Small Methods最新文献

This study reveals a local strain-dependent etching behavior that enables the formation of distinguished etching patterns in differently strained chemical vapor deposited (CVD) 2D molybdenum disulfide (MoS₂) monolayers. It is demonstrated that when the local tensile strain of CVD 2D MoS₂ is as uniformly low as ɛ ≈ 0.33% or less, the oxidative etching pattern possesses conventional triangular etching pits (TEPs), while when the local tensile strain is as uniformly high as ɛ ≈ 0.55% or larger, the oxidative etching pattern consist of uniformly oriented hexagonal etching channels (HECs). More interestingly, when the CVD 2D MoS₂ monolayer has heterogenous strain distribution from ɛ ≈ 0.55% (center region) to ɛ ≈ 0.33% (perimeter region), the oxidative etching pattern comprise of non-uniformly hexagonal-mixed-parallel etching channels (HPECs). The further characterization and analysis reveal the formation mechanism of such strain-dependent etching patterns is built on the local strain-related fractures propagation under oxidative etching, as well as the anisotropy fractures-based oxidative etching kinetics. This study may enhance the understanding of the relationship between etching and growth features of 2D TMDs, and paves the way to etching-nanostructured (or defect) engineering of 2D TMDs and other 2D materials for potential applications in electrocatalysis and optoelectronics.

Van der Waals (vdW) heterostructures comprising of transition metal dichalcogenides (TMDs) and hexagonal boron nitride (h-BN) are promising building blocks for novel 2D devices. The vdW epitaxy provides a straightforward integration method for fabricating high-quality TMDs/h-BN vertical heterostructures. In this work, the vdW epitaxy of high-quality single-crystal HfSe₂ on epitaxial h-BN/sapphire substrates by chemical vapor deposition is demonstrated. The epitaxial HfSe₂ layers exhibit a uniform and atomically sharp interface with the underlying h-BN template, and the epitaxial relationship between HfSe₂ and h-BN/sapphire is determined to HfSe₂ (0001)[1 $\overline{2}$ 10]//h-BN (0001)[1 $\overline{1}$ 00]//sapphire (0001)[1 $\overline{1}$ 00]. Impressively, the full width at half maximum of the rocking curve for the epitaxial HfSe₂ layer on single-crystal h-BN is as narrow as 9.6 arcmin, indicating an extremely high degree of out-plane orientation and high crystallinity. Benefitting from the high crystalline quality of HfSe₂ epilayers and the weak interfacial scattering of HfSe₂/h-BN, the photodetector fabricated from the vdW epitaxial HfSe₂ on single-crystal h-BN shows the best performance with an on/off ratio of 1 × 10⁴ and a responsivity up to 43 mA W^-1. Furthermore, the vdW epitaxy of other TMDs such as HfS₂, ZrS₂, and ZrSe₂ is also experimentally demonstrated on single-crystal h-BN, suggesting the broad applicability of the h-BN template for the vdW epitaxy.

Perovskite crystallization regulation is essential to obtain excellent film optoelectronic properties and device performances. However, rapid crystallization during annealing always results in poor perovskite film and easy formation of trap, thereby greatly restricting device performance due to severe non-radiative recombination. Here, an easy and reproducible gradient thermal annealing (GTA) approach is used to regulate the perovskite crystallization. Through a low-temperature initial annealing of GTA, the solvent evaporation is slowed down, thus extending nucleation time and providing a buffer for the rapid crystallization of perovskite grains in the subsequent high-temperature stage. As a result, completely converted and highly crystalline perovskite is obtained with 1.6 times larger grain size, reduced trap density and suppressed non-radiative recombination of photo-generated carriers. The film crystallinity is also enhanced with more advantageous (100) and (111) lattice facets which are favorable for carrier transport. Consequently, the perovskite photodetectors exhibit a large linear dynamic range of 174 dB and an excellent response even under ultra-weak light of 303 pW. Meanwhile, perovskite solar cells achieved increased PCE and maintained 85% of original efficiency after heating at 65 °C for nearly 1000 h under unencapsulated conditions. To the knowledge, this represents the best performance reported for a perovskite photovoltaic-photodetection bifunctional device.

The CRISPR-Cas systems are adopted as powerful molecular tools for not only genetic manipulation but also point-of-care diagnostics. However, methods to enable diagnostics of non-nucleic-acid targets with these systems are still limited. Herein, by fusing ligand-dependent allosteric ribozymes with CRISPR-Cas12a, a derived CRISPR-Cas system is created for efficient quantitative analysis of non-nucleic-acid targets in 1-2 h. On two different small molecules, the system's generality, reliability and accuracy is demonstrated, and show that the well operability of this system can enable high-throughput detection of a small molecule in blood samples. The system can be further converted to rely on allosteric deoxyribozyme instead of allosteric ribozyme to recognize non-nucleic-acid targets and transduce the signal to CRISPR-Cas12a for amplification, likely making it easier for storage and more consistent in data generation as DNA possess a stability advantage over RNA. This (deoxy)ribozyme-assisted CRISPR-Cas12a system anticipates that it can facilitate bioanalysis in various scientific and clinical settings and further drive the development of clinical translation.

The crumpling and buckling in nanosheets are anticipated to provide new characteristics that could not be observed in ideal flat layers. However, the rigid lattice structure of inorganic metal oxides limits their assembly into well-defined crumpled layers. Here, this study demonstrates that at the sub-nm scale, polyoxometalates (POMs) clusters having well-defined structures can intercede during the nucleation process of titania and co-assemble with nuclei to form uniform, large-sized crumpled binary 2D layers with a thickness of 2 nm. The obtained crumpled layers are then used as a support material to immobilize Pd nanoclusters with an average size of 2 nm. Pd-immobilized crumpled layers are employed as heterogeneous catalysts for the partial hydrogenation of acetylene. This structurally and compositionally unique heterogeneous catalyst manifests exceptional selectivity to cis-alkene with almost 100% yield as compared to commercially available titania which only exhibits 10% diphenylacetylene conversion and 42% selectivity in the given period of time.

Carbon-supported nitrogen-coordinated iron single-atom (Fe-N-C) catalysts have been regarded among the most promising platinum-group-metal-free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Nevertheless, their limited intrinsic activity and unsatisfactory stability have hindered their practical applications. Here, it is reported that the integration of Mo₂C clusters effectively enhances the ORR activity and stability of Fe-N-C catalysts. The composite catalyst of Fe single atoms and Mo₂C clusters co-embedded on nitrogen-doped carbon (Fe_SA/Mo₂C-NC) exhibits an excellent ORR activity with a half-wave potential of 0.82 V in acidic media and a high peak power density of 0.5 W cm^-2 in an H₂-air PEMFC. Moreover, improved stability is achieved with nearly no decay under H₂-air conditions for 80 h at 0.4 V. Experiments with theoretical calculations elucidate that the etching effect of the phosphomolybdic acid precursor optimizes the pore size distribution of the composite catalyst, thereby exposing more active sites. The Mo₂C clusters modulate the electronic configuration of the Fe-N₄ sites, optimizing adsorption energy for ORR intermediates and strengthening the Fe-N bond to mitigate demetalation. This work provides valuable insights into the construction of single-atom/nanoaggregate hybrid catalysts for efficient energy-related applications.

Androgenetic alopecia (AGA) is a prevalent issue affecting the physical and mental health of individuals but with fewer current treatments. Platinum nanozymes (PtNZs) are known for their excellent ability to reduce and modulate the high oxidative stress environment in AGA pathology. And microneedles are used to overcome the skin barrier due to the poor permeability of PtNZs. Herein, dissolving microneedles loaded with PtNZs (Pt-MNs) are designed and successfully induced hair regeneration in the AGA model. Pt-MNs possessed adequate mechanical strength to breach the skin barrier for effective PtNZs delivery. In vivo, PtNZs first reduced reactive oxygen species (ROS) to oxygen, which recovered the AGA pathological environment. And the oxygen then increased oxidative phosphorylation, promoting the differentiation of hair follicle stem cells to achieve hair regeneration. The group treated with Pt-MNs with a dosing frequency of once every three days achieved faster hair growth than the daily application of the positive drug minoxidil. Further safety experiments showed that the application of Pt-MNs locally opened temporary and recoverable skin channels, with no retention of Pt in major organs, indicating high safety. In conclusion, this study indicated the potential of Pt-MNs as an effective method for treating AGA.

Angstrom-scale fluidic channels offer immense potential for applications in areas such as desalination, molecular sieving, biomolecular sequencing, and dialysis. Inspired by biological ion channels, nano- and angstrom (Å)-scale channels are fabricated that mimic these molecular or atomic-scale dimensions. At the Å-scale, these channels exhibit unique phenomena, including selective ion transport, osmotic energy generation, fast water and gas flows, and neuromorphic ion memory. However, practical utilization of Å-scale channels is often hindered by contamination, which can clog these nanochannels. In this context, a promising technique is introduced here for unclogging 2D channels, particularly those with sub-nanometre dimensions (≈6.8 Å). The voltage-cycling method emerges as an efficient and reliable solution for this challenge. The electric field effectively dislodges contaminants from the clogged Å-scale channels, facilitating ion and molecular transport. This study provides practical guidelines for reviving clogged nano- and Å-scale channels, thereby enhancing their applicability in various ion and molecular transport applications.

Human parathyroid hormone (1-34) (PTH) exhibits osteoanabolic and osteocatabolic effects, with shorter plasma exposure times favoring bone formation. Subcutaneous injection (SCI) is the conventional delivery route for PTH but faces low delivery efficiency due to limited passive diffusion and the obstruction of the vascular endothelial barrier, leading to prolonged drug exposure times and reduced osteoanabolic effects. In this work, a microcurrent delivery system (MDS) based on multimicrochannel microneedle arrays (MMAs) is proposed, achieving high efficiency and safety for PTH transdermal delivery. The internal microchannels of the MMAs are fabricated using high-precision 3D printing technology, providing a concentrated and safe electric field that not only accelerates the movement of PTH but also reversibly increases vascular endothelial permeability by regulating the actin cytoskeleton and interendothelial junctions through Ca²⁺-dependent cAMP signaling, ultimately promoting PTH absorption and shortening exposure times. The MDS enhances the osteoanabolic effect of PTH in an osteoporosis model by inhibiting osteoclast differentiation on the bone surface compared to SCI. Moreover, histopathological analysis of the skin and organs demonstrated the good safety of PTH delivered by MDS in vivo. In addition to PTH, the MDS shows broad prospects for the high-efficiency transdermal delivery of macromolecular drugs.

Inside Front Cover

In article number 2400757, Liao, Huang, Lei, and co-workers developed a novel nanozyme which employs an “In-Out” strategy to restore the cartilage lubrication system. The “Out” aspect aims to decrease friction and minimize the wear and tear on cartilage, while the “In” aspect is focused on alleviating oxidative stress to facilitate the production and secretion of lubricin, thereby enhancing the natural lubrication capacity of cartilage.