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Abstract Single-photon emitters are crucial building blocks for optical quantum technologies. Hexagonal boron nitride (hBN) is a promising two-dimensional material that hosts bright, room-temperature single-photon emitters. However, photo instability is a persistent challenge preventing practical applications of these properties. Here, we reveal the ubiquitous photobleaching of hBN vacancy emitters. Independent of the source or the number of hBN layers, we find that the photobleaching of a common emission at 1.98 ± 0.05 eV can be described by two consistent time constants, namely a first bleaching lifetime of 5 to 10 s, and a second bleaching lifetime in the range of 150 to 220 s. Only the former is environmentally sensitive and can be significantly mitigated by shielding O₂, whereas the latter could be the result of carbon-assisted defect migration. Annular dark-field scanning transmission electron microscopy of photobleached hBN allows for visualizing vacancy defects and carbon substitution at single atom resolution, supporting the migration mechanism along with X-ray photoelectron spectroscopy. Thermal annealing at 850 °C of liquid exfoliated hBN eliminates both bleaching processes, leading to persistent photostability. These results represent a significant advance to potentially engineer hBN vacancy emitters with the photostability requisite for quantum applications. 

Abstract Nanoparticle corona phases, especially those surrounding anisotropic particles, are central to determining their catalytic, molecular recognition, and interfacial properties. It remains a longstanding challenge to chemically synthesize and control such phases at the nanoparticle surface. In this work, the supramolecular chemistry of rosette nanotubes (RNTs), well‐defined hierarchically self‐assembled nanostructures formed from heteroaromatic bicyclic bases, is used to create molecularly precise and continuous corona phases on single‐walled carbon nanotubes (SWCNTs). These RNT–SWCNT (RS) complexes exhibit the lowest solvent‐exposed surface area (147.8 ± 60m⁻¹) measured to date due to its regular structure. Through Raman spectroscopy, molecular‐scale control of the free volume is also observed between the two annular structures and the effects of confined water. SWCNT photoluminescence (PL) within the RNT is also modulated considerably as a function of their diameter and chirality, especially for the (11, 1) species, where a PL increase compared to other species can be attributed to their chiral angle and the RNT's inward facing electron densities. In summary, RNT chemistry is extended to the problem of chemically defining both the exterior and interior corona interfaces of an encapsulated particle, thereby opening the door to precision control of core–shell nanoparticle interfaces. 

Abstract Nanosensors have proven to be powerful tools to monitor single cells, achieving spatiotemporal precision even at molecular level. However, there has not been way of extending this approach to statistically relevant numbers of living cells. Herein, we design and fabricate nanosensor array in microfluidics that addresses this limitation, creating a Nanosensor Chemical Cytometry (NCC). nIR fluorescent carbon nanotube array is integrated along microfluidic channel through which flowing cells is guided. We can utilize the flowing cell itself as highly informative Gaussian lenses projecting nIR profiles and extract rich information. This unique biophotonic waveguide allows for quantified cross-correlation of biomolecular information with various physical properties and creates label-free chemical cytometer for cellular heterogeneity measurement. As an example, the NCC can profile the immune heterogeneities of human monocyte populations at attomolar sensitivity in completely non-destructive and real-time manner with rate of ~600 cells/hr, highest range demonstrated to date for state-of-the-art chemical cytometry. 

Abstract Single‐layer graphene containing molecular‐sized in‐plane pores is regarded as a promising membrane material for high‐performance gas separations due to its atomic thickness and low gas transport resistance. However, typical etching‐based pore generation methods cannot decouple pore nucleation and pore growth, resulting in a trade‐off between high areal pore density and high selectivity. In contrast, intrinsic pores in graphene formed during chemical vapor deposition are not created by etching. Therefore, intrinsically porous graphene can exhibit high pore density while maintaining its gas selectivity. In this work, the density of intrinsic graphene pores is systematically controlled for the first time, while appropriate pore sizes for gas sieving are precisely maintained. As a result, single‐layer graphene membranes with the highest H₂/CH₄separation performances recorded to date (H₂permeance > 4000 GPU and H₂/CH₄selectivity > 2000) are fabricated by manipulating growth temperature, precursor concentration, and non‐covalent decoration of the graphene surface. Moreover, it is identified that nanoscale molecular fouling of the graphene surface during gas separation where graphene pores are partially blocked by hydrocarbon contaminants under experimental conditions, controls both selectivity and temperature dependent permeance. Overall, the direct synthesis of porous single‐layer graphene exploits its tremendous potential as high‐performance gas‐sieving membranes.