Three-dimensional Crystals Research Articles

Upconverted excitonic photoluminescence from a two-dimensional lead-halide perovskite.

Anti-Stokes photoluminescence (AS-PL) is an interesting optical phenomenon that can cause laser cooling in certain semiconductors where incident laser photons are efficiently converted into photons with higher energy. The underlying upconversion mechanism can be used to realize optical refrigerators, but suited materials need to be developed for actual applications. Here, we investigate the AS-PL properties of a two-dimensional (2D) perovskite PEA2PbI4 single crystal and compare them with those of a three-dimensional (3D) perovskite MAPbI3 single crystal. We find that, in the 2D perovskite PEA2PbI4, which has a large exciton binding energy, the free-exciton PL is dominant and that the measured upconversion gain spectra of both PEA2PbI4 and MAPbI3 crystals are similar. The AS-PL process in these perovskite single crystals is discussed.

Direct imaging of carrier diffusion length in organic-inorganic perovskites

The carrier diffusion length (LD) is of great relevance to the quantum efficiencies of organic-inorganic perovskites. However, so far there is no direct and noncontact measurement of the carrier diffusion length in this emerging material. Herein, we directly visualize the carrier diffusion length of organic-inorganic perovskites via spatial mapping of photoluminescence. Our results reveal that the carrier diffusion length (LD) is 6.25 μm for three-dimensional FAPbBr3 single crystals. Further, we discover that nonlinear and nonradiative effects can be neglectable during the diffusion process of photogenerated carriers in FAPbBr3 single crystals. In contrast, two-dimensional BA2PbI4 single crystals display shorter LD (2.40 μm) due to the transport barrier from their insulating organic layer. Our work simplifies the complicated operation for carrier diffusion length measurements, which is fundamentally important for technical development and scientific research on organic-inorganic perovskites.

X-Ray Crystallographic Structure of Hericium erinaceus Ribonuclease, RNase He1 in Complex with Zinc.

RNase He1 is a guanylic acid-specific ribonuclease of the RNase T1 family from Hericium erinaceus (Japanese name: Yamabushitake). Its RNA degrading activity is strongly inhibited by Zn2+, similar to other T1 family RNases. However, RNase He1 shows little inhibition of human tumor cell proliferation, unlike RNase Po1, another T1 family RNase from Pleurotus ostreatus (Japanese name: Hiratake). Here, we determined the three-dimensional X-ray crystal structure of RNase He1 in complex with Zn, which revealed that Zn binding most likely prevents substrate entry into the active site due to steric hindrance. This could explain why RNase He1 and other T1 family RNases are inhibited by Zn. The X-ray crystal structures revealed that RNase He1 and RNase Po1 are almost identical in their catalytic sites and in the cysteine residues involved in disulfide bonds that increase their stability. However, our comparison of the electrostatic potentials of their molecular surfaces revealed that RNase He1 is negative whereas RNase Po1 is positive; thus, RNase He1 may not be able to electrostatically bind to the plasma membrane, potentially explaining why it does not exhibit antitumor activity. Hence, we suggest that the cationic characteristics of RNase Po1 are critical to the anti-tumor properties of the protein.

Eggshell waste as an eco-friendly and low-cost catalyst for the synthesis of α, β-unsaturated compounds

Three different eggshells, chicken eggshell, duck eggshell and quail eggshell, were used as the catalysts for the Knoevenagel reaction to produce α, β-unsaturated compounds in this work. To obtain the interrelationship among the factors of compositions, structure and catalytic activity, the eggshells were systematically characterized by X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectrophotometry, scanning electron microscopy, and the Hammett indicator method. Eggshells showed the hierarchical and periodic three-dimensional network morphology and calcite crystal phase with the weak alkalinity. All eggshells were active for Knoevenagel reaction, and chicken eggshell showed the highest catalytic activity among them. The reaction conditions were optimized, and the optimal reaction condition was that aromatic aldehyde could efficiently react with active component methylene compound in the presence of 0.5 g chicken eggshell waste in water-ethanol (1:1, volume ratio) at room temperature. Various aromatic aldehydes and active component methylene compounds could be converted into the desired products in high yields, suggesting the high universality of different substrates in the presence of eggshell waste catalyst. In particular, the reaction of 4-cyanobenzaldehyde with malononitrile could be accomplished in 0.7 min with a yield of 99%. Eggshell waste catalysts could be used four times without significant loss in activity, demonstrating their high recyclability and eco-friendliness for the Knoevenagel reaction.

Dimensional hierarchy of higher-order topology in three-dimensional sonic crystals

Wave trapping and manipulation are at the heart of modern integrated photonics and acoustics. Grand challenges emerge on increasing the integration density and reducing the wave leakage/noises due to fabrication imperfections, especially for waveguides and cavities at subwavelength scales. The rising of robust wave dynamics based on topological mechanisms offers possible solutions. Ideally, in a three-dimensional (3D) topological integrated chip, there are coexisting robust two-dimensional (2D) interfaces, one-dimensional (1D) waveguides and zero-dimensional (0D) cavities. Here, we report the experimental discovery of such a dimensional hierarchy of the topologically-protected 2D surface states, 1D hinge states and 0D corner states in a single 3D system. Such an unprecedented phenomenon is triggered by the higher-order topology in simple-cubic sonic crystals and protected by the space group {P}_{mbar{3}m}. Our study opens up a new regime for multidimensional wave trapping and manipulation at subwavelength scales, which may inspire future technology for integrated acoustics and photonics.

Three-dimensional crystals of adaptive knots

Starting with Gauss and Kelvin, knots in fields were postulated to behave like particles, but experimentally they were found only as transient features or required complex boundary conditions to exist and could not self-assemble into three-dimensional crystals. We introduce energetically stable, micrometer-sized knots in helical fields of chiral liquid crystals. While spatially localized and freely diffusing in all directions, they resemble colloidal particles and atoms, self-assembling into crystalline lattices with open and closed structures. These knots are robust and topologically distinct from the host medium, though they can be morphed and reconfigured by weak stimuli under conditions such as those in displays. A combination of energy-minimizing numerical modeling and optical imaging uncovers the internal structure and topology of individual helical field knots and the various hierarchical crystalline organizations that they form.

Preparation and properties of porous P(St-MMA-AA) microsphere anti-glare film

Monodisperse nanoparticles can form two-dimensional or three-dimensional colloidal crystals with periodic ordered structure by self-assembly. They are widely application in optical devices, sensors, electronic devices and drug delivery. Photonic crystals consisting of spherical colloidal particles periodically have various properties and strong designability. Its performance and application have great research value. In order to ensure the transmittance of anti-static, anti-glare and anti-radiation (three-proof) nano-material films, the mist is often not ideal, which limits the practical application of anti-glare films. P(St-MMA-AA) microspheres with different pore sizes were prepared by adjusting the content of acrylic acid. The effects of particle size, concentration and pore structure of microspheres on the transmittance and mist of colloidal crystal coatings were investigated. It was found that increasing the pore structure of microspheres could improve the transmittance of colloidal crystal coatings and keep the mist constant. The experimental results show that the porous colloidal film can reach the standard transmittance when the concentration is 0.01%. It has good anti-glare and acid resistance. The application of porous nanoparticles in high transmittance anti-glare coating is further broadened. This colloidal crystal coating deposits polymer microspheres on the substrate by self-assembly. The preparation method has the advantages of simple equipment, good repeatability, easy operation, non-toxicity and easy synthesis, low cost of raw materials, high yield and environmental friendliness.

Exploring the link between crystal defects and nonaffine displacement fluctuations.

We generalize and then use a recently introduced formalism to study thermal fluctuations of atomic displacements in several two- and three-dimensional crystals. We study both close-packed and open crystals with multiatom bases. Atomic displacement fluctuations in a solid, once coarse grained over some neighborhood, may be decomposed into two mutually orthogonal components. In any dimension d there are always d^{2} affine displacements representing local strains and rotations of the ideal reference configuration. In addition, there exist a number of nonaffine localized displacement modes that cannot be represented as strains or rotations. The number of these modes depends on d and the size of the coarse-graining region. All thermodynamic averages and correlation functions concerning the affine and nonaffine displacements may be computed within harmonic theory. We show that for compact crystals, such as the square and triangular crystals in d=2 and the simple body-centered-cubic and face-centered-cubic crystals in d=3, a single set of d-fold degenerate modes always dominates the nonaffine subspace and is separated from the rest by a large gap. These modes may be identified with specific precursor configurations that lead to lattice defects. In open crystals, such as the honeycomb and kagome lattices, there is no prominent gap, although soft nonaffine modes continue to be associated with known floppy modes representing localized defects. Higher-order coupling between affine and nonaffine components of the displacements quantifies the tendency of the lattice to be destroyed by large homogeneous strains. We show that this coupling is larger by almost an order of magnitude for open lattices as compared to compact ones. Deformation mechanisms such as lattice slips and stacking faults in close-packed crystals can also be understood within this framework. The qualitative features of these conclusions are expected to be independent of the details of the atomic interactions.

Mesoscale Analysis of Homogeneous Dislocation Nucleation

Abstract We perform atomistic simulations of dislocation nucleation in two-dimensional (2D) and three-dimensional (3D) defect-free hexagonal crystals during nanoindentation with circular (2D) or spherical (3D) indenters. The incipient embryo structure in the critical eigenmode of the mesoregions is analyzed to study homogeneous dislocation nucleation. The critical eigenmode or dislocation embryo is found to be localized along a line (or plane in 3D) of atoms with a lateral extent, ξ, at some depth, Y*, below the surface. The lowest energy eigenmode for mesoregions of varying radius, rmeso, centered on the localized region of the critical eigenmode is computed. The energy of the lowest eigenmode, λmeso, decays very rapidly with increasing rmeso and λmeso ≈ 0 for rmeso≳ξ. The analysis of a mesoscale region in the material can reveal the presence of incipient instability even for rmeso≲ξ but gives reasonable estimate for the energy and spatial extent of the critical mode only for rmeso≳ξ. When the mesoregion is not centered at the localized region, we show that the mesoregion should contain a critical part of the embryo (and not only the center of embryo) to reveal instability. This scenario indicates that homogeneous dislocation nucleation is a quasilocal phenomenon. Also, the critical eigenmode for the mesoscale region reveals instability much sooner than the full system eigenmode. We use mesoscale analysis to verify the scaling laws shown previously by Garg and Maloney in 2D [2016, “Universal Scaling Laws for Homogeneous Dissociation Nucleation During Nano-Indentation,” J. Mech. Phys. Solids, 95, pp. 742–754.] for the size, ξ, and depth from the surface, Y*, of the dislocation embryo with respect to indenter radius, R, in full 3D simulations.

Mechanism of surface passivation of methylammonium lead tribromide single crystals by benzylamine

Hybrid organic-inorganic perovskites are semiconductors that have great potential for optoelectronic applications such as light-emitting diodes, photodetectors, and solar cells. In such devices, the surface plays a crucial role in the performance and stability, as it strongly influences the recombination rate of excited charge carriers. It is reported that molecular ligands such as benzylamine are capable of reducing the surface trap state density in thin films. In this work, we aim to clarify the mechanisms that govern the surface passivation of hybrid perovskites by benzylamine. We developed a versatile approach to investigate the influence of benzylamine passivation on the well-defined surface of freshly cleaved hybrid perovskite crystals. We show that benzylamine permanently passivates surface trap states in these single crystals, resulting in enhanced photoluminescence and charge carrier lifetimes. Additionally, we show that exposure to benzylamine leads to the replacement of the methylammonium cations by benzylammonium, thereby creating a thermodynamically more stable two-dimensional (2D) perovskite (BA)2PbBr4 on the surface of the three-dimensional crystal. This conversion to a 2D perovskite drives an anisotropic etching of the crystal surface, with the {100} planes being most prone to etching. Initially, square etching pits appear spread over the surface. As time elapses, these etching pits broaden and merge to yield large flat terraces that are oriented normally to the cleaving plane when they form. A thorough understanding of the mechanisms governing the surface passivation is crucially important to optimize and design novel passivation schemes, with the ultimate goal of further advancing the efficiency of optoelectronic devices based on hybrid perovskites.

Highly Selective Rh(III) Recovery from HCl Solutions Using Aromatic Primary Diamines via Formation of Three-Dimensional Ionic Crystals.

A new Rh(III) separation method using metal-containing hydrochloric acid (HCl) solutions has been developed. This method includes Rh(III) precipitation with high selectivity using aromatic primary diamines as precipitants. The compound p-phenylene diamine dihydrochloride (PPDA) successfully precipitates only Rh(III) from HCl solutions containing Pd(II), Pt(IV), and Rh(III). Furthermore, highly selective Rh(III) recovery from the simulated spent catalyst leach solution, comprising Pd, Pt, Rh, Ce, Al, Ba, Zr, La, and Y in 5 M HCl, was achieved using PPDA. Single-crystal X-ray analysis revealed that the Rh(III)-containing precipitate using PPDA forms three-dimensional ionic crystals comprising the [RhCl6]3–/ammonium form of PPDA/chloride anion/H2O at a 1:2:1:2 ratio. Formation of these unique ionic crystals plays a key role in the highly selective Rh(III) recovery. This Rh(III) recovery method will be promising for use in the purification process of Rh as well as the practical Rh recovery from spent catalysts.

Achieving Small Exciton Binding Energies in Small Molecule Acceptors for Organic Solar Cells: Effect of Molecular Packing.

Because of strong exciton binding energy (Eb), an exciton dissociation process and extra energy losses are present in organic solar cells relative to inorganic and perovskite solar cells. Here, we calculated the Eb of a series of small molecule acceptors in solid crystals by a self-consistent quantum mechanics/embedded charge approach. The results show that the Eb values are substantially reduced from the gas phase to solid state because of electronic polarization (mainly from the induction effect of charges). Moreover, in contrast to little changes in the gas phase, the Eb in the solid state can vary significantly, indicating an important molecular packing effect. Remarkably, an extremely weak Eb of 0.04 eV is achieved in a three-dimensional packing crystal, which is comparable to the Eb of organo-lead trihalide perovskites. This work underlines the importance of three-dimensional molecular packing for achieving small Eb and will be helpful in reducing energy losses in organic solar cells.

Inelastic scattering and solvent scattering reduce dynamical diffraction in biological crystals.

Multi-slice simulations of electron diffraction by three-dimensional protein crystals have indicated that structure solution would be severely impeded by dynamical diffraction, especially when crystals are more than a few unit cells thick. In practice, however, dynamical diffraction turned out to be less of a problem than anticipated on the basis of these simulations. Here it is shown that two scattering phenomena, which are usually omitted from multi-slice simulations, reduce the dynamical effect: solvent scattering reduces the phase differences within the exit beam and inelastic scattering followed by elastic scattering results in diffusion of dynamical scattering out of Bragg peaks. Thus, these independent phenomena provide potential reasons for the apparent discrepancy between theory and practice in protein electron crystallography.

Structure of a self-assembled three-dimensional DNA crystal framework for the precise organization of biomaterials

Structure of a self-assembled three-dimensional DNA crystal framework for the precise organization of biomaterials

Two-Dimensional Nonclose-Packed Colloidal Crystals by the Electrostatic Adsorption of Three-Dimensional Charged Colloidal Crystals.

We demonstrate that nonclose-packed two-dimensional (2D) colloidal crystals fixed on flat solid surfaces can be obtained by the electrostatic adsorption of three-dimensional (3D) charged colloidal crystals onto oppositely charged substrates. 3D colloidal crystals of negatively charged polystyrene (diameter d = 500 nm) and silica (d = 510 and 550 nm) particles were formed in their aqueous dispersions. Then, a single layer of the 3D crystals (the particle volume fraction = ∼0.07-0.3) was adsorbed onto a glass surface, which was earlier modified with 3-aminopropyltriethoxysilane (APTES), a cationic silane coupling reagent. Under salt-free conditions, the lowermost layer of the 3D crystals, which was oriented parallel to the substrate, was adsorbed onto the substrate surface, forming 2D crystals. Centimeter-sized, large 2D silica crystals were produced by combining a unidirectional 3D crystallization of the silica colloid under a base concentration gradient and a unidirectional adsorption under an acidic concentration gradient, which allowed tuning of the charge number on the APTES-modified substrate. The interparticle separations of the resulted 2D crystals did not vary greatly (within 5%) over a large area (length: 2 cm); however, the separations were smaller than the initial value because of gravitational sedimentation. We also produced 2D crystals of gold particles (d = 250 nm), which we expect to be applicable as plasmonic materials. The present study will provide a facile strategy to produce nonclose-packed 2D colloidal crystals of various types of particles, including large and high-density particles.

From Cubes to Dice: Solvent-Regulated Morphology Engineering of Endohedral Fullerene Microcrystals with Anomalous Photoluminescence Enhancement.

Despite recent successes in preparing three-dimensional crystals of empty fullerenes, such as C60 and C70 , 3D endohedral fullerene crystals, and especially hollow nanostructures, have been scarcely reported. A universal approach has now been developed to prepare shape-tunable 3D crystals of several metal nitride clusterfullerenes, including cubes and dice (hollow cubes with holes at the center of each face), which can be readily switched by changing the volume ratio of good (mesitylene) and poor (isopropanol) solvents. Synchrotron-based soft X-ray nano-computed tomography was used to unambiguously identify the interior microstructure of the dice-shaped crystals of Tb3 N@C80 , and especially the depth of the hole at each face, confirming that the dice has a solid center and the holes are not interconnected. Owing to the enhanced light absorption, the dice-shaped crystals exhibit enhanced photoluminescence relative to that of the cubes.

Three dimensional metallic porous SiC4 allotropes: Stability and battery applications

Three metallic three-dimensional (3D) microporous SiC4 crystals are identified for the first time by using an unbiased structure search based on the particle-swarm optimization (PSO) algorithm combined with density functional theory (DFT) calculations, which are found to be thermally, dynamically and mechanically stable. The unusual metallicity of these three microporous SiC4 allotropes stems from the delocalized p electrons along carbon ribbons or chains. Moreover, empowered by the appropriate channel size and metallic feature, SiC4-Ⅰ manifests as a promising anode material for Na-ion batteries with theoretical capacity of 176.3 mAhg−1, diffusion energy barrier of 0.25–0.41 eV for Na ions, appropriate average open circuit voltage of 0.55 V and negligible volume change of 0.57% during charging/discharging process.

Designing Higher Resolution Self-Assembled 3D DNA Crystals via Strand Terminus Modifications.

DNA tensegrity triangles self-assemble into rhombohedral three-dimensional crystals via sticky ended cohesion. Crystals containing two-nucleotide (nt) sticky ends (GA:TC) have been reported previously, and those crystals diffracted to 4.9 Å at beamline NSLS-I-X25. Here, we analyze the effect of varying sticky end lengths and sequences as well as the impact of 5'- and 3'-phosphates on crystal formation and resolution. Tensegrity triangle motifs having 1-, 2-, 3-, and 4-nt sticky ends all form crystals. X-ray diffraction data from the same beamline reveal that the crystal resolution for a 1-nt sticky end (G:C) and a 3-nt sticky end (GAT:ATC) were 3.4 and 4.2 Å, respectively. Resolutions were determined from complete data sets in each case. We also conducted trials that examined every possible combination of 1-nucleotide and 2-nucleotide sticky-ended phosphorylated strands and successfully crystallized all 16 possible combinations of strands. We observed the position of the 5'-phosphate on either the crossover (1), helical (2), or central strand (3) affected the resolution of the self-assembled crystals for the 2-turn monomer (3.0 Å for 1-2P-3P) and 2-turn dimer sticky ended (4.1 Å for 1-2-3P) systems. We have also examined the impact of the identity of the base flanking the sticky ends as well as the use of 3'-phosphate. We conclude that crystal resolution is not a simple consequence of the thermodynamics of the direct nucleotide pairing interactions involved in molecular cohesion in this system.

Protein Materials Engineering with DNA.

Proteins are a class of nanoscale building block with remarkable chemical complexity and sophistication: their diverse functions, shapes, and symmetry as well as atomically monodisperse structures far surpass the range of conventional nanoparticles that can be accessed synthetically. The chemical topologies of proteins that drive their assembly into materials are central to their functions in nature. However, despite the importance of protein materials in biology, efforts to harness these building blocks synthetically to engineer new materials have been impeded by the chemical complexity of protein surfaces, making it difficult to reliably design protein building blocks that can be robustly transformed into targeted materials. Here we describe our work aimed at exploiting a simple but important concept: if one could exchange complex protein-protein interactions with well-defined and programmable DNA-DNA interactions, one could control the assembly of proteins into structurally well-defined oligomeric and polymeric materials and three-dimensional crystals. As a class of nanoscale building block, proteins with surface DNA modifications have a vast design space that exceeds what is practically and conceptually possible with their inorganic counterparts: the sequences of the DNA and protein and the chemical nature and position of DNA attachment all play roles in dictating the assembly behavior of protein-DNA conjugates. We summarize how each of these design parameters can influence structural outcome, beginning with proteins with a single surface DNA modification, where energy barriers between protein monomers can be tuned through the sequence and secondary structure of the oligonucleotide. We then explore challenges and progress in designing directional interactions and valency on protein surfaces. The directional binding properties of protein-DNA conjugates are ultimately imposed by the amino acid sequence of the protein, which defines the spatial distribution of DNA modification sites on the protein. Through careful design and mutagenesis, bivalent building blocks that bind directionally to form one-dimensional assemblies can be realized. Finally, we discuss the assembly of proteins densely modified with DNA into crystalline superlattices. At first glance, these protein building blocks display crystallization behavior remarkably similar to that of their DNA-functionalized inorganic nanoparticle counterparts, which allows design principles elucidated for DNA-guided nanoparticle crystallization to be used as predictive tools in determining structural outcomes in protein systems. Proteins additionally offer design handles that nanoparticles do not: unlike nanoparticles, the number and spatial distribution of DNA can be controlled through the protein sequence and DNA modification chemistry. Changing the spatial distributions of DNA can drive otherwise identical proteins down distinct crystallization pathways and yield building blocks with exotic distributions of DNA that crystallize into structures that are not yet attainable using isotropically functionalized particles. We highlight challenges in accessing other classes of architectures and establishing general design rules for DNA-mediated protein assembly. Harnessing surface DNA modifications to build protein materials creates many opportunities to realize new architectures and answer fundamental questions about DNA-modified nanostructures in both materials and biological contexts. Proteins with surface DNA modifications are a powerful class of nanomaterial building blocks for which the DNA and protein sequences and the nature of their conjugation dictate the material structure.

Sensitive biological detection based on Langmuir–Blodgett films prepared fromdiluted silica suspensions

Self-assembled three-dimensional (3-D) colloidal crystals have been extensively utilized in nanolithography for fabricating a wide spectrum of functional periodic nanostructures for important technological applications. Here a simple and versatile way is reported using silica colloids to prepare close-packed particle multilayers by the Langmuir– Blodgett technique to create highly ordered 3-D colloidal crystals with unusual nanoarrays on a large variety of substrates. Successive deposition of monolayers using amphiphilic molecules in this approach allows control of the layer thickness, particle size, and especially packing structure of them in each layer. It has been demonstrated that the Langmuir–Blodgett film’s transparency and high antiglare optical properties are preserved even after multiple colloidal particle transfers on both straight and curved surfaces. The surface prepared by the Langmuir–Blodgett technique shows remarkable sensitivity for potential biodetection applications. These colloidal templated films have an optical response time of less than 40 s against essential bioproduct vapors. It is shown that the results are consistent with the Kelvin equation (ln P/Po = 􀀀2 Vl /rRT) when the liquid water layer is getting thicker.