A Pseudolayered MoS2 as Li‐Ion Intercalation Host with Enhanced Rate Capability and DurabilityGong, Shan; Zhao, Guangyu; Lyu, Pengbo; Sun, Kening
doi: 10.1002/smll.201803344pmid: 30345625
As a popular strategy, interlayer expansion significantly improves the Li‐ion diffusion kinetics in the MoS2 host, while the large interlayer spacing weakens the van der Waals force between MoS2 monolayers, thus harming its structural stability. Here, an oxygen‐incorporated MoS2 (O‐MoS2)/graphene composite as a self‐supported intercalation host of Li‐ion is prepared. The composite delivers a specific capacity of 80 mAh g−1 in only 36 s at a mass loading of 1 mg cm−2, and it can be cycled 3000 times (over 91% capacity retention) with a 5 mg cm−2 loading at 2 A g−1. The O‐MoS2 exhibits a dominant 1T phase with an expanded layer spacing of 10.15 Å, leading to better Li‐ion intercalation kinetics compared with pristine MoS2. Furthermore, ex situ X‐ray diffraction tests indicate that O‐MoS2 sustains a stable structure in cycling compared with the gradual collapse of pristine MoS2, which suffers from excessive lattice breathing. Density functional theory calculations suggest that the MoOx(OH)y pillars in O‐MoS2 interlayers not only expand the layer spacing, but also tense the MoS2 layers to avoid exfoliation in cycling. Therefore, the O‐MoS2 shows a pseudolayered structure, leading to remarkable durability besides the outstanding rate capability as a Li‐ion intercalation host.
Electroactive Scaffolds for Neurogenesis and Myogenesis: Graphene‐Based NanomaterialsZhang, Zhongyang; Klausen, Lasse Hyldgaard; Chen, Menglin; Dong, Mingdong
doi: 10.1002/smll.201801983pmid: 30264534
One of the major issues in tissue engineering is constructing a functional scaffold to support cell growth and also provide proper synergistic guidance cues. Graphene‐based nanomaterials have emerged as biocompatible and electroactive scaffolds for neurogenesis and myogenesis, due to their excellent tunable chemical, physical, and mechanical properties. This review first assesses the recent investigations focusing on the fabrication and applications of graphene‐based nanomaterials for neurogenesis and myogenesis, in the form of either 2D films, 3D scaffolds, or composite architectures. Besides, because of their outstanding electrical properties, graphene family materials are particularly suitable for designing electroactive scaffolds that could provide proper electrical stimulation (i.e., electrical or photo stimuli) to promote the regeneration of excitable neurons and muscle cells. Therefore, the effects and mechanism of electrical and/or photo stimulations on neurogenesis and myogenesis are followed. Furthermore, studies on their biocompatibilities and toxicities especially to neural and muscle cells are evaluated. Finally, the future challenges and perspectives in facilitating the development of clinical translation of graphene‐family nanomaterials in treating neurodegenerative and muscle diseases are discussed.
Scalable 3D Nanoparticle Trap for Electron Microscopy AnalysisSun, Xingwu; Berenschot, Erwin J. W.; Veltkamp, Henk‐Willem; Gardeniers, Han J. G. E.; Tas, Niels R.
doi: 10.1002/smll.201803283pmid: 30324725
Arrays of nanoscale pyramidal cages embedded in a silicon nitride membrane are fabricated with an order of magnitude miniaturization in the size of the cages compared to previous work. This becomes possible by combining the previously published wafer‐scale corner lithography process with displacement Talbot lithography, including an additional resist etching step that allows the creation of masking dots with a size down to 50 nm, using a conventional 365 nm UV source. The resulting pyramidal cages have different entrance and exit openings, which allows trapping of nanoparticles within a predefined size range. The cages are arranged in a well‐defined array, which guarantees traceability of individual particles during post‐trapping analysis. Gold nanoparticles with a size of 25, 150, and 200 nm are used to demonstrate the trapping capability of the fabricated devices. The traceability of individual particles is demonstrated by transferring the transmission electron microscopy (TEM) transparent devices between scanning electron microscopy and TEM instruments and relocating a desired collection of particles.
Highly Fluorescent and Stable Black Phosphorus Quantum Dots in WaterLong, Liyuan; Niu, Xianghong; Yan, Kun; Zhou, Gang; Wang, Jinlan; Wu, Xinglong; Chu, Paul K.
doi: 10.1002/smll.201803132pmid: 30307702
Although 2D black phosphorus (BP) shows excellent optical and electronic properties, there are few reports on the photoluminescence (PL) properties of BP nanostructures because of the low yield of mechanical exfoliation, instability in water, and relatively weak emission. Herein, liquid exfoliation is combined with surface passivation to produce fluorescent BP quantum dots (BPQDs) with a high yield. The BPQDs exhibit strong PL in both ethanol and water and the absolute fluorescent quantum yield in water reaches 70%. Moreover, the BPQD solution exhibits stable PL for 150 d under ambient conditions and better photostability than conventional organic dyes and heavy‐metal semiconducting nanostructures with intense fluorescence. The experiments and theoretical calculation reveal that the intense and stable PL originates from the intrinsic band‐to‐band excitation states and two surface states related to the POH and POCH2CH3 bonding structures introduced by passivation. The polar water molecules remove many nonradiative centers and simultaneously increase the P‐related fluorescent groups on the surface of BPQDs. Therefore, PL from the BPQDs in water is enhanced largely. The excellent fluorescent properties of BPQDs in an aqueous solution bode well for bioimaging and the negligible biotoxicity and distinct cell images suggest large potential in the biomedical and display fields.
Spontaneous Reshaping and Splitting of AgCl Nanocrystals under Electron Beam IlluminationTian, Xuezeng; Anand, Utkarsh; Mirsaidov, Utkur; Zheng, Haimei
doi: 10.1002/smll.201803231pmid: 30369027
AgCl is photosensitive and thus often used as micromotors. However, the dynamics of individual AgCl nanoparticle motion in liquids upon illumination remains elusive. Here, using liquid cell transmission electron microscope (TEM), AgCl nanocrystals reshaping and splitting spontaneously in an aqueous solution under electron beam illumination are observed. It is found that the AgCl nanocrystals are negatively charged in the liquid environment, where the charge induces a repulsive Coulomb force that reshapes and stretches those nanocrystals. Upon extensive stretching, the AgCl nanocrystal splits into small nanocrystals and each nanocrystal retracts back into cuboid shapes due to the cohesive surface. This analysis shows that each nanocrystal maintains a single crystal rocksalt structure during splitting. The splitting of AgCl nanocrystals is analogous to the electrified liquid droplets or other reported the Coulomb fission phenomenon, but with distinctive structural properties. Revealing of the dynamic behavior of AgCl nanocrystals opens the opportunity to explore their potential applications as actuators for nanodevices.
A Tailored Bifunctional Electrocatalyst: Boosting Oxygen Reduction/Evolution Catalysis via Electron Transfer Between N‐Doped Graphene and Perovskite OxidesBu, Yunfei; Nam, Gyutae; Kim, Seona; Choi, Keunsu; Zhong, Qin; Lee, JunHee; Qin, Yong; Cho, Jaephil; Kim, Guntae
doi: 10.1002/smll.201802767pmid: 30226302
Fabricating perovskite oxide/carbon material composite catalysts is a widely accepted strategy to enhance oxygen reduction reaction/oxygen evolution reaction (ORR and OER) catalytic activities. Herein, synthesized, porous, perovskite‐type Sm0.5Sr0.5CoO3‐δ hollow nanofibers (SSC‐HF) are hybridized with cross‐linked, 3D, N‐doped graphene (3DNG). This rationally designed hybrid catalyst, SSC‐HF‐3DNG (SSC‐HG), exhibits a remarkable enhancement in ORR/OER activity in alkaline media. The synergistic effects between SSC and 3DNG during their ORR and OER processes are firstly revealed by density functional theory calculations. It suggests that electron transport from 3DNG to O2 and SSC increases the activity of electrocatalytic reactions (ORR and OER) by activating O2, increasing the covalent bonding of lattice oxygen. This electron transfer–accelerated catalysis behavior in SSC‐HG will provide design guidelines for composites of perovskite and carbon with bifunctional catalysts.
Microparticle Delivery of Protein Markers for Single‐Cell Western Blotting from MicrowellsKim, John J.; Chan, Peggy P. Y.; Vlassakis, Julea; Geldert, Alisha; Herr, Amy E.
doi: 10.1002/smll.201802865pmid: 30334351
Immunoblotting confers protein identification specificity beyond that of immunoassays by prepending protein electrophoresis (sizing) to immunoprobing. To accurately size protein targets, sample analysis includes concurrent analysis of protein markers with known molecular masses. To incorporate protein markers in single‐cell western blotting, microwells are used to isolate individual cells and protein marker‐coated microparticles. A magnetic field directs protein‐coated microparticles to >75% of microwells, so as to 1) deliver a quantum of protein marker to each cell‐laden microwell and 2) synchronize protein marker solubilization with cell lysis. Nickel‐coated microparticles are designed, fabricated, and characterized, each conjugated with a mixture of histidine‐tagged proteins (42.3–100 kDa). Imidazole in the cell lysis buffer solubilizes protein markers during a 30 s cell lysis step, with an observed protein marker release half‐life of 4.46 s. Across hundreds of individual microwells and different microdevices, robust log‐linear regression fits (R2 > 0.97) of protein molecular mass and electrophoretic mobility are observed. The protein marker and microparticle system is applied to determine the molecular masses of five endogenous proteins in breast cancer cells (GAPDH, β‐TUB, CK8, STAT3, ER‐α), with <20% mass error. Microparticle‐delivered protein standards underpin robust, reproducible electrophoretic cytometry that complements single‐cell genomics and transcriptomics.