We develop a model for the excitation of erbium ions in erbium-doped silicon nanocrystals via coupling from confined excitons generated within the silicon nanoclusters. The model provides a phenomenological picture of the exchange mechanism and allows us to evaluate an effective absorption cross section for erbium of up to 7.3ϫ10 Ϫ17 cm 2 : four orders of magnitude higher than in stoichiometric silica. We address the origin of the 1.6 eV emission band associated with the silicon nanoclusters and determine absorption cross sections and excitonic lifetimes for nanoclusters in silica which are of the order of 1.02ϫ10 Ϫ16 cm 2 and 20-100 s, respectively.

InGaN multiple-quantum-well structures grown by metal–organic chemical-vapor deposition on GaN and capped by p-type GaN are found to contain inverted pyramids of indium-free GaN. High-resolution structural and chemical analyses of these “V-defects” by a number of complementary transmission electron microscopy techniques show that the InGaN quantum wells end abruptly at the V-defect interfaces, which lie on {10–11} planes. Each V-defect has at its center a threading edge dislocation, indicating that the defects are initiated at edge dislocation cores in the presence of indium. The lower temperatures of InGaN/GaN quantum-well growth (790 °C/950 °C) assist the formation of V-pits, which are subsequently filled in during the growth at higher temperature (1045 °C) of the p-type capping layer.

Glioblastoma (GBM) is one of the most difficult cancers to effectively treat, in part because of the lack of precision therapies and limited therapeutic access to intracranial tumor sites due to the presence of the blood-brain and blood-tumor barriers. We have developed a precision medicine approach for GBM treatment that involves the use of brain-penetrant RNA interference–based spherical nucleic acids (SNAs), which consist of gold nanoparticle cores covalently conjugated with radially oriented and densely packed small interfering RNA (siRNA) oligonucleotides. On the basis of previous preclinical evaluation, we conducted toxicology and toxicokinetic studies in nonhuman primates and a single-arm, open-label phase 0 first-in-human trial (NCT03020017) to determine safety, pharmacokinetics, intratumoral accumulation and gene-suppressive activity of systemically administered SNAs carrying siRNA specific for the GBM oncogene Bcl2Like12 (Bcl2L12). Patients with recurrent GBM were treated with intravenous administration of siBcl2L12-SNAs (drug moniker: NU-0129), at a dose corresponding to 1/50th of the no-observed-adverse-event level, followed by tumor resection. Safety assessment revealed no grade 4 or 5 treatment–related toxicities. Inductively coupled plasma mass spectrometry, x-ray fluorescence microscopy, and silver staining of resected GBM tissue demonstrated that intravenously administered SNAs reached patient tumors, with gold enrichment observed in the tumor-associated endothelium, macrophages, and tumor cells. NU-0129 uptake into glioma cells correlated with a reduction in tumor-associated Bcl2L12 protein expression, as indicated by comparison of matched primary tumor and NU-0129–treated recurrent tumor. Our results establish SNA nanoconjugates as a potential brain-penetrant precision medicine approach for the systemic treatment of GBM.

Improving composite battery electrodes requires a delicate control of active materials and electrode formulation. The electrochemically active particles fulfill their role as energy exchange reservoirs through interacting with the surrounding conductive network. We formulate a network evolution model to interpret the regulation and equilibration between electrochemical activity and mechanical damage of these particles. Through statistical analysis of thousands of particles using x-ray phase contrast holotomography in a LiNi 0.8 Mn 0.1 Co 0.1 O 2 -based cathode, we found that the local network heterogeneity results in asynchronous activities in the early cycles, and subsequently the particle assemblies move toward a synchronous behavior. Our study pinpoints the chemomechanical behavior of individual particles and enables better designs of the conductive network to optimize the utility of all the particles during operation.

The ability to precisely arrange molecules or particles on the nanometer scale is an opportunity approached from many experimental perspectives. Molecular self-assembly is particularly promising for "bottom-up" nanofabrication because of its versatility and potential ease to pattern features on the nanometer size scale unavailable with conventional "top-down" (e.g., lithography) methods. Facile control of the size, shape, and spatial distribution of nanoparticles, proteins, and biomolecules creates opportunities with applications in fields ranging from nanoelectronics to biosensing. In a recent review, Kotov et al. described particular interest in one-dimensional nanostructures constructed by the linear assembly of inorganic nanoparticles because of the interparticle electronic, photonic, and energy transfer properties which give rise to potential device applications as well as provide model systems for the fundamental understanding of interparticle nanometer-scale phenomena.[1] Currently, there are a variety of solution-based assembly strategies being explored for the fabrication of linear inorganic nanoparticle assemblies. Most of these solution assembly strategies involve the use of a linear template such as polymers [2] or carbon nanotubes.[3] Biological molecules offer great potential for use in such applications because of the complexity of nanostructures they can inherently form and the ability to design multiple types and numbers of interactions within the same molecule. [4,5] DNA is a widely used template and has been shown by Seeman [6][7][8] and others [9][10][11][12][13] to be useful as a programmable two-dimensional template for the organization of inorganic nanoparticle arrays. Protein-based materials such as collagen, [14] microtubules, [15] amyloid fibrils, [16] viruses, [17][18][19] and de novo designed peptide assemblies [20][21][22][23][24] are a few examples of linear templates used for constructing 1D nanoparticle assemblies. Despite the diversity of templates employed thus far, most attempts, with the exception of DNA, have resulted in linear nanoparticle assemblies without specific control over relative particle placement. In this Communication, we demonstrate the ability of a de novo designed peptide-based template, formed through simple solution-based self-assembly and exhibiting a unique nontwisted, laminated morphology, [25] to produce periodically spaced, parallel, linear nanoparticle arrays. Research in the Pochan and Schneider groups has focused on the design of peptides and the understanding of their selfassembly behavior for biomaterials applications in tissue engineering as well as the current interest in construction of peptide-inorganic hybrid materials for potential nanotechnology applications. [25][26][27][28][29][30] Synthetic peptides can be designed to adopt specific secondary conformations, such as an a-helix or b-sheet, by utilization of specific design motifs. In turn, intermolecular interactions can be utilized to direct the formation of complex, hierarchical assemblies...

Self-assembly represents a robust and powerful paradigm for the bottom-up construction of nanostructures. Templated condensation of silica precursors on self-assembled nanoscale peptide fibrils with various surface functionalities can be used to mimic biosilicification. This template-defined approach toward biomineralization was utilized for the controlled fabrication of 3D hybrid nanostructures. The peptides MAX1 and MAX8 used herein form networks consisting of interconnected, self-assembled β-sheet fibrils. We report a study on the structure–property relationship of self-assembled peptide hydrogels where mineralization of individual fibrils through sol–gel chemistry was achieved. The nanostructure and consequent mechanical characteristics of these hybrid networks can be modulated by changing the stoichiometric parameters of the sol–gel process. The physical characterization of the hybrid networks via electron microscopy and small-angle scattering is detailed and correlated with changes in the network mechanical behavior. The resultant high fidelity templating process suggests that the peptide substrate can be used to template the coating of other functional inorganic materials.

Nickel hydroxide represents a technologically important material for energy storage, such as hybrid supercapacitors. It has two different crystallographic polymorphs, α‐ and β‐Ni(OH)2, showing advantages in either theoretical capacity or cycling/rate performance, manifesting a trade‐off trend that needs to be optimized for practical applications. Here, the synergistic superiorities in both activity and stability of corrugated β‐Ni(OH)2 nanosheets are demonstrated through an electrochemical abuse approach. With ≈91% capacity retention after 10 000 cycles, the corrugated β‐Ni(OH)2 nanosheets can deliver a gravimetric capacity of 457 C g−1 at a high current density of 30 A g−1, which is nearly two and four times that of the regular α‐ and β‐Ni(OH)2, respectively. Operando spectroscopy and finite element analysis reveal that greatly enhanced chemical activity and structural robustness can be attributed to the in situ tailored lattice defects and the strain‐induced highly curved micromorphology. This work demonstrates a multi‐scale defect‐and‐strain co‐design strategy, which is helpful for rational design and tuned fabrication of next‐generation electrode materials for stable and high‐rate energy storage.

The study of interactions between particles organized in a linear configuration is interesting from a quantum mechanical perspective, and the anisotropic properties of linear assemblies is of potential interest for the development of solid-state devices. [1][2][3] This anisotropy may be manifested as a difference in the magnetization and coercivity obtained in a magneticnanoparticle array when a field is applied along the chain or orthogonal to it. [4,5] Nonlinear electrical characteristics [3] or dichroism in the optical spectra with longitudinal and transverse polarizations of light [6,7] in metal nanoparticle arrays are other examples of such anisotropy, and the construction of such arrays would offer opportunities in multiple applications. Engineering matter at submicron length scales has been an area largely dominated by top-down methodologies. Control of interparticle spacing in metal-nanoparticle arrays by using techniques such as electron beam lithography has been found to have a dramatic impact on the optical response of the nanoparticle assembly, [8][9][10] and has implications in fields such as plasmonics [11] and energy transport. [12,13] The use of templates such as carbon nanotubes [14] and linear pores [15] to construct one-dimensional nanostructures has been demonstrated previously. In addition, polymers have recently begun to play an increasingly active role as elements that can reproducibly direct the arrangement of nanoparticles into functional geometries. [16,17] Self assembling systems offer convenient yet powerful bottom-up strategies for the creation of nanostructures that can be deployed in the realization of functional nanoscale devices. [18,19] The utilization of biomolecules such as DNA, [3,[20][21][22][23][24] and protein-based materials [25][26][27] or viruses [28,29] to dictate the organization of nanoparticles has been shown to be an effective and robust paradigm. The use of peptide-based structures [30,31] in nanotechnology confers numerous advantages such as the specification of assembled nanostructure by changes in the primary sequence of the peptide, as well as the adoption of various hierarchical morphologies in solution. [32][33][34][35] This approach consequently permits the engineering of chemical functionality at precise positions in the nanoarchitecture of the assembled morphology. This functionality can be highly selective toward the binding of different inorganic materials [36] and may be engineered for biological recognition.[37] Herein, we demonstrate the construction of one-dimensional gold nanoparticle arrays with precise axial separations using self-assembling polypeptide fibrils. We elucidate the self-assembly of an alanine-rich polypeptide (designated 17H6) into fibrils that present regularly spaced charged patches along the fibril length. These positively charged patches are then utilized for the electrostatic binding of oppositely charged inorganic nanoparticles, thus resulting in linear nanoparticle arrays. The nanoparticles are immobilized on the fibril templa...