hydrostability of most reported metal-organic frameworks (MOFs) has become a daunting challenge in their practical applications. Recently, MOFs combined with multifunctional polymers can act as a functional platform and exhibit unique catalytic performance; they can not only inherit the outstanding properties of the two components but also offer unique synergistic effects. Herein, an original porous polymer-confined strategy has been developed to prepare a superhydrophobic MOF composite to significantly enhance its moisture or water resistance. The selective nucleation and growth of MOF nanocrystals confined in the pore of PDVB-vim are closely related to the structure-directing and coordination-modulating properties of PDVB-vim. The resultant MOF/PDVB-vim composite not only produces superior superhydrophobicity without significantly disturbing the original features but also exhibits a novel catalytic activity in the Friedel-Crafts alkylation reaction of indoles with trans-β-nitrostyrene because of the accessible sites and synergistic effects.

Stable Perovskite Quantum Dots Light-Emitting Diodes with Efficiency Exceeding 24.

Perovskite nanocrystals for light-emitting diodes are often synthesized by uncontrollable metathesis reactions, suffering from low product yield, nonuniform growth, and poor stability. Herein, by controlling the nucleation kinetics with high dissociation constant (Ka or Kb) acids or bases, homogenous one-route nucleation of perovskite nanocrystals is achieved as the cluster intermediates are eliminated. The stable, shape uniform, and narrow size distribution green nanocrystals are synthesized. The perovskite nanocrystal film exhibites excellent stability in 80% humidity air with only a 10% photoluminescence intensity drop after 16h. Efficient and stable electroluminescence is demonstrated with an FWHM of 16nm at 517nm. The green devices shows a peak EQE of 24.13% with a lifetime T50 of 54min at 10 000cdm-2 .

Nucleation and Growth of Nanocrystals Investigated by In Situ Transmission Electron Microscopy.

Nanocrystals play a key role in the modern energy, catalysis, semiconductor, and biology industries due to their unique structures and performances. However, controllable fabrication of ideal nanocrystals with the desired structures and properties is still challenging, which needs a deep understanding of their nucleation and growth process. Here, the research on nucleation and growth of nanocrystals studied by in situ transmission electron microscopy (TEM) is reviewed, mainly focusing on the atomic migration dynamics, interface evolution, and structure transformation. In addition, the challenges in the study of nanocrystal growth by TEM are discussed and the perspective on the future development of advanced in situ TEM techniques is provided. It is hoped that the review can give a deep insight into the nanocrystal nucleation and growth process, and further contribute to the rational design and precise fabrication of high-performance functional nanocrystals.

Nonclassical mechanisms to irreversibly suppress β-hematin crystal growth

Hematin crystallization is an essential element of heme detoxification of malaria parasites and its inhibition by antimalarial drugs is a common treatment avenue. We demonstrate at biomimetic conditions in vitro irreversible inhibition of hematin crystal growth due to distinct cooperative mechanisms that activate at high crystallization driving forces. The evolution of crystal shape after limited-time exposure to both artemisinin metabolites and quinoline-class antimalarials indicates that crystal growth remains suppressed after the artemisinin metabolites and the drugs are purged from the solution. Treating malaria parasites with the same agents reveals that three- and six-hour inhibitor pulses inhibit parasite growth with efficacy comparable to that of inhibitor exposure during the entire parasite lifetime. Time-resolved in situ atomic force microscopy (AFM), complemented by light scattering, reveals two molecular-level mechanisms of inhibitor action that prevent β-hematin growth recovery. Hematin adducts of artemisinins incite copious nucleation of nonextendable nanocrystals, which incorporate into larger growing crystals, whereas pyronaridine, a quinoline-class drug, promotes step bunches, which evolve to engender abundant dislocations. Both incorporated crystals and dislocations are known to induce lattice strain, which persists and permanently impedes crystal growth. Nucleation, step bunching, and other cooperative behaviors can be amplified or curtailed as means to control crystal sizes, size distributions, aspect ratios, and other properties essential for numerous fields that rely on crystalline materials.

Highly Luminescent Rb-Doped Cs4PbBr6 Nanocrystals in Borogermanate Glass

For the first time, the synthesis, luminescent and structural properties of stable perovskite-type (Cs1−xRbx)4PbBr6 (R = Cs, Rb) nanocrystals are shown. In the absence of rubidium, Cs4PbBr6 and CsPbBr3 perovskite crystals precipitate in the ZnO–Na2O–B2O3–GeO2 glass matrix. With ascending rubidium content, the precipitation of (Cs,Rb)4PbBr6 nanocrystals is replaced by the Rb4PbBr6 nanocrystals nucleation. Nucleated nanocrystals exhibit an intense green luminescence. With an increase of the rubidium content, the luminescence maximum shifts to the blue region, the luminescence quantum yield increases from 28 to 51%, and the average decay time increases from 2 to 8 ns. Several assumptions have been made about the nature of the green luminescence of perovskite-like Cs4PbBr6 and (Cs,Rb)4PbBr6 crystals in glasses. It is concluded that the most probable cause is the impurity inclusions of CsPbBr3 and (Cs,Rb)PbBr3 crystals.

Plasmonic synthesis of Non-homogeneous AuPd alloy for efficient electrocatalyst

Improving electrocatalyst performance is key to the large-scale application of fuel cells. Here, we constructed non-homogeneous AuPd alloy nanoparticles with excellent electrocatalytic activity based on the localized surface plasmon resonance (LSPR) effect of Au nanoparticles for the first time. The mass activity and specific activity of the non-homogeneous AuPd alloy for ethanol oxidation reaction can reach 18.14 A/mgPd and 20.28 mA cm−2, respectively, 10.67 and 3.75 times higher than that of commercial Pd/C. Experimental characterizations and theoretical simulations show that Pd precursor is reduced and deposited on the surface of Au NPs, and the localized temperature field drives the atomic interdiffusion. Finite element simulation results indicate a large temperature gradient around the laser-irradiated Au NPs, and the effective reduction of the Pd precursor is confined to the 2.5 nm thick shell region. This work demonstrates the heterogeneous nucleation and growth of nanocrystals driven by LSPR, providing a promising strategy for the rational design of bimetal nanoparticles.

Affable thermal treatment process to overcome the trade-off relation via interface engineering in an Fe-based amorphous film

As pre-eminent soft magnetic materials, Fe-based amorphous alloys have been extensively studied due to adjustable composition, low cost, and low iron core loss. The soft magnetic properties could be further improved after thermal annealing, which achieve a low coercive force (Hc) due to the low magnetic anisotropy and a high saturation magnetic flux density (Bs) on account of the precipitation of soft magnetic nanocrystalline phases. However, it is a key difficulty to control the nucleation and growth procedures of nanocrystals during annealing, resulting in rapid deterioration of Hc. Here, a soft magnetic Fe76Si8B13Nb3 film with ultra-fine amorphous/crystalline (a/c) core–shell structure is achieved from an amorphous precursor with the nanoscale phase separation. The pre-existing nanoscale phase separation provides vast nucleation sites and interphase boundaries, which could generate high concentration of nanocrystals and depresses the subsequent coarsening behavior even for long-time heat treatment. In consequence, the a/c core–shell soft magnetic film breaks the general trade-off relation in the soft magnetic material family with the highest Bs and lowest Hc simultaneously. This work provides a new perspective to design a/c alloys by amorphous precursor with dual phase structure, and importantly, it supplies effortless thermal treatment requirement to conveniently regulate the microstructures and soft magnetic properties of metallic glasses.