Selective Nucleation Research Articles

Controllable lithium nucleation within longitudinally bent carbon nanoribbons for stable lithium metal anodes

Though lithium metal has long been regarded as an ideal anode material for high-density batteries, the potential safety hazards greatly hampered its applications due to the non-uniform lithium nucleation and subsequent uncontrollable growth of lithium dendrites. To address these problems, herein, we developed carbon nanoribbons (LBCRs) with linearly distributed nucleation seeds and longitudinally bent structure. In the unique LBCRs, not only nucleation seeds located along edges decreased the nucleation barrier of lithium, inducing selective lithium nucleation, but also conductive carbon skeleton with bent structure regulated Li ion flux, preventing the formation of lithium dendrites. Moreover, LBCRs alleviated the volume change during cycling by guiding the lithium deposition inside the cavity. On the consequence, controllable lithium deposition was realized within LBCRs, and resulted composite anodes exhibited superior cycling stability including a low voltage hysteresis of 47.4 mV with a long cycle life over 700 h and a stable Coulombic efficiency above 94%.

Recyclable Graphene Sheets as a Growth Template for Crystalline ZnO Nanowires.

Recent advances in nanoscience have opened ways of recycling substrates for nanomaterial growth. Novel materials, such as atomically thin materials, are highly desirable for the recycling substrates. In this work, we report recycling of monolayer graphene as a growth template for synthesis of single crystalline ZnO nanowires. Selective nucleation of ZnO nanowires on graphene was elucidated by scanning electron microscopy and density functional theory calculation. Growth and subsequent separation of ZnO nanowires was repeated up to seven times on the same monolayer graphene film. Raman analyses were also performed to investigate the quality of graphene structure along the recycling processes. The chemical robustness of graphene enables the repetitive ZnO nanowire growth without noticeable degradation of the graphene quality. This work presents a route for graphene as a multifunctional growth template for diverse nanomaterials such as nanocrystals, aligned nanowires, other two-dimensional materials, and semiconductor thin films.

Ultrasound-assisted theophylline polymorphic transformation: Selective polymorph nucleation, molecular mechanism and kinetics analysis

In this paper, the ultrasound-assisted solvent-mediated polymorphic transformation of theophylline was explored in detail. The induction time and reconstruction time were significantly decreased by ultrasound, thereby decreasing the total transformation time and promoting the transformation process. The ultrasound-promoted efficiency of nucleation was different in three alcoholic solvents, which was difficult to explain by traditional kinetic effects. To resolve the above confusion, binding energies calculated by Density Functional Theory were applied to explore the relationship between the ultrasound-promoted efficiency of nucleation and solute–solvent interactions. Then, a possible molecular self-assembly nucleation pathway affected by ultrasound was proposed: the ultrasound could change and magnify the crucial effect of the specific sites of solute–solvent interactions in the nucleation process. Finally, the transformation kinetics with different effective ultrasonic energies was quantitatively analyzed by Avrami-Erofeev model, indicating that the dissolution element in the rate-limiting step was gradually eliminated by higher ultrasonic energy. Fortunately, the elusive crystal form V could be easily obtained by the ultrasound-assisted polymorph transformation. This proved to be a robust method to produce high purity form V of theophylline. The outcome of this study demonstrated that the proper ultrasonic irradiation had the potential to produce specific polymorphs selectively.

Dynamic Light Scattering Study of a Laser-Induced Phase-Separated Droplet of Aqueous Glycine.

Tightly focusing a continuous-wave, near-infrared laser beam at the air/solution interface of a millimeter-thick layer of glycine in D2O forms a crystal through a polymorphically and spatially controlled nucleation process known as gradient-force laser-induced nucleation or optical-tweezer laser-induced nucleation. However, when this same beam is focused at the glass/solution interface of a film of aqueous glycine, a highly concentrated laser-induced phase-separated (LIPS) solution droplet is formed that does not nucleate while the focusing beam remains on. Two competing theories have emerged about the nature of the LIPS droplet: one proposes that it is a merger of prenucleation metastable nanodroplets and clusters into one large homogeneous "dense liquid droplet", and the other stipulates that it is the result of the partitioning of larger droplets into the new phase, but not a merging of droplets, around the focal point of the beam. In order to determine the nature of the LIPS droplet, dynamic light scattering was used to detect the presence of nanodroplets undergoing Brownian motion within the droplet and to measure their relative size following a range of laser exposure times. The observation of nanodroplets in motion in the center of the LIPS droplet revealed that the application of optical tweezers at the glass/solution interface forms a relatively monodisperse collection of large nanodroplets (>700 nm) concentrated around the focal point of the beam with smaller particles (<100 nm) depleted within the first 2 min of laser exposure. The LIPS droplet quickly reaches a steady state and is not affected by increasing focusing times. These findings allow for a better understanding of the interactions of optical tweezers with aqueous glycine nanodroplets. This understanding will help in studying the fundamental nature of metastable nanodroplets. More practically, laser-induced phase separation makes possible the nucleation-free separation of large nanodroplets from small clusters, facilitating materials technologies such as high purity, polymorphically selective nucleation of crystals and co-crystals used for pharmaceuticals, dyes, and photovoltaics.

The growth of a multi-principal element (CoCrFeMnNi) oxynitride film by direct current magnetron sputtering using air as reactive gas

CoCrFeMnNi multi-principal element alloy films were grown by direct current magnetron sputtering in a mixture of argon and air. The air fraction was varied from 4 to 50%, which resulted in a change of the phase state of the growing film. A 〈100〉 preferred orientation face centered cubic metal (doped with O and N) structure develops below 12% of air. Between 12 and 30% air, a two phase 〈100〉 preferred orientation face centered cubic metal + oxynitride (B1) structure forms. Above 30% of air a single phase B1 oxynitride structure is observed. Compared to nitrogen, oxygen is preferentially incorporated into the growing structures. The 〈100〉 preferential orientation is the result of selective nucleation (below 30% of air) or competing growth (above 30% of air) of the forming crystals.Detailed microscopic analysis shows a complex structure for both the metal and the oxynitride phase in the films deposited at low and high air fraction. In both cases, the films are characterized by local structures ordered on a few nanometer scale and their formation is explained as a result of spinodal decomposition of the as-formed homogenous structure which occurs during film growth.

Selective nucleation and targeted deposition effect of lithium in a lithium-metal host anode

In this work, we report an interesting selective nucleation and targeted deposition effect of lithium in F-enriched macropores of carbon nanofibers.

Spatially Controlled Lithium Deposition on Silver‐Nanocrystals‐Decorated TiO2 Nanotube Arrays Enabling Ultrastable Lithium Metal Anode

Abstract3D scaffolds and heterogeneous seeds are two effective ways to guide Li deposition and suppress Li dendrite growth. Herein, 3D TiO2 nanotube (TNT) arrays decorated using ultrafine silver nanocrystals (7–10 nm) through cathodic reduction deposition are first demonstrated as a confined space host for lithium metal deposition. First, TiO2 possesses intrinsic lithium affinity with large Li absorption energy, which facilitates Li capture. Then, ultrafine silver nanocrystals decoration allows the uniform and selective nucleation in nanoscale without a nucleation barrier, leading to the extraordinary formation of lithium metal importing into 3D nanotube arrays. As a result, Li metal anode deposited on such a binary architecture (TNT‐Ag‐Li) delivers a high Coulomb efficiency at around 99.4% even after 300 cycles with a capacity of 2 mA h cm−2. Remarkably, TNT‐Ag‐Li exhibits ultralow overpotential of 4 mV and long‐term cycling life over 2500 h with a capacity of 2 mAh cm–2 in Li symmetric cells. Moreover, the full battery with 3D spaced Li nanotubes anode and LiFeO4 cathode exhibits a stable and high capacity of 115 mA h g–1 at 5 C and an excellent Coulombic efficiency of ≈100% over 500 cycles.

Resolving the Atomic Structure of Sequential Infiltration Synthesis Derived Inorganic Clusters.

Sequential infiltration synthesis (SIS) is a route to the precision deposition of inorganic solids in analogy to atomic layer deposition but occurs within (vs upon) a soft material template. SIS has enabled exquisite nanoscale morphological complexity in various oxides through selective nucleation in block copolymers templates. However, the earliest stages of SIS growth remain unresolved, including the atomic structure of nuclei and the evolution of local coordination environments, before and after polymer template removal. We employed In K-edge extended X-ray absorption fine structure and atomic pair distribution function analysis of high-energy X-ray scattering to unravel (1) the structural evolution of InOxHy clusters inside a poly(methyl methacrylate) (PMMA) host matrix and (2) the formation of porous In2O3 solids (obtained after annealing) as a function of SIS cycle number. Early SIS cycles result in InOxHy cluster growth with high aspect ratio, followed by the formation of a three-dimensional network with additional SIS cycles. That the atomic structures of the InOxHy clusters can be modeled as multinuclear clusters with bonding patterns related to those in In2O3 and In(OH)3 crystal structures suggests that SIS may be an efficient route to 3D arrays of discrete-atom-number clusters. Annealing the mixed inorganic/polymer films in air removes the PMMA template and consolidates the as-grown clusters into cubic In2O3 nanocrystals with structural details that also depend on SIS cycle number.

A molecular dynamics study of epitaxy-induced chain orientation and ordering of isotactic polypropylene

Phase selective nucleation of single chain isotactic polypropylene (iPP) into specific crystalline polymorphs is enabled by heterogeneous nucleating agents. Molecular dynamics simulations were used to investigate the ordering of isolated iPP chains over ideal (α-iPP and β-iPP) and commercial (triphenodithiazine, TPDT) heterogeneous nucleating surfaces during the early stages of nucleation. The ordering of an iPP chain during nucleation is analyzed by following the evolution of helix conformations, chiral order parameter, chain orientation and radius of gyration. The results show that α-iPP and β-iPP have a greater tendency to select chirality. However, TPDT is the most efficient in orienting the chain because of bulky phenyl groups on its surface. Based on helix evolution and segment orientation, early-stage ordering of iPP on crystalline surfaces is proposed to proceed by two different routes; (i) CTEH (coil-to-extended helix) where helix formation and segment orientation occur simultaneously, and (ii) CTEC (coil-to-extended coil) where segment orientation occurs without helix formation, thus indicating multistage nucleation through an intermediate mesomorphic phase. Whereas, CTEC is the predominant ordering route on TPDT, both CTEC and CTEH occur simultaneously on α-iPP and β-iPP, emphasizing the important role of epitaxy in early-stage ordering during crystallization.

Zeolite LTA structure generation by Coordination Sequence and Vertex Symbol

Abstract A graph theory based computational program CVdecoder is proposed that enable us to construct a zeolite LTA structure topology from Coordination Sequence and Vertex Symbol information. During the generation process, a critical size of cluster (graph) denoting as “Minimal Fingerprint Structure (MFS)” is found. The generation process after the MFS formation is no longer requiring more topological information but vertex transitive. The cluster is also smallest characteristic cluster that could only be found in LTA, that may provide a useful view of zeolite polymorph selective nucleation.

3D Vertically Aligned Li Metal Anodes with Ultrahigh Cycling Currents and Capacities of 10 mA cm−2/20 mAh cm−2 Realized by Selective Nucleation within Microchannel Walls

AbstractAlthough metallic lithium is regarded as the “Holy Grail” for next‐generation rechargeable batteries due to its high theoretical capacity and low overpotential, the uncontrollable Li dendrite growth, especially under high current densities and deep plating/striping, has inhibited its practical application. Herein, a 3D‐printed, vertically aligned Li anode (3DP‐VALi) is shown to efficiently guide Li deposition via a “nucleation within microchannel walls” process, enabling a high‐performance, dendrite‐free Li anode. Moreover, the microchannels within the microwalls are beneficial for promoting fast Li+ diffusion, supplying large space for the accommodation of Li during the plating/stripping process. The high‐surface‐area 3D anode design enables high operating current densities and high areal capacities. As a result, the Li–Li symmetric cells using 3DP‐VALi demonstrate excellent electrochemical performances as high as 10 mA cm−2/10 mAh cm−2 for 1500 h and 5 mA cm−2/20 mAh cm−2 for 400 h, respectively. Additionally, the Li–S and Li–LiFePO4 cells using 3DP‐VALi anodes present excellent cycling stability up to 250 and 800 cycles at a rate of 1 C, respectively. It is believed that these new findings could open a new window for dendrite‐free metal anode design and pave the way toward energy storage devices with high energy/power density.

Nanobubbles heterogeneous nucleation induced by temperature rise and its influence on minerals flotation

The application of nanobubbles (NBs) in mineral flotation has been widely explored in the last decade, while much few researches have been done on revealing the heterogeneous nucleation of NBs on mineral particles. In this study, the heterogeneous nucleation of NBs induced by temperature rise on dodecylamine-modified muscovite surfaces and its influences on the associated minerals flotation were investigated. Results of special topography and force curve of NBs suggest that NBs can hardly nucleate on the hydrophilic muscovite surface, while they can appear on the hydrophobized mineral surfaces. Furthermore, NBs nucleation on the hydrophobized muscovite surfaces enhances the attraction between mineral particles, resulting in more significant particles aggregation and better flotation performances. The selective nucleation of NBs on more hydrophobic surfaces also contributes to higher separation efficiency, based on the flotation index of actual muscovite ores.

Selective nucleation of ice crystals depending on the inclination angle of nanostructures.

Heterogeneous nucleation is decided by many factors, and surface morphology is one of the most important elements. This paper reports the selective ice nucleation and growth process on a series of nanorods with different inclinations, which were rarely mentioned in previous research studies. It is found that the nanorods with special inclinations can cause the selective nucleation of ice crystals because of the spatial geometry matching. On this basis, we can regulate the ice crystal types (mainly including cubic ice and hexagonal ice) accordingly and even improve the freezing efficiency via controlling the inclinations of surface nanorods. In particular, cubic ice occupies the dominant role in the ice crystal on the surface of 45°-inclination nanorods, yet 90°-inclination nanorods are more beneficial for the formation of hexagonal ice. The shape of the nanorods not only controls the type of ice crystal, but also changes the freezing efficiency because different ice crystals have an unequal nucleation energy barrier. There are no apparent differences in the freezing efficiency on nanostructures with 45°, 75° and 90° inclination nanorods, and 60°-inclination nanorods are more favorable for ice nucleation. Our studies can promote the understanding on the selective nucleation of ice crystals and provide a theoretical basis for achieving the regulation of freezing efficiency.

Transferable GaN Enabled by Selective Nucleation of AlN on Graphene for High‐Brightness Violet Light‐Emitting Diodes

AbstractA transferable GaN epilayer is grown on an improved aluminum nitride (AlN)/graphene composite substrate. In this study, theoretical calculations using first‐principles calculations based on density functional theory are carefully conducted to further examine the formation mechanism of AlN on graphene. AlN selectively grows on graphene via its optimal nucleation site, which leads to the selective nucleation of AlN on graphene via quasi‐van der Waals epitaxy. Thus, an AlN composite nucleation layer is innovatively inserted between graphene and GaN, using the time‐distributed and constant‐pressure growth method by metal organic chemical vapor deposition. Moreover, a high‐quality GaN epilayer can be grown while ensuring the successful exfoliation of GaN by overcoming weak van der Waals forces between the graphene and the epilayer. The as‐fabricated violet light‐emitting diodes (LEDs) deliver an ultrahigh light output power. This method demonstrates the possibility of achieving a high‐quality vertical structure for LEDs and the ability to mechanically transfer to achieve flexible lighting.

Ballistic InSb Nanowires and Networks via Metal-Sown Selective Area Growth.

Selective area growth is a promising technique to realize semiconductor-superconductor hybrid nanowire networks, potentially hosting topologically protected Majorana-based qubits. In some cases, however, such as the molecular beam epitaxy of InSb on InP or GaAs substrates, nucleation and selective growth conditions do not necessarily overlap. To overcome this challenge, we propose a metal-sown selective area growth (MS SAG) technique, which allows decoupling selective deposition and nucleation growth conditions by temporarily isolating these stages. It consists of three steps: (i) selective deposition of In droplets only inside the mask openings at relatively high temperatures favoring selectivity, (ii) nucleation of InSb under Sb flux from In droplets, which act as a reservoir of group III adatoms, done at relatively low temperatures, favoring nucleation of InSb, and (iii) homoepitaxy of InSb on top of the formed nucleation layer under a simultaneous supply of In and Sb fluxes at conditions favoring selectivity and high crystal quality. We demonstrate that complex InSb nanowire networks of high crystal and electrical quality can be achieved this way. We extract mobility values of 10 000-25 000 cm2 V-1 s-1 consistently from field-effect and Hall mobility measurements across single nanowire segments as well as wires with junctions. Moreover, we demonstrate ballistic transport in a 440 nm long channel in a single nanowire under a magnetic field below 1 T. We also extract a phase-coherent length of ∼8 μm at 50 mK in mesoscopic rings.

Critical Size of Secondary Nuclei Determined via Nucleation Theorem Reveals Selective Nucleation in Three-Component Co-Crystals

The critical size of the secondary nuclei plays an important role in determining the crystal growth rate. In the past, the Nucleation Theorem has been applied to determine the number of molecules in the critical nuclei of a single-component crystal via variation of the crystal growth rate with dilution by the non-crystallizable component. In this work, we extend the method to the three-component co-crystal poly (ethylene oxide)/urea/thiourea inclusion compound. The theoretical crystal growth kinetics were deduced and the dependence of the radial growth rate of the inclusion compound spherulites on the mass fraction of urea in urea/thiourea was measured. The results reveal that the secondary nuclei of the poly (ethylene oxide)/urea/thiourea inclusion compound consist mainly of ethylene oxide repeating units and urea molecules. We propose that only urea molecules and ethylene oxide repeating units are selected to form the secondary nuclei while co-crystallization of the three components happens at the lateral spreading stage. As a result, the composition of the critical secondary nuclei is different from that of the bulk inclusion compound crystals. The work is expected to deepen our understanding of the nucleation of multi-component co-crystals.

Hierarchical manganese sillenite Bi12MnO20 microparticles assembled by nanocubes with microwave absorption enhancement

Pure manganese sillenite (Bi12MnO20) microparticles with average sizes of 11.5–16.8 μm were prepared via an oxidation-precipitation method assisted by microwave-heating. Their microstructures are characterized by the shapes of single or multiple intersecting tetrahedrons and the massive nanocubes in ordered arrays on each tetrahedron surface. Such hierarchical Bi12MnO20 microparticles have not been reported so far, while their growth mechanisms may include the formation of active centers, the selective nucleation on active center surfaces and the growth of nanocubes along certain orientations. In electromagnetic determination, noticeable resonances both in permittivity and permeability were revealed beyond relaxations. A cone-like reflection loss peak was obtained with the minimum value of −39.1 dB and a broad effective microwave absorption bandwidth covering 12.7–14.6 GHz. Moreover, the reflection loss peak stagnates at the same frequency regardless of the absorbent thickness variations, suggesting a high performance in microwave attenuation.

Preparation of polymeric foams with bimodal cell size: An application of heterogeneous nucleation effect of nanofillers

A new method was proposed for fabricating the polymer foams with bimodal structure. Briefly, nanoparticles and polymer powders were dry-mixed by ball-milling and then hot-pressed into the composites in which nanoparticles were selectively distributed at the interfaces between polymer multi-facets. Upon batch foaming using scCO2 as blowing agent, bimodal structure was generated due to the selective distribution and heterogeneous nucleation effect of the nanoparticles. Using this method, several bimodal composite foams based on different nanoparticles, i.e. graphene, carbon nanotubes, and silica nanoparticles and different polymers, i.e. thermoplastic polyurethane (TPU) and polystyrene (PS) were successfully fabricated. Specifically, TPU/graphene system was systemically studied. The results showed that the foam morphologies could be easily tuned by changing nanoparticle content, particle size of polymer powder, hot-pressing temperature and pressure, as well as foaming conditions (e. g. foaming temperature and pressure), indicating the great simplicity and tune-ability of this method.

The use of biocompatible crystalline substrates for the heterogeneous nucleation and polymorphic selection of indomethacin

A heteroepitaxial nucleation approach was used to control the phase selective nucleation of indomethacin using biocompatible, organic crystalline substrates.

Crystallization of Methylammonium Lead Halide Perovskites by Optical Trapping.

Single crystals of organolead halide perovskites attract much attention to electrooptical and photovoltaic applications. They are usually prepared in precursor solutions incubated at controlled temperatures or under optimized vapor atmosphere conditions, and thus, multiple perovskite crystals are nucleated all over the solution. Multiple nucleation of crystals prevents efficient use of precursors in the preferential growth of large single crystals. An innovative approach is presented for spatiotemporally controlled, selective nucleation and growth of single crystals of lead halide perovskites by optical trapping with a focused laser beam. Upon such trapping in unsaturated precursor solutions, nucleation of MAPbX3 (MA=CH3 NH3 + ; X=Cl- , Br- , or I- ) is induced at the focal spot through increase in the concentration of perovskite precursors in the focal volume. The rate at which the nucleated crystal grows depends upon whether the perovskite absorbs the trapping laser or not. These findings suggest that optical trapping would be useful to prepare various perovskite single crystals and modify their optical and electronic properties; thereby, offering new methods for engineering of perovskite crystals.