Dopamine-integrated all-hydrogel multi-electrode arrays for neural activity recording.

Investigation of brain neural circuits is essential for deciphering the diagnostics and therapeutics of neurodegenerative diseases. The main concerns with traditional rigid metal electrodes include intrinsic mechanical mismatch between sensing electrodes and tissues, unavoidable foreign body responses, and inadequate spatiotemporal resolution, resulting in a deficiency of sensing performance. All-hydrogel neural electrodes with multi-electrode arrays (MEAs) suggest a viable way to modulate the trade-off between tissue-mechanical compliance and excellent spatiotemporal recording capacity, but still face the issues of insufficient conductivity and unstable interlayer bonding. Herein, we constructed a four-layer all-hydrogel neural electrode, by sandwiching a conductive hydrogel layer within two encapsulation hydrogel layers, with a shielding hydrogel layer located on top. We introduce a dual-strategy treatment to induce controllable phase separation in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hydrogel, which achieved ultra-high conductivity (up to 4176 S cm-1) comparable to that of metals and precise spatial resolution (∼15 µm) suitable for single neuron recording. In addition, the utilization of polyphenol chemistry mediated adaptive adhesion endowed this neural electrode with flexible and stable interlayer bonding among conductive-encapsulation-shielding layers and the tissue-electrode interface. Consequently, the all-hydrogel neural electrode exhibited a tenfold higher signal-to-noise ratio than a commercial silver electrode, realized the recording of weak neural activity signals within single and multiple neurons in epileptic rats, and applied man-made stimulation to the cerebral cortex of rats during seizures. This work provides a useful tool to understand the development, function and treatment of neurodegenerative diseases.

Synergistic Performance of Thermoelectric and Mechanical in Nanotwinned High-Entropy Semiconductors AgMnGePbSbTe5.

Introducing nanotwins in thermoelectric materials represents a promising approach to achieving such a synergistic combination of thermoelectric properties and mechanical properties. By increasing configurational entropy, a sharply reduced stacking fault energy in a new nanotwinned high-entropy semiconductor AgMnGePbSbTe5 is reached. Dense coherent nanotwin boundaries in this system provide an efficient phonon scattering barrier, leading to a high figure of merit ZT of ≈2.46 at 750 K and a high average ZT of ≈1.54 (300-823 K) with the presence of Ag2Te nanoprecipitate in the sample. More importantly, owing to the dislocation pinning caused by coherent nanotwin boundaries and the chemical short-range disorder caused by the high configurational entropy effect, AgMnGePbSbTe5 also exhibits robust mechanical properties, with flexural strength of 82 MPa and Vickers hardness of 210 HV.

Rapid profiling of fish cell nitrogen metabolism with single-cell Raman spectroscopy: Unveiling enzyme's role in ammonia detoxification.

Ammonia is a prevalent aquatic pollutant that disrupts cellular functions and energy metabolism in fish, posing significant environmental and health threats. This research investigates the critical role of arginase 2 (ARG2) in mitigating ammonia toxicity in fish cells and its implications in adapting to nitrogen metabolism under high ammonia exposure. Through a CRISPR-Cas9 engineered ARG2 knockdown (KD) in the Epithelioma Papulosum Cyprini (EPC) cell line, we first investigated the biochemical responses of ARG2 KD and wild-type (WT) EPC cells to ammonia stress (NH4Cl treatment), showing diminished urea production and decreased cell viability in ARG2 KD cells. Subsequently, single-cell Raman spectroscopy analysis revealed that ARG2 KD cells exhibited profound metabolic shifts, including changes in protein, nucleic acids, lipid and sugar levels, showing the adjusting role of ARG2 in the balance of carbohydrate and nitrogen metabolism. Furthermore, the upregulated responses of various amino acids, such as glutamine, arginine, alanine, glutamic acid, glycine, histidine, phenylalanine and valine, in WT cells after NH4Cl treatment diminished in ARG2 KD cells except for the decrease in aspartic acid, indicating a switching effect of ARG2 in nitrogen metabolism under ammonia stress. This study highlights ARG2's essential role in ammonia detoxification and emphasizes ARG2's protective function and its importance in metabolism, shedding light on the adaptive mechanisms fish cells deploy against high ammonia environments. These insights contribute to deep understanding of aquatic organisms' molecular responses to environmental ammonia pollution, offering potential strategies for their protection.

Investigating Communication Dynamics in Neuronal Network using 3D Gold Microelectrode Arrays.

Although in vitro neuronal network models hold great potential for advancing neuroscience research, with the capacity to provide fundamental insights into mechanisms underlying neuronal functions, the dynamics of cell communication within such networks remain poorly understood. Here, we develop a customizable, polymer modified three-dimensional gold microelectrode array with sufficient stability for high signal-to-noise, long-term, neuronal recording of cultured networks. By using directed spatial and temporal patterns of electrical stimulation of cells to explore synaptic-based communication, we monitored cell network dynamics over 3 weeks, quantifying communication capability using correlation heatmaps and mutual information networks. Analysis of synaptic delay and signal speed between cells enabled us to establish a communication connectivity model. We anticipate that our discoveries of the dynamic changes in communication across the neuronal network will provide a valuable tool for future studies in understanding health and disease as well as in developing effective platforms for evaluating therapies.

Stress-Relief Engineering in a N-Doped C-Modified Hierarchical Nanoporous Si Anode with a Microcurved Pore Wall Structure for Enhanced Lithium Storage.

The commercialization of alloy-type anodes has been hindered by rapid capacity degradation due to volume fluctuations. To address this issue, stress-relief engineering is proposed for Si anodes that combines hierarchical nanoporous structures and modified layers, inspired by the phenomenon in which structures with continuous changes in curvature can reduce stress concentration. The N-doped C-modified hierarchical nanoporous Si anode with a microcurved pore wall (N-C@m-HNP Si) is prepared from inexpensive Mg-55Si alloys using a simple chemical etching and heat treatment process. When used as the anode for lithium-ion batteries, the N-C@m-HNP Si anode exhibits initial charge/discharge specific capacities of 1092.93 and 2636.32 mAh g-1 at 0.1 C (1 C = 3579 mA g-1), respectively, and a stable reversible specific capacity of 1071.84 mAh g-1 after 200 cycles. The synergy of the hierarchical porous structure with a microcurved pore wall and the N-doped C-modified layer effectively improves the electrochemical performance of N-C@m-HNP Si, and the effectiveness of stress-relief engineering is quantitatively analyzed through the theory of elastic bending of thin plates. Moreover, the formation process of Li15Si4 crystals, which causes substantial mechanical stress, is investigated using first-principles molecular dynamic simulations to reveal their tendency to occur at different scales. The results demonstrate that the hierarchical nanoporous structure helps to inhibit the transformation of amorphous LixSi into metastable Li15Si4 crystals during lithiation.

Rapid anaerobic culture and reaction kinetic study of anammox bacteria on microfluidic chip.

Anammox bacteria are being increasingly investigated as part of an emerging nitrogen removal technology. However, due to the difficulty in culturing, current understanding of their behavior is limited. In this study, anaerobic microfluidic chips were used to study anammox bacteria, showing great advantages over reactors. On-chip fluorescence in situ hybridization (FISH) showed the relative abundance of free form anammox bacteria increased by 56.1 % after one week's culture, an increase that is three times higher than that of bioreactor (17.1 %). For granular form cultures, the nitrogen removal load reached 2.34 âˆ¼ 2.51 kg-N/(m3·d), which was also substantially higher than the bioreactor (∼1.22 kg-N/(m3·d)). Furthermore, studying the kinetics of nitrite inhibition of granular sludge with different particle sizes (100-900 µm) showed that the maximum ammonia load and the nitrite semi-saturation coefficient noticeably decreased for smaller particle sizes. These results illustrate the usefulness of the microfluidic method for in-depth understanding anammox process and its implementation.

Miniaturized Laser Probe for Exosome-Based Cancer Liquid Biopsy.

Exosomes have been established as a valuable tool for clinical applications for the purpose of liquid biopsy and therapy. However, the clinical practice of exosomes as cancer biopsy markers is still to a very low extent. Active mode optical microcavity with microlaser emission has aroused as a versatile approach for chemical and biological sensing due to its benefits of larger photon population, increased effective Q-factor, decreased line width, and improved sensitivity. Herein, we report a label-free and precise quantification of exosome vesicles and surface protein profiling of breast cancer exosomes using functionalized active whispering gallery mode (WGM) microlaser probes. A detection limit of 40 exosomes per microresonator was achieved. The proposed system enabled a pilot assay of quantitative exosome analysis in cancer patients' blood with only a few microliters of sample consumption, holding good potential for large-scale cancer liquid biopsy. Multiplexed functionalization of the optical microresonator allowed us to profile cancer exosomal surface markers and distinct subclasses of breast cancer-associated exosomes and monitor drug treatment outcomes. Our findings speak volumes about the advantages of the WGM microlaser sensor, including very small sample consumption, low detection limit, high specificity, and ease of operation, offering a promising means for precious clinical sample analysis.

Correction: Ferromagnetic and half-metallic phase transition by doping in a one-dimensional narrow-bandgap W6PCl17 semiconductor.

Correction for 'Ferromagnetic and half-metallic phase transition by doping in a one-dimensional narrow-bandgap W6PCl17 semiconductor' by Yusen Qiao et al., Nanoscale, 2023, 15, 9835-9842, https://doi.org/10.1039/D3NR01717F.

Strong spin-orbital coupling induced tunable electronic structures and enhanced visible-light absorption in one-dimensional RhTe6I3 systems.

Considering the demand for device miniaturization, low-dimensional materials have been widely employed in various fields due to their unique and fascinating physical and chemical properties. Here, based on first-principles calculations, we predict a novel one-dimensional (1D) RhTe6I3 chain system. Our calculations indicate that a 1D RhTe6I3 single chain can be prepared from its bulk counterpart by an exfoliation method and exists stably at room temperature. The 1D RhTe6I3 single chain is a direct semiconductor with a moderate bandgap of 1.75 eV under a strong spin-orbital coupling (SOC) effect dominated by Te. This bandgap can be modulated by the chain number and the application of external strain. Notably, the 1D RhTe6I3 single chain has a high electron mobility (1093 cm2 V-1 s-1), which is one to two orders of magnitude higher than those of most previously reported 1D materials. The strong SOC effect can also enhance the visible-light absorption capacity of the 1D RhTe6I3 single chain. The moderate direct bandgap, high electron mobility, excellent visible-light absorption, and strong spin-orbital coupling make 1D RhTe6I3 systems ideal candidates in electronic and optoelectronic devices.

Two-dimensional InTeClO3: an ultrawide-bandgap material with potential application in a deep ultraviolet photodetector.

Ultrawide-bandgap semiconductors, possessing bandgaps distinctly larger than the 3.4 eV of GaN, have emerged as a promising class capable of achieving deep ultraviolet (UV) light detection. Based on first-principles calculations, we propose an unexplored two-dimensional (2D) InTeClO3 layered system with ultrawide bandgaps ranging from 4.34 eV of bulk to 4.54 eV of monolayer. Our calculations demonstrate that 2D InTeClO3 monolayer can be exfoliated from its bulk counterpart and maintain good thermal and dynamic stability at room temperature. The ultrawide bandgaps may be modulated by the small in-plane strains and layer thickness in a certain range. Furthermore, the 2D InTeClO3 monolayer shows promising electron transport behavior and strong optical absorption capacity in the deep UV range. A two-probe InTeClO3-based photodetection device has been constructed for evaluating the photocurrent. Remarkably, the effective photocurrent (5.7 A m-2 at photon energy of 4.2 eV) generation under polarized light has been observed in such a photodetector. Our results indicate that 2D InTeClO3 systems have strong photoresponse capacity in the deep UV region, accompanying the remarkable polarization sensitivity and high extinction ratio. These distinctive characteristics highlight the promising application prospects of InTeClO3 materials in the field of deep UV optoelectronics.

The Isoelectronic Dopant in the Z-Scheme SnS2/ß-As Heterostructure Enhancing Photocatalytic Overall Water Splitting.

The catalytic field aims to decrease reaction barriers, accelerate reaction processes, and enhance the selectivity toward a target product. This study uses first-principles calculations to design a modified direct Z-scheme SnS2/ß-As heterostructure as a potential photocatalyst for overall water splitting. Our previous investigations have demonstrated that the SnS2/ß-As heterostructure can realize a hydrogen evolution reaction (HER) under light, while the oxygen evolution reaction (OER) follows a pathway involving the intermediate HOOH*. Interestingly, by substituting an S atom of SnS2 with a Se or Te atom, the rate-determining step of the OER is significantly reduced from 3.76 eV to 2.56 or 2.22 eV. Moreover, the OER can occur directly without the transition via HOOH*. Isoelectronic doping effectively trades off the adsorption strength of OER intermediates and promotes the OER process. This work highlights the dual benefits of isoelectronic doping, namely lowering the reaction barrier of the rate-determining step and promoting the selectivity of end products. These findings provide insights into the rational design of high-efficiency photocatalysts for water splitting.

Wireless-Powering Deep Brain Stimulation Platform Based on 1D-Structured Magnetoelectric Nanochains Applied in Antiepilepsy Treatment.

Electrical deep brain stimulation (DBS) is a top priority for pharmacoresistant epilepsy treatment, while less-invasive wireless DBS is an urgent priority but challenging. Herein, we developed a conceptual wireless DBS platform to realize local electric stimulation via 1D-structured magnetoelectric Fe3O4@BaTiO3 nanochains (FBC). The FBC was facilely synthesized via magnetic-assisted interface coassembly, possessing a higher electrical output by inducing larger local strain from the anisotropic structure and strain coherence. Subsequently, wireless magnetoelectric neuromodulation in vitro was synergistically achieved by voltage-gated ion channels and to a lesser extent, the mechanosensitive ion channels. Furthermore, FBC less-invasively injected into the anterior nucleus of the thalamus (ANT) obviously inhibited acute and continuous seizures under magnetic loading, exhibiting excellent therapeutic effects in suppressing both high voltage electroencephalogram signals propagation and behavioral seizure stage and neuroprotection of the hippocampus mediated via the Papez circuit similar to conventional wired-in DBS. This work establishes an advanced antiepilepsy strategy and provides a perspective for other neurological disorder treatment.

Anisotropic gypsum scaling of corrugated polyvinylidene fluoride hydrophobic membrane in direct contact membrane distillation.

Membrane distillation (MD) technology has gained a lot of attention for treatment of geothermal brine, high salinity waste streams. However, mineral scaling remains a major challenge when treating complex high-salt brines. The development of surface-patterned superhydrophobic membranes is one of the core strategies to solve this problem. We prepared flat sheet membranes (F-PVDF) and hydrophobic membranes with micron-scale corrugated pattern (C-PVDF) using a phase separation method. Their scaling behavior was systematically evaluated using calcium sulfate solutions and the impact of the feed flow was innovatively investigated. Although C-PVDF shows higher contact angle and lower sliding angle than F-PVDF, the scaling resistance of C-PVDF in the perpendicular flow direction has worst scaling resistance. Although the nucleation barrier of the corrugated membrane is the same at both parallel and perpendicular flow directions based on the traditional thermodynamic nucleation theory, experimental observations show that the C-PVDF has the best scaling resistance in the parallel flow direction. A 3D computational fluid dynamics (CFD) model was used and the hydrodynamic state of the pattern membranes was assessed as a determinant of the scaling resistance. The corrugated membrane with parallel flow mode (flow direction in parallel to the corrugation ridge) induces higher fluid velocity within the channel, which mitigated the deposition of crystals. While in the perpendicular flow mode (flow direction in perpendicular to the corrugation ridge), the solutions confined in the corrugated grooves due to vortex shielding, which aggravates the scaling. These results shed light on the mechanism of scaling resistance of corrugated membranes from a hydrodynamic perspective and reveal the mechanism of anisotropy exhibited by corrugated membranes in MD.

Single-cell microfluidics enabled dynamic evaluation of drug combinations on antibiotic resistance bacteria.

The rapid spread of antibiotic resistance has become a significant threat to global health, yet the development of new antibiotics is outpaced by emerging new resistance. To treat multidrug-resistant bacteria and prolong the lifetime of existing antibiotics, a productive strategy is to use combinations of antibiotics and/or adjuvants. However, evaluating drug combinations is primarily based on end-point checkerboard measurements, which provide limited information to study the mechanism of action and the discrepancies in the clinical outcomes. Here, single-cell microfluidics is used for rapid evaluation of the efficacy and mode of action of antibiotic combinations within 3 h. Focusing on multidrug-resistant Acinetobacter baumannii, the combination between berberine hydrochloride (BBH, as an adjuvant) and carbapenems (meropenem, MEM) or ß-lactam antibiotic is evaluated. Real-time tracking of individual cells to programmable delivered antibiotics reveals multiple phenotypes (i.e., susceptible, resistant, and persistent cells) with fidelity. Our study discovers that BBH facilitates the accumulation of antibiotics within cells, indicating synergistic effects (FICI = 0.5). For example, the combination of 256 mg/L BBH and 16 mg/L MEM has a similar killing effect (i.e., the inhibition rates >90%) as the MIC of MEM (64 mg/L). Importantly, the synergistic effect of a combination can diminish if the bacteria are pre-stressed with any single drug. Such information is vital for understanding the underlying mechanisms of combinational treatments. Overall, our platform provides a promising approach to evaluate the dynamic and heterogenous response of a bacterial population to antibiotics, which will facilitate new drug discovery and reduce emerging antibiotic resistance.

Ferromagnetic and half-metallic phase transition by doping in a one-dimensional narrow-bandgap W6PCl17 semiconductor.

Based on first-principles calculations, we predict a one-dimensional (1D) semiconductor with cluster-type structure, namely phosphorus-centered tungsten chloride W6PCl17. The corresponding single-chain system can be prepared from its bulk counterpart by an exfoliation method and it exhibits good thermal and dynamical stability. 1D single-chain W6PCl17 is a narrow direct semiconductor with a bandgap of 0.58 eV. The unique electronic structure endows single-chain W6PCl17 with the p-type transport characteristic, manifested as a large hole mobility of 801.53 cm2 V-1 s-1. Remarkably, our calculations show that electron doping can easily induce itinerant ferromagnetism in single-chain W6PCl17 due to the extremely flat band feature near the Fermi level. Such ferromagnetic phase transition expectedly occurs at an experimentally achievable doping concentration. Importantly, a saturated magnetic moment of 1µB per electron is obtained over a large range of doping concentrations (from 0.02 to 5 electrons per formula unit), accompanied by the stable existence of half-metallic characteristics. A detailed analysis of the doping electronic structures indicates that the doping magnetism is mainly contributed by the d orbitals of partial W atoms. Our findings demonstrate that single-chain W6PCl17 is a typical 1D electronic and spintronic material expected to be synthesized experimentally in the future.

Artificial intelligence-aided rapid and accurate identification of clinical fungal infections by single-cell Raman spectroscopy.

Integrating artificial intelligence and new diagnostic platforms into routine clinical microbiology laboratory procedures has grown increasingly intriguing, holding promises of reducing turnaround time and cost and maximizing efficiency. At least one billion people are suffering from fungal infections, leading to over 1.6 million mortality every year. Despite the increasing demand for fungal diagnosis, current approaches suffer from manual bias, long cultivation time (from days to months), and low sensitivity (only 50% produce positive fungal cultures). Delayed and inaccurate treatments consequently lead to higher hospital costs, mobility and mortality rates. Here, we developed single-cell Raman spectroscopy and artificial intelligence to achieve rapid identification of infectious fungi. The classification between fungi and bacteria infections was initially achieved with 100% sensitivity and specificity using single-cell Raman spectra (SCRS). Then, we constructed a Raman dataset from clinical fungal isolates obtained from 94 patients, consisting of 115,129 SCRS. By training a classification model with an optimized clinical feedback loop, just 5 cells per patient (acquisition time 2 s per cell) made the most accurate classification. This protocol has achieved 100% accuracies for fungal identification at the species level. This protocol was transformed to assessing clinical samples of urinary tract infection, obtaining the correct diagnosis from raw sample-to-result within 1 h.

A-to-I RNA Editing in Klebsiella pneumoniae Regulates Quorum Sensing and Affects Cell Growth and Virulence.

Millions of adenosine (A) to inosine (I) RNA editing events are reported and well-studied in eukaryotes; however, many features and functions remain unclear in prokaryotes. By combining PacBio Sequel, Illumina whole-genome sequencing, and RNA Sequencing data of two Klebsiella pneumoniae strains with different virulence, a total of 13 RNA editing events are identified. The RNA editing event of badR is focused, which shows a significant difference in editing levels in the two K. pneumoniae strains and is predicted to be a transcription factor. A hard-coded Cys is mutated on DNA to simulate the effect of complete editing of badR. Transcriptome analysis identifies the cellular quorum sensing (QS) pathway as the most dramatic change, demonstrating the dynamic regulation of RNA editing on badR related to coordinated collective behavior. Indeed, a significant difference in autoinducer 2 activity and cell growth is detected when the cells reach the stationary phase. Additionally, the mutant strain shows significantly lower virulence than the WT strain in the Galleria mellonella infection model. Furthermore, RNA editing regulation of badR is highly conserved across K. pneumoniae strains. Overall, this work provides new insights into posttranscriptional regulation in bacteria.

PPy/SWCNTs-Modified Microelectrode Array for Learning and Memory Model Construction through Electrical Stimulation and Detection of In Vitro Hippocampal Neuronal Network.

The learning and memory functions of the brain remain unclear, which are in urgent need for the detection of both a single cell signal with high spatiotemporal resolution and network activities with high throughput. Here, an in vitro microelectrode array (MEA) was fabricated and further modified with polypyrrole/carboxylated single-walled carbon nanotubes (PPy/SWCNTs) nanocomposites as the interface between biological and electronic systems. The deposition of the nanocomposites significantly improved the performance of microelectrodes including low impedance (60.3 ± 28.8 k Ω), small phase delay (-32.8 ± 4.4°), and good biocompatibility. Then the modified MEA was used to apply learning training and test on hippocampal neuronal network cultured for 21 days through electrical stimulation, and multichannel electrophysiological signals were recorded simultaneously. During the process of learning training, the stimulus/response ratio of the hippocampal learning population gradually increased and the response time gradually decreased. After training, the mean spikes in burst, number of bursts, and mean burst duration increased by 53%, 191%, and 52%, respectively, and the correlation of neurons in the network was significantly enhanced from 0.45 ± 0.002 to 0.78 ± 0.002. In addition, the neuronal network basically retained these characteristics for at least 5 h. These results indicated that we have successfully constructed a learning and memory model of hippocampal neurons on the in vitro MEA, contributing to understanding learning and memory based on synaptic plasticity. The proposed PPy/SWCNTs-modified in vitro MEA will provide a promising platform for the exploration of learning and memory mechanism and their applications in vitro.

Giant Enhancement of Raman Scattering by a Hollow-Core Microstructured Optical Fiber Allows Single Exosome Probing.

Microstructured optical fibers (MOFs) provide solutions for breaking through the bottlenecks in areas of high-power transmission and high-efficiency optical waveguides. Other than transporting light waves, MOFs can synergistically combine microfluidics and optics in a single fiber with an unprecedented light path length not readily achievable by planar optofluidic configurations. Here, we demonstrate that hollow-core anti-resonant optical fibers (HcARFs) can significantly enhance Raman scattering by over three orders of magnitude (EF ≈ 5000) compared with a planar setup, due to the joint mechanisms of strong light-matter interaction in the fiber core and the cumulative effect of the fiber. The giant enhancement enables us to develop the first optical fiber sensor to achieve single cancer exosome detection via a sandwich-structured strategy. This enables a multiplexed analysis of surface proteins of exosome samples, potentially allowing an accurate identification of the cellular origin of exosomes for cancer diagnosis. Our findings could expand the applications of HcARF in many exciting areas beyond the waveguide.

Two-Dimensional Violet Phosphorus P11: A Large Band Gap Phosphorus Allotrope.

The discovery of novel large band gap two-dimensional (2D) materials with good stability and high carrier mobility will innovate the next generation of electronics and optoelectronics. A new allotrope of 2D violet phosphorus P11 was synthesized via a salt flux method in the presence of bismuth. Millimeter-sized crystals of violet-P11 were collected after removing the salt flux with DI water. From single-crystal X-ray diffraction, the crystal structure of violet-P11 was determined to be in the monoclinic space group C2/c (no. 15) with unit cell parameters of a = 9.166(6) Å, b = 9.121(6) Å, c = 21.803(14)Å, ß = 97.638(17)°, and a unit cell volume of 1807(2) Å3. The structure differences between violet-P11, violet-P21, and fibrous-P21 are discussed. The violet-P11 crystals can be mechanically exfoliated down to a few layers (∼6 nm). Photoluminescence and Raman measurements reveal the thickness-dependent nature of violet-P11, and exfoliated violet-P11 flakes were stable in ambient air for at least 1 h, exhibiting moderate ambient stability. The bulk violet-P11 crystals exhibit excellent stability, being stable in ambient air for many days. The optical band gap of violet-P11 bulk crystals is 2.0(1) eV measured by UV-Vis and electron energy-loss spectroscopy measurements, in agreement with density functional theory calculations which predict that violet-P11 is a direct band gap semiconductor with band gaps of 1.8 and 1.9 eV for bulk and monolayer, respectively, and with a high carrier mobility. This band gap is the largest among the known single-element 2D layered bulk crystals and thus attractive for various optoelectronic devices.