Recent Progress on Stability and Passivation of Black Phosphorus

Emerging Low Detection Limit of Optically Activated Gas Sensors Based on 2D and Hybrid Nanostructures

Gas sensing is essential for detecting and measuring gas concentrations across various environments, with applications in environmental monitoring, industrial safety, and healthcare. The integration of two-dimensional (2D) materials, organic materials, and metal oxides has significantly advanced gas sensor technology, enhancing its sensitivity, selectivity, and response times at room temperature. This review examines the progress in optically activated gas sensors, with emphasis on 2D materials, metal oxides, and organic materials, due to limited studies on their use in optically activated gas sensors, in contrast to other traditional gas-sensing technologies. We detail the unique properties of these materials and their impact on improving the figures of merit (FoMs) of gas sensors. Transition metal dichalcogenides (TMDCs), with their high surface-to-volume ratio and tunable band gap, show exceptional performance in gas detection, especially when activated by UV light. Graphene-based sensors also demonstrate high sensitivity and low detection limits, making them suitable for various applications. Although organic materials and hybrid structures, such as metal-organic frameworks (MoFs) and conducting polymers, face challenges related to stability and sensitivity at room temperature, they hold potential for future advancements. Optically activated gas sensors incorporating metal oxides benefit from photoactive nanomaterials and UV irradiation, further enhancing their performance. This review highlights the potential of the advanced materials in developing the next generation of gas sensors, addressing current research gaps and paving the way for future innovations.

Surface Engineering of Two-Dimensional Black Phosphorus for Advanced Nanophotonics

ConspectusEverything in the world has two sides. We should correctly understand its two sides to pursue the positive side and get rid of the negative side. Recently, two-dimensional (2D) black phosphorus (BP) has received a tremendous amount of attention and has been applied for broad applications in optoelectronics, transistors, logic devices, and biomedicines due to its intrinsic properties, e.g., thickness-dependent bandgap, high mobility, highly anisotropic charge transport, and excellent biodegradability and biocompatibility. On one hand, rapid degradation of 2D BP under ambient conditions becomes a vital bottleneck that largely hampers its practical applications in optical and optoelectronic devices and photocatalysis. On the other hand, just because of its ambient instability, 2D BP as a novel kind of nanomedicine in a cancer drug delivery system can not only satisfy effective cancer therapy but also enable its safe biodegradation in vivo. Until now, a variety of surface functionality types and approaches have been employed to rationally modify 2D BP to meet the growing requirements of advanced nanophotonics.In this Account, we describe our research on surface engineering of 2D BP in two opposite ways: (i) stabilizing 2D BP by various approaches for advanced nanophotonic devices with both remarkable photoresponse behavior and environmentally structural stability and (ii) making full use of biodegradation, biocompatibility, and biological activity (e.g., photothermal therapy, photodynamic therapy, and bioimaging) of 2D BP for the construction of high-performance delivery nanoplatforms for biophotonic applications. We highlight the targeted aims of the surface-engineered 2D BP for advanced nanophotonics, including photonic devices (optics, optoelectronics, and photocatalysis) and photoinduced cancer therapy, by means of various surface functionalities, such as heteroatom incorporation, polymer functionalization, coating, heterostructure design, etc. From the viewpoint of potential applications, the fundamental properties of surface-engineered 2D BP and recent advances in surface-engineered 2D BP-based nanophotonic devices are briefly discussed. For the photonic devices, surface-engineered 2D BP can not only effectively improve environmentally structural stability but also simultaneously maintain photoresponse performance, enabling 2D BP-based devices for a wide range of practical applications. In terms of the photoinduced cancer therapy, surface-engineered 2D BP is more appropriate for the treatment of cancer due to negligible toxicity and excellent biodegradation and biocompatibility. We also provide our perspectives on future opportunities and challenges in this important and fast-growing field. It is envisioned that this Account can attract more attention in this area and inspire more scientists in a variety of research communities to accelerate the development of 2D BP for more widespread high-performance nanophotonic applications.

Current advances in black phosphorus-based antibacterial nanoplatform for infection therpy

Black phosphorus (BP) has attracted much attention due to its excellent physiochemical properties. However, due to its biodegradability and simple antibacterial mechanism, using only BP nanomaterials to combat bacterial infections caused by drug-resistant pathogens remains a significant challenge. In order to improve the antibacterial efficiency and avoid the emergence of drug resistance, BP nanomaterials have been combined with other functional materials to form black phosphorus-based antibacterial nanoplatform (BPANP), which provides unprecedented opportunities for the treatment of drug-resistant infections. This article reviews the performance of BPANP and its multiple antibacterial mechanisms while emphatically introducing its design direction and latest application progress in antibacterial fields. Moreover, this paper additionally summarizes and discusses the current challenges and inadequacies of BPANP that need to be improved in future research. We believe that this review will provide researchers with an up-to-date and multifaceted reference, and provide new ideas for designing effective strategies against drug-resistant bacteria.

A Flexible MXene-Black Phosphorus/Zinc Oxide Hybrid Structure with Excellent UVA-Specific Photoelectric Sensing Properties for Human Skin Protection

Ultraviolet A (UVA) radiation causes various irreversible damages to human skin, so the research about UVA-specific sensing device is urgent. 2D black phosphorus (BP) is used in many photosensors due to its advantages of high carrier mobility and tunable bandgap, but its application for UVA-specific photosensor is not reported. Here, a MXene-BP/Zinc oxide (ZnO) hybrid structure with lamellar-spherical interfaces like finger lime fruit is prepared by the layer-by-layer assembly (LLA) method, and p-n junctions are constructed between BP and ZnO with the Ti3C2Tx electrode, showing excellent photoelectric performance. Density functional theory (DFT) calculations demonstrate that the enhanced performance is attributed to the rapid separation of photogenerated carriers in the presence of a built-in electric field at interface. Furthermore, a flexible MXene-BP/ZnO based UVA-specific photosensor is prepared, which shows a specific response to UVA as high as 7 mA W-1 and excellent mechanical stability, maintaining 98.46% response after 100 bending cycles. In particular, the integrated anti-UVA skin protection device shows excellent UVA-specific identification and wireless transmission capability, which can provide timely UVA exposure information and skin protection warning for the visually impaired. This work demonstrates a new approach for further developments of advanced photoelectric sensing technology toward improving people's skin health protection.

AuNPs-BP-MWCNTs-COOH-based electrochemical immunosensor for the determination of deoxynivalenol in wheat flour

Deoxynivalenol (DON) has drawn considerable attention for its obvious pathogenicity and wide use in agro-products, which cause a potential threat to human health. In this work, an electrochemical immunosensor is developed for the highly sensitive and selective detection of DON in wheat flour using AuNPs-BP-MWCNTs-COOH and antibodies. The AuNPs-BP-MWCNTs-COOH nanocomposite was prepared via an in situ reduction reaction and ultrasonic-assisted liquid-phase exfoliation. The nanocomposite exhibits a larger surface area, decent stability, excellent electron transfer capability, good protein binding capability and prominent specificity. The plentiful carboxyl group on the nanocomposite can bind to the amino group of the antibody, and AuNPs have an affinity for the sulfhydryl group of the antibody, which makes it feasible for the nanocomposite to load the antibody. The peak currents are plotted against the logarithm of DON concentration from 0.002 to 80 ng mL-1 with a limit of detection (LOD) of 0.5 pg mL-1. This approach establishes an effective label-free immunosensor platform for the detection of DON with high sensitivity and selectivity in various food and agricultural products.

Van der Waals Encapsulation by Ultrathin Oxide for Air-Sensitive 2D Materials

The ambient stability is one of the focal points for applications of 2D materials, especially for those well-known air-sensitive ones, such as black phosphorus (BP) and transitional metal telluride. Traditional methods of encapsulation, such as atomic layer deposition of oxides and heterogeneous integration of hexagonal boron nitride, can hardly avoid removal of encapsulation layer when the 2D materials are encapsulated for further device fabrication, which causes complexity and damage during the procedure. Here, a van der Waals encapsulation method that allows direct device fabrication without removal of encapsulation layer is introduced using Ga2O3 from liquid gallium. Taking advantage of the robust isolation ability against ambient environment of the dense native oxide of gallium, hundreds of times longer retention time of (opto)electronic properties of encapsulated BP and MoTe2 devices is realized than unencapsulated devices. Due to the ultrathin high-κ properties of Ga2O3, top-gated devices are directly fabricated with the encapsulation layer, simultaneously as a dielectric layer. This direct device fabrication is realized by selective etching of Ga2O3, leaving the encapsulated materials intact. Encapsulated 1T' MoTe2 exhibits high conductivity even after 150 days in ambient environment. This method is, therefore, highlighted as a promising and distinctive one compared with traditional passivation approaches.

Tribology of 2D black phosphorus - Current state-of-the-art and future potential

Since the first mechanical exfoliation of graphene in 2004, the interest in 2D materials has significantly risen due to their outstanding property combination. Multiple 2D materials have been synthesized until today, while black phosphorus (BP) resembles one of their latest additions. The unique properties of BP, especially for electronic and optical devices (i.e., high carrier mobility and electrical conduction, field-effect transistor, layer-dependent bandgap, anisotropic transport), have gained notable attention. However, its layered structure, similar to those of graphene and MoS2, is also advantageous to optimize the friction and wear performance. Moreover, the strong in-plane covalent bonds and weak interlayer van-der-Waals forces favour the formation of low-friction and wear-resistant films. Although BP holds a great tribological potential, the literature to date on this topic is rather scarce. Therefore, it is a timely moment to holistically summarize the synthesis approaches and properties of BP thus guiding interested researchers to use it in mechanical/tribological applications. The existing state-of-the-art regarding tribological research is critically discussed and compared to other 2D materials thus highlighting existing research gaps and paving the way for future research activities.

Innovative Biomaterials for Bone Tumor Treatment and Regeneration: Tackling Postoperative Challenges and Charting the Path Forward

Surgical resection of bone tumors is the primary approach employed in the treatment of bone cancer. Simultaneously, perioperative interventions, particularly postoperative adjuvant anticancer strategies, play a crucial role in achieving satisfactory therapeutic outcomes. However, the occurrence of postoperative bone tumor recurrence, metastasis, extensive bone defects, and infection are significant risks that can result in unfavorable prognoses or even treatment failure. In recent years, there has been significant progress in the development of biomaterials, leading to the emergence of new treatment options for bone tumor therapy and bone regeneration. This progress report aims to comprehensively analyze the strategic development of unique therapeutic biomaterials with inherent healing properties and bioactive capabilities for bone tissue regeneration. These composite biomaterials, classified into metallic, inorganic non-metallic, and organic types, are thoroughly investigated for their responses to external stimuli such as light or magnetic fields, internal interventions including chemotherapy or catalytic therapy, and combination therapy, as well as their role in bone regeneration. Additionally, an overview of self-healing materials for osteogenesis is provided and their potential applications in combating osteosarcoma and promoting bone formation are explored. Furthermore, the safety concerns of integrated materials and current limitations are addressed, while also discussing the challenges and future prospects.

Regulation of band gap and localized surface plasmon resonance by loading Au nanorods on violet phosphene nanosheets for photodynamic/photothermal synergistic anti-infective therapy

In the face of the serious threat to human health and the economic burden caused by bacterial antibiotic resistance, 2D phosphorus nanomaterials have been widely used as antibacterial agents. Violet phosphorus nanosheets (VPNSs) are an exciting bandgap-adjustable 2D nanomaterial due to their good physicochemical properties, yet the study of VPNS-based antibiotics is still in its infancy. Here, a composite of gold nanorods (AuNRs) loaded onto VPNS platforms (VPNS/AuNR) is constructed to maximize the potential of VPNSs for antimicrobial applications. The loading with AuNRs not only enhances the photothermal performance via a localized surface plasmon resonance (LSPR) effect, but also enhances the light absorption capacity due to the narrowing of the band gap of the VPNSs, thus increasing the ROS generation capacity. The results demonstrate that VPNS/AuNR exhibits outstanding antibacterial properties and good biocompatibility. Attractively, VPNS/AuNR is then extensively tested for treating skin wound infections, suggesting promising in vivo antibacterial and wound-healing features. Our findings may open a novel direction to develop a versatile VPNS-based treatment platform, which can significantly boost the progress of VPNS exploration.

Recent advances in ambient-stable black phosphorus materials for artificial catalytic nitrogen cycle in environment and energy

Nitrogen cycle is crucial for the Earth's ecosystem and human-nature coexistence. However, excessive fertilizer use and industrial contamination disrupt this balance. Semiconductor-based artificial nitrogen cycle strategies are being actively researched to address this issue. Black phosphorus (BP) exhibits remarkable performance and significant potential in this area due to its unique physical and chemical properties. Nevertheless, its practical application is hindered by ambient instability. This review covers the synthesis methods of BP materials, analyzes their instability factors under environmental conditions, discusses stability improvement strategies, and provides an overview of the applications of ambient-stable BP materials in nitrogen cycle, including N2 fixation, NO3- reduction, NOx removal and nitrides sensing. The review concludes by summarizing the challenges and prospects of BP materials in the nitrogen cycle, offering valuable guidance to researchers.

Adsorption Behavior of NO and NO2 on Two-Dimensional As, Sb, and Bi Materials: First-Principles Insights

To address the most significant environmental challenges, the quest for high-performance gas sensing materials is crucial. Among numerous two-dimensional materials, this study investigates the gas-sensitive capabilities of monolayer As, Sb, and Bi materials. To compare the gas detection abilities of these three materials, we employ first-principles calculations to comprehensively study the adsorption behavior of NO and NO2 gas molecules on the material surfaces. The results indicate that monolayer Bi material exhibits reasonable adsorption distances, substantial adsorption energies, and significant charge transfer for both NO and NO2 gases. Therefore, among the materials studied, it demonstrates the best gas detection capability. Furthermore, monolayer As and Sb materials exhibit remarkably high capacities for adsorbing NO and NO2 gas molecules, firmly interacting with the gas molecules. Gas adsorption induces changes in the material's work function, suggesting the potential application of these two materials as catalysts.

Hydrolysis of Solid Buffer Enables High-Performance Aqueous Zinc Ion Battery

Aqueous zinc (Zn) ion batteries (AZIBs) have not yet fulfilled their talent of high safety and low cost since the anode/electrolyte interface (AEI) has long been impeded by hydrogen evolution, surface corrosion, dendritic growth, and by-product accumulation. Here, the hydrolysis of solid buffers is elaborately proposed to comprehensively and enduringly handle these issues. Take 2D layered black phosphorus (BP) as a hydrolytic subject. It is reported that the phosphoric acid generated by hydrolysis in an aqueous electrolyte produces a zinc phosphate (ZPO) rich solid electrolyte interphase (SEI) layer, which largely inhibits the dendrite growth, surface corrosion, and hydrogen evolution. Meanwhile, the hydrolytic phosphoric acid stabilizes the pH value near AEI, avoiding the accumulation of alkaline by-products. Notably, compared with the disposable ZPO engineerings of anodic SEI pre-construction and electrolyte additive, the hydrolysis strategy of BP can realize a dramatically prolonged protective effect. As a result, these multiple merits endow BP modified separator to achieve improved stripping/plating stability toward Zn anode with more than ten times lifespan enhancement in Zn||Zn symmetrical cell. More encouragingly, when coupled with a V2 O5 ·nH2 O cathode with ultra-high loadings (34.1 and 28.7 mg cm-2 ), the cumulative capacities are remarkably promoted for both coin and pouch cells.

Novel RNA genosensor based on highly stable gold nanoparticles decorated phosphorene nanohybrid with graphene for highly sensitive and low-cost electrochemical detection of coconut cadang-cadang viroid

Coconut cadang-cadang viroid (CCCVd) is an infectious single-stranded RNA (ssRNA) pathogen, which leads directly to the death of a large number of coconut palm trees and heavy economic loss to coconut farmers. Herein, a novel electrochemical impedance RNA genosensor is presented based on highly stable gold nanoparticles (AuNPs) decorated phosphorene (BP) nanohybrid with graphene (Gr) for highly sensitive, low-cost, and label-free detection of CCCVd. BP-AuNPs are environmentally friendly prepared by ultrasonic-assisted liquid-phase exfoliation of black phosphorus, accompanying direct reduction of chloroauric acid. Gr/BP-AuNPs are facilely prepared by the in situ growth of AuNPs onto the BP surface and its nanohybrid with Gr to improve environmental stability of BP. Gr/BP-AuNP-based RNA genosensor is fabricated by immobilizing the thiol-functionalized single-stranded DNA (ssDNA) oligonucleotide probe onto the surface of Gr/BP-AuNP-modified glassy carbon electrode via gold-thiol interactions, which served as an electrochemical genosensing platform for the label-free impedance detection of CCCVd by hybridization between the functionalized ssDNA probe and the complementary CCCVd ssRNA sequence in a wide linear range from 1.0 × 10-11 to 1.0 × 10-7 M with a low limit of detection of 2.8 × 10-12 M. This work supplies an experimental support and theoretical direction for the fabrication of RNA biosensors based on graphene-like materials and potential application for a specific diagnosis of plant RNA viral disease in Arecaceae planting industry.

Landauer-QFLPS Model for Mixed Schottky-Ohmic Contact Two-Dimensional Transistors

Two-dimensional material-based field-effect transistors (2DM-FETs) are playing a revolutionary role in electronic devices. However, before electronic design automation (EDA) for 2DM-FETs can be achieved, it remains necessary to determine how to incorporate contact transports into model. Reported methods compromise between physical intelligibility and model compactness due to the heterojunction nature. To address this, quasi-Fermi-level phase space theory (QFLPS) is generalized to incorporate contact transports using the Landauer formula. It turns out that the Landauer-QFLPS model effectively overcomes the issue of concern. The proposed new formula can describe 2DM-FETs with Schottky or Ohmic contacts with superior accuracy and efficiency over previous methods, especially when describing non-monotonic drain conductance characteristics. A three-bit threshold inverter quantizer (TIQ) circuit is fabricated using ambipolar black phosphorus and it is demonstrated that the model accurately predicts circuit performance. The model could be very effective and valuable in the development of 2DM-FET-based integrated circuits.

Two-dimensional nanomaterials as enhanced surface plasmon resonance sensing platforms: Design perspectives and illustrative applications

Both increasing demand for ultrasensitive detection in the scientific community and significant new breakthroughs in materials science field have inspired and promoted the development of new-generation multifunctional plasmonic sensing platforms by adopting promising plasmonic nanomaterials. Recently, high-quality surface plasmon resonance (SPR) sensors, assisted by two dimensional (2D) nanomaterials including 2D van der Waals (vdWs) materials (such as graphene/graphene oxide, transition metal dichalcogenides (TMDs), phosphorene, antimonene, tellurene, MXenes, and metal oxides), 2D metal-organic frameworks (MOFs), 2D hyperbolic metamaterials (HMMs), and 2D optical metasurfaces, have emerged as a class of novel plasmonic sensing platforms that show unprecedented detection sensitivity and impressive performance. This review of recent progress in 2D nanomaterials-enhanced SPR platforms will highlight their compelling plasmonic enhancement features, working mechanisms, and design methodologies, as well as discuss illustrative practical applications. Hence, it is of great importance to describe the latest research progress in 2D nanomaterials-enhanced SPR sensing cases. In this review, we present some concepts of SPR enhanced by 2D nanomaterials, including the basic principles of SPR, signal modulation approaches, and working enhancement mechanisms for various 2D materials-enhanced SPR systems. In addition, we also demonstrate a detailed categorization of 2D nanomaterials-enhanced SPR sensing platforms and comment on their ability to realize ultrasensitive SPR detection. Finally, we conclude with future perspectives for exploring a new generation of 2D nanomaterials-based sensors.

Black Phosphorus Molybdenum Disulfide Midwave Infrared Photodiodes with Broadband Absorption-Increasing Metasurfaces

Black phosphorus (BP) has been established as a promising material for room temperature midwave infrared (MWIR) photodetectors. However, many of its attractive optoelectronic properties are often observable only at smaller film thicknesses, which inhibits photodetector absorption and performance. In this work, we show that metasurface gratings increase the absorption of BP-MoS2 heterojunction photodiodes over a broad range of wavelengths in the MWIR. We designed, fabricated, and characterized metasurface gratings that increase absorption at selected wavelengths or broad spectral ranges. We evaluated the broadband metasurfaces by measuring the room temperature responsivity and specific detectivity of BP-MoS2 photodiodes at multiple MWIR wavelengths. Our results show that broadband metasurface gratings are a scalable approach for boosting the performance of BP photodiodes over large spectral ranges.

Nitrogen doped CoP on ammoniated black phosphorus nanosheets enabling highly efficient hydrogen evolution electrocatalysis

Developing a rational and cost-effective approach for designing highly-efficient and sustainable electrocatalysts is essential for clean and renewable hydrogen energy. Herein, we report nitrogen-doped CoP on two-dimensional ammoniated black phosphorus (BP) nanosheets (N-CoP/NH2-BP) as novel and highly-active heterostructure electrocatalysts for the hydrogen evolution reaction (HER). Using the reactive defects on the BP nanosheets as the original sites under NH3 gas, N-doped CoP nanocrystals were grown on the surface of the BP nanosheets that were functionalized with NH2 groups at their edge. The N-CoP/NH2-BP heterostructure exhibits low overpotentials of 90 and 246 mV at 10 and 200 mA cm-2, respectively, in an alkaline electrolyte. The excellent HER activity should be attributed to the synergistic effect between N-doped CoP and NH2-functionalized BP, in which NH2-BP, with its high electron mobility and hydrophilicity, accelerates the charge transfer and offers more active sites, moreover, N-doped CoP modulates the electronic structure of CoP for enhanced HER activity. This work not only provides a novel and effective electrocatalyst, but also opens up a straightforward strategy for the design of phosphorene-based electrocatalysts for highly efficient hydrogen evolution and beyond.

Recent Developments of Inorganic Nanosensitizers for Sonodynamic Therapy

As a noninvasive treatment, sonodynamic therapy (SDT) has been widely used in the treatment of tumors because of its ability to penetrate deep tissue with few side effects. As the key factor of SDT, it is meaningful to design and synthesize efficient sonosensitizers. Compared with organic sonosensitizers, inorganic sonosensitizers can be easily excited by ultrasound. In addition, inorganic sonosensitizers with stable properties, good dispersion, and long blood circulation time, have great development potential in SDT. This review summarizes possible mechanisms of SDT (sonoexcitation and ultrasonic cavitation) in detail. Based on these mechanisms, the design and synthesis of inorganic nanosonosensitizers can be divided into three categories: traditional inorganic semiconductor sonosensitizers, enhanced inorganic semiconductor sonosensitizers, and cavitation-enhanced sonosensitizers. Subsequently, the current efficient construction methods of sonosensitizers are summarized including accelerated semiconductor charge separation and enhanced production of reactive oxygen species through ultrasonic cavitation. Furthermore, the advantages and disadvantages of different inorganic sonosensitizers and detailed strategies are systematically discussed on how to enhance SDT. Hopefully, this review could provide new insights into the design and synthesis of efficient inorganic nano-sonosensitizers for SDT.

Transferred Polymer-Encapsulated Metal Electrodes for Electrical Transport Measurements on Ultrathin Air-Sensitive Crystals

Owing to rapid property degradation after ambient exposure and incompatibility with conventional device fabrication process, electrical transport measurements on air-sensitive 2D materials have always been a big issue. Here, for the first time, a facile one-step polymer-encapsulated electrode transfer (PEET) method applicable for fragile 2D materials is developed, which showed great advantages of damage-free electrodes patterning and in situ polymer encapsulation preventing from H2 O/O2 exposure during the whole electrical measurements process. The ultrathin SmTe2 metals grown by chemical vapor deposition (CVD) are chosen as the prototypical air-sensitive 2D crystals for their poor air-stability, which will become highly insulating when fabricated by conventional lithographic techniques. Nevertheless, the intrinsic electrical properties of CVD-grown SmTe2 nanosheets can be readily investigated by the PEET method instead, showing ultralow contact resistance and high signal/noise ratio. The PEET method can be applicable to other fragile ultrathin magnetic materials, such as (Mn,Cr)Te, to investigate their intrinsic electrical/magnetic properties.

Electrochemical Biosensor Based on Horseradish Peroxidase and Black Phosphorene Quantum Dot Modified Electrode

Black phosphorene quantum dots (BPQDs) were prepared by ultrasonic-assisted liquid-phase exfoliation and centrifugation with morphologies proved by TEM results. Furthermore, an electrochemical enzyme sensor was prepared by co-modification of BPQDs with horseradish peroxidase (HRP) on the surface of a carbon ionic liquid electrode (CILE) for the first time. The direct electrochemical behavior of HRP was studied with a pair of well-shaped voltammetric peaks that appeared, indicating that the existence of BPQDs was beneficial to accelerate the electron transfer rate between HRP and the electrode surface. This was due to the excellent properties of BPQDs, such as small particle size, high interfacial reaction activity, fast conductivity, and good biocompatibility. The presence of BPQDs on the electrode surface provided a fast channel for direct electron transfer of HRP. Therefore, the constructed electrochemical HRP biosensor was firstly used to investigate the electrocatalytic behavior of trichloroacetic acid (TCA) and potassium bromate (KBrO3), and the wide linear detection ranges of TCA and KBrO3 were 4.0-600.0 mmol/L and 2.0-57.0 mmol/L, respectively. The modified electrode was applied to the actual samples detection with satisfactory results.

Black Phosphorus for Photonic Integrated Circuits

Black phosphorus gives several advantages and complementarities over other two-dimensional materials. It has drawn extensive interest owing to its relatively high carrier mobility, wide tunable bandgap, and in-plane anisotropy in recent years. This manuscript briefly reviews the structure and physical properties of black phosphorus and targets on black phosphorus for photonic integrated circuits. Some of the applications are discussed including photodetection, optical modulation, light emission, and polarization conversion. Corresponding recent progresses, associated challenges, and future potentials are covered.

2D Layered Materials for Fast-Charging Lithium-Ion Battery Anodes

The development of electric vehicles has received worldwide attention in the background of reducing carbon emissions, wherein lithium-ion batteries (LIBs) become the primary energy supply systems. However, commercial graphite-based anodes in LIBs currently confront significant difficulty in enduring ultrahigh power input due to the slow Li+ transport rate and the low intercalation potential. This will, in turn, cause dramatic capacity decay and lithium plating. The 2D layered materials (2DLMs) recently emerge as new fast-charging anodes and hold huge promise for resolving the problems owing to the synergistic effect of a lower Li+ diffusion barrier, a proper Li+ intercalation potential, and a higher theoretical specific capacity with using them. In this review, the background and fundamentals of fast-charging for LIBs are first introduced. Then the research progress recently made for 2DLMs used for fast-charging anodes are elaborated and discussed. Some emerging research directions in this field with a short outlook on future studies are further discussed.

Modulating the Function of GeAs/ReS2 van der Waals Heterojunction with its Potential Application for Short-Wave Infrared and Polarization-Sensitive Photodetection

Van der Waals heterojunction (vdWs) of 2D materials with integrated or extended superior characteristics, opening up new opportunities in functional electronic and optoelectric device applications. Exploring methods to achieve multifunctional vdWs heterojunction devices is one of the most promising prospects in this area. Herein, a diverse function of forward rectifying diode, Zener tunneling diode, and backward rectifying diodes are realized in GeAs/ReS2 heterojunction by modulating the doping level of GeAs. The tunneling diode presents an interesting trend forward negative differential resistance (NDR) behavior which may facilitate the application of multi-value logic. More importantly, the GeAs/ReS2 forward rectifying diode exhibits highly sensitive photodetection in the wide-spectrum range up to 1550 nm corresponding to a short-wave infrared (SWIR) region. In addition, as two strong anisotropic 2D materials of GeAs and ReS2 , the heterojunction exhibits strong polarization-sensitive photodetection behavior with a dichroic photocurrent ratio of 1.7. This work provides an effective strategy to achieve multifunctional 2D vdW heterojunction devices and develops more possibilities to broaden their functionalities and applications.

Electronic Structure of Few-Layer Black Phosphorus from μ-ARPES

Black phosphorus (BP) stands out among two-dimensional (2D) semiconductors because of its high mobility and thickness dependent direct band gap. However, the quasiparticle band structure of ultrathin BP has remained inaccessible to experiment thus far. Here we use a recently developed laser-based microfocus angle resolved photoemission (μ-ARPES) system to establish the electronic structure of 2-9 layer BP from experiment. Our measurements unveil ladders of anisotropic, quantized subbands at energies that deviate from the scaling observed in conventional semiconductor quantum wells. We quantify the anisotropy of the effective masses and determine universal tight-binding parameters, which provide an accurate description of the electronic structure for all thicknesses.

Observation of optical anisotropy and a linear dichroism transition in layered silicon phosphide

The investigation of in-plane two-dimensional (2D) anisotropic materials has garnered significant attention due to their exceptional electronic, optical, and mechanical characteristics. The anisotropic optical properties and angle-dependent photodetectors based on 2D anisotropic materials have been extensively studied. However, novel in-plane anisotropic materials still need to be explored to satisfy for distinct environments and devices. Here, we report the remarkable anisotropic behavior of excitons and demonstrate a unique linear-dichroism transition of absorption between ultraviolet and visible light in layered silicon phosphide (SiP) through the analysis of polarization photoluminescence (PL) and absorbance spectra. Its high absorption linear dichroism ratio of 1.16 at 388 nm, 1.15 at 532 nm, and 1.19 at 733 nm is revealed, suggesting the brilliant non-isotropic responses. The robust periodic variation of the A₁ and A₂ Raman modes in 2D SiP materials allows for the determination of their crystal orientation. Furthermore, the presence of indirect excitons with phonon sidebands in the temperature-dependent PL spectra exhibits non-monotonic energy shifts with increasing temperature, which is attributed to an enhanced electron-phonon interaction and thermal expansion. Our findings provide valuable insights into the fundamental physical properties of layered SiP and offer guidelines for designing polarization-sensitive photodetectors and angle-dependent devices based on 2D anisotropic materials.

Oxidation kinetics and non-Marcusian charge transfer in dimensionally confined semiconductors

Electrochemical reactions represent essential processes in fundamental chemistry that foster a wide range of applications. Although most electrochemical reactions in bulk substances can be well described by the classical Marcus-Gerischer charge transfer theory, the realistic reaction character and mechanism in dimensionally confined systems remain unknown. Here, we report the multiparametric survey on the kinetics of lateral photooxidation in structurally identical WS₂ and MoS₂ monolayers, where electrochemical oxidation occurs at the atomically thin monolayer edges. The oxidation rate is correlated quantitatively with various crystallographic and environmental parameters, including the density of reactive sites, humidity, temperature, and illumination fluence. In particular, we observe distinctive reaction barriers of 1.4 and 0.9 eV for the two structurally identical semiconductors and uncover an unusual non-Marcusian charge transfer mechanism in these dimensionally confined monolayers due to the limit in reactant supplies. A scenario of band bending is proposed to explain the discrepancy in reaction barriers. These results add important knowledge into the fundamental electrochemical reaction theory in low-dimensional systems.

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, β = 97.638(17)°, and a unit cell volume of 1807(2) ų. 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.

Effective Passivation of Anisotropic 2D GeAs via Graphene Encapsulation for Highly Stable Near-Infrared Photodetectors

Germanium arsenic (GeAs) as a promising two-dimensional (2D) semiconducting material has attracted extensive attention. The high carrier mobility and tunable bandgap of GeAs offer broad prospects in electronic and optoelectronic device-related applications. The unique intrinsic anisotropy arising from the low-symmetry structure can be applied in the design of new devices. However, the rapid degradation of mechanically exfoliated GeAs in the environment poses a challenge to its practical development in scalable devices. Here, an approach to stabilize the sensitive material without isolation from the ambient environment is reported. The graphene capping layer effectively suppresses environmental degradation, enabling the encapsulated GeAs photodetectors to maintain the key electronic properties for more than 3 months under ambient conditions. In addition, the regulation of the work function of graphene significantly improves the device performance. An improved responsivity of 965.07 A/W is 20 times higher than that of pure GeAs. This work provides opportunities for the practical application of GeAs and other environmentally sensitive 2D materials.

Degradation Studies of Air-Exposed Black Phosphorous and Black Arsenic Phosphorous

This work investigates the effects of oxygen and humidity on black phosphorous (BP) and black arsenic phosphorous (AsxP1−x ) flakes using Raman spectroscopy and in situ electric transport measurements (four-probe resistance and thermoelectric power, TEP). The results show that the incorporation of arsenic into the lattice of BP renders it more stable, with the degradation times for BP, As0.2P0.8, and As0.4P0.6 being 4, 5, and 11 days, respectively. The P-P Raman peak intensities were determined to decrease with exposure to oxygen and moisture. The TEP measurements confirmed that both BP and AsxP1−x are p-type semiconductors with the TEP of As0.4P0.6 stabilizing more slowly than that of BP. In addition, the four-probe resistance of BP and AsxP1−x stabilized significantly faster when exposed to air after being degassed in a vacuum. This was attributed to the charge transfer between the oxygen redox potential of air and the Fermi energy (EF) of the semiconductors.

Investigation of adsorption behaviors, and electronic and magnetic properties for small gas molecules adsorbed on Pt-doped arsenene by density functional calculations

Based on first-principles calculations, we compared the adsorption behaviors, electronic and magnetic properties of gas molecules (CO, NO, NO2, O2, NH3, H2O, H2 and N2) adsorbed on Pt-embedded arsenene and pristine arsenene. Our calculations show the interactions between molecules and arsenene can be enhanced by substitution of a Pt atom, suggesting the potential application of Pt-doped arsenene in gas sensing, especially for detecting NO2 gas due to the largest adsorption energy and charge transfer between NH3 and Pt-doped arsenene. Among all the molecules considered, CO, NO, NO2, O2 and NH3 molecules chemisorb on Pt-doped arsenene (these molecules physisorb on pristine arsenene) forming covalent Pt-C, Pt-N and Pt-O bonds, thus resulting in the elongation of C-O, N-O, O-O, N-H bonds in molecules. The magnetic moments of arsenene adsorbed with O2, NO, and NO2 decrease or diminish after Pt doping. Such variation on magnetism before and after Pt doping is ascribed to significant charge transfer and strong hybridization between gas molecules and the underlying Pt atoms, indicating the magnetic properties of arsenene can be tuned by molecular adsorption and Pt doping. These findings suggest Pt-doped arsenene has potential applications in spintronic devices, catalysts and gas sensors.

Chirality-Dependent Tumor Phototherapy Using Amino Acid-Engineered Chiral Phosphorene

Phosphorene, also known as black phosphorus nanosheet (BPNS), has been investigated as a nanoagent for tumor therapy. However, promoting its intracellular accumulation while preventing the cytoplasmic decomposition remains challenging. Herein, for the first time, we propose a chiral BPNS designed through surface engineering based on amino acids with high biocompatibility and an abundant source for application in chirality-dependent tumor phototherapy based on its intracellular metabolism. The advantage of using cysteine (Cys) over other amino acids was that its d, l, or dl-form could efficiently work as the chirality inducer to modify the BPNS through electrostatic interaction and prevent alterations in the intrinsic properties of the BPNS. In particular, d-Cys-BPNS displayed an approximately threefold cytotoxic effect on tumor cells compared with l-Cys-BPNS, demonstrating a chirality-dependent therapy behavior. d-Cys-BPNS not only promoted high intracellular content but also showed resistance to cytoplasmic decomposition. Cys-engineered BPNS also demonstrated chirality-dependent phototherapy effects on tumor-bearing mice, in proximity to the results in vitro. Chiral engineering is expected to open new avenues that could promote the use of BPNS in tumor phototherapy and boost chiral nanomedicine.

2D Materials-Based Static Random-Access Memory

2D transition-metal dichalcogenide semiconductors, such as MoS₂ and WSe₂ , with adequate bandgaps are promising channel materials for ultrascaled logic transistors. This scalability study of 2D material (2DM)-based field-effect transistor (FET) and static random-access memory (SRAM) cells analyzing the impact of layer thickness reveals that the monolayer 2DM FET with superior electrostatics is beneficial for its ability to mitigate the read-write conflict in an SRAM cell at scaled technology nodes (1-2.1 nm). Moreover, the monolayer 2DM SRAM exhibits lower cell read access time and write time than the bilayer and trilayer 2DM SRAM cells at fixed leakage power. This simulation predicts that the optimization of 2DM SRAM designed with state-of-the-art contact resistance, mobility, and equivalent oxide thickness leads to excellent stability and operation speed at the 1-nm node. Applying the nanosheet (NS) gate-all-around (GAA) structure to 2DM further reduces cell read access time and write time and improves the area density of the SRAM cells, demonstrating a feasible scaling path beyond Si technology using 2DM NSFETs. In addition to the device design, the process challenges for 2DM NSFETs, including the cost-effective stacking of 2DM layers, formation of electrical contacts, suspended 2DM channels, and GAA structures, are also discussed.

Resonant Grating-Enhanced Black Phosphorus Mid-Wave Infrared Photodetector

Black phosphorus (BP) has emerged as a promising materials system for mid-wave infrared photodetection because of its moderate bandgap, high carrier mobility, substrate compatibility, and bandgap tunability. However, its uniquely tunable bandgap can only be taken advantage of with thin layer thicknesses, which ultimately limits the optical absorption of a BP photodetector. This work demonstrates an absorption-boosting resonant metal-insulator-metal (MIM) metasurface grating integrated with a thin-film BP photodetector. We designed and fabricated different MIM gratings and characterized their spectral properties. Then, we show that an MIM structure increased room temperature responsivity from 12 to 77 mA W^-1 at 3.37 μm when integrated with a thin-film BP photodetector. Our results show that MIM structures simultaneously increase mid-wave infrared absorption and responsivity in a thin-film BP photodetector.

Ultra-Narrow Phosphorene Nanoribbons Produced by Facile Electrochemical Process

Phosphorene nanoribbons (PNRs) have inspired strong research interests to explore their exciting properties that are associated with the unique two-dimensional (2D) structure of phosphorene as well as the additional quantum confinement of the nanoribbon morphology, providing new materials strategy for electronic and optoelectronic applications. Despite several important properties of PNRs, the production of these structures with narrow widths is still a great challenge. Here, a facile and straightforward approach to synthesize PNRs via an electrochemical process that utilize the anisotropic Na+ diffusion barrier in black phosphorus (BP) along the [001] zigzag direction against the [100] armchair direction, is reported. The produced PNRs display widths of good uniformity (10.3 ± 3.8 nm) observed by high-resolution transmission electron microscopy, and the suppressed B2g vibrational mode from Raman spectroscopy results. More interestingly, when used in field-effect transistors, synthesized bundles exhibit the n-type behavior, which is dramatically different from bulk BP flakes which are p-type. This work provides insights into a new synthesis approach of PNRs with confined widths, paving the way toward the development of phosphorene and other highly anisotropic nanoribbon materials for high-quality electronic applications.

Wide-spectrum polarization-sensitive and fast-response photodetector based on 2D group IV-VI semiconductor tin selenide

Tin selenide (SnSe) has attracted considerable interest recently on account of its low-symmetry lattice structure, great compatibility with key semiconductor technology, and remarkable electrical and optical performance. SnSe-based polarization-sensitive photodetectors show promising application prospects because of their fast response and excellent photoelectric performance. Here, an in-plane anisotropic SnSe nanosheet was synthesized and reported in detail by applying angle-resolved polarized Raman spectroscopy (ARPRS), polarization-resolved optical microscopy(PROM), angle-resolved optical absorption spectroscopy (AROAS), and other crystal structure characterization methods. Moreover, SnSe crystals exhibit superior polarization detection performance with a high anisotropic photocurrent ratio (2.31 at 1064 nm) due to the structure formed by the Van der Waals superposition of covalently bonded atomic layers. Furthermore, SnSe-based photodetectors have high responsivity (9.27 A/W), high detectivity (4.08 × 1010 Jones), and fast response (in the order of nanoseconds). These results suggest a new method for fabricating 2D fast-response polarization-sensitive photodetectors in the future.

Enhancing the anti-oxidation stability of vapor-crystallized arsenic crystals via introducing iodine

The oxidation of arsenic restricts its application in high-performance electronic devices and functional materials. Herein, a removable iodine-regulation method was proposed for the first time to enhance the anti-oxidation behavior of arsenic. In a gradient of 500-650 ℃, the introduction of 0.6-5.0 at% iodine into arsenic vapor could regulate an arsenic crystal. The oxygen content on the regulated arsenic crystal surface was lowered below 2.5 at% after exposure to ambient conditions for 96 h, reducing over 90% compared with the control group. The residual iodine barrier, which was mainly in the As-I₂ state, suppressed the long-term oxidation of arsenic. First-principles calculation suggested that the adsorbed I₂ weakened the delocalization of lone-pair electrons and inhibited charge transfer from the arsenic surface. Iodine regulation stabilized arsenic surface, which preferred (003) or (012) facets. Their surface energies were 22.4 meV and 47.6 meV, respectively. The synergistic effect of surface stabilization and I₂ passivation lowered the surface energy and continuously slowed the oxidation of arsenic. Therefore, iodine regulation comprehensively enhanced the anti-oxidation properties of arsenic. Moreover, heating at 200 ℃ left the arsenic surface iodine content below 0.1 at% with little variation in structure. The improved anti-oxidation property of arsenic preserves resources for further advanced applications.

Black Phosphorus/Carbon Nanoframes for Efficient Flexible All-Solid-State Supercapacitor

A flexible all-solid-state supercapacitor with fast charging speed and high power density is a promising high-performance energy storage and sensor device in photovoltaic systems. Two-dimensional black phosphorus (BP) is a prospective electrode nanomaterial, but it struggles to fully exert its properties limited by its self-stacking. Herein, by embedding carbon nanoparticles into the interlayer of BP microplates, the designed BP/carbon nanoframe (BP/C NF) forms a certain nano-gap on the substrate for promoting the orderly transport of charges. The corresponding supercapacitor BP/C SC has a capacity of 372 F g^-1, which is higher than that constructed from BP microplates (32.6 F g^-1). Moreover, the BP/C SC exhibits good stability with a ca. 90% of capacitance retentions after 10,000 repeated bending and long-term cycles. Thus, the proposed strategy of using BP/carbon nanoframes is feasible to develop exceptional flexible energy devices, and it can guide the design of relevant two-dimensional nanocomposites.

Synergistic Lubrication Effect between Oxidized Black Phosphorus and Oil Molecules Triggers Superlubricity

Oxidized black phosphorus (BP) has been demonstrated as a promising oil-based nanoadditive because of its superior friction-reducing capability. However, the synergistic lubrication effect between oxidized BP and oil at the molecular level dominating the friction properties remains unclear. In this Letter, the synergistic lubrication effect between oxidized BP and two typical oil molecules (nonane and nonanoic acid) was explored with an atomic force microscope. The superlubricity of oxidized BP with an ultralow friction coefficient of 0.006 was achieved in the nonanoic acid environment, exhibiting a 96% reduction compared with that in the nonane environment. There was a confined nonanoic acid layer in the contact zone with a tilt angle of 35° because of the hydrogen bonding interaction, contributing to the superlubricity. This observation sheds light on the exploration of the lubrication mechanism of oxidized BP as a nanoadditive in oil, which reveals the considerable implications for the design of high-performance lubrication system.

Ultrasensitive, label-free voltammetric determination of norfloxacin based on molecularly imprinted polymers and Au nanoparticle-functionalized black phosphorus nanosheet nanocomposite

Norfloxacin (NOR) is an antibiotic commonly used to treat humans and food-producing animals. Owing to NOR abuse, its residues are frequently found in animal-derived food products and the surrounding environment. Therefore, development of an efficient analytical technique for the selective determination of trace NOR is greatly significant for food safety and environmental protection. Here, we fabricated an ultrasensitive, label-free molecularly imprinted polymer (MIP) voltammetric sensor for the selective determination of NOR, based on an Au nanoparticle-functionalized black phosphorus nanosheet nanocomposite (BPNS-AuNP) covered by a polypyrrole-imprinted film. BPNS-AuNP nanocomposites were prepared via an in-situ one-step method without the use of reducing agents. The imprinted polypyrrole film was formed on the surface of the BPNS-AuNPs in the presence of NOR. The physical properties and electrochemical behavior of the MIP/BPNS-AuNPs were investigated using various characterization techniques, and the analytical parameters were optimized. We found that BPNS-AuNPs improve the ambient stability and electrocatalytic activity, providing a large surface area for locating a higher number of specific recognition sites. Consequently, the MIP/BPNS-AuNP/GCE showed excellent sensing performance toward NOR, with a wide linear response range (0.1 nM - 10 μM), an extremely low limit of detection (0.012 nM), and extraordinary selectivity. Moreover, the MIP/BPNS-AuNP/GCE was used to determine NOR in various experimental samples with satisfactory results.

Anisotropic third-harmonic generation of exfoliated As2S3 thin flakes

Van der Waals (vdW) materials have recently attracted significant interest in the context of orientation-dependent linear and nonlinear optical properties. Recently, arsenic trisulfide (As₂S₃) or orpiment is identified as a new vdW layered material having anisotropic vibrational and optomechanical responses due to the reduced in-plane crystal symmetry, but its nonlinear optical response is still not well understood yet. Herein, the anisotropic third-harmonic generation (THG) response of mechanically exfoliated As₂S₃ thin flakes is reported. The polarization-dependent evolution of THG emission from butterfly-shaped pattern to four-lobe pattern is comprehensively explored. Moreover, the third-order nonlinear susceptibility of As₂S₃ crystal is extracted by analyzing the thickness-dependent THG emission. We anticipate that the discussed results will not only update the existing understanding on the nonlinear light-matter interaction in anisotropic vdW materials, but also promote future applications in integrated photonic circuits, on-chip nonlinear signal processing, and polarization-sensitive optical devices.

Plasmon-enhanced Raman spectroscopy of two-dimensional semiconductors

Two-dimensional (2D) semiconductors have grown fast into an extraordinary research field due to their unique physical properties compared to other semiconducting materials. The class of materials proved extremely fertile for both fundamental studies and a wide range of applications from electronics/spintronics/optoelectronics to photocatalysis and CO₂reduction. 2D materials are highly confined in the out-of-plane direction and often possess very good environmental stability. Therefore, they have also become a popular material system for the manipulation of optoelectronic properties via numerous external parameters. Being a versatile characterization technique, Raman spectroscopy is used extensively to study and characterize various physical properties of 2D materials. However, weak signals and low spatial resolution hinder its application in more advanced systems where decoding local information plays an important role in advancing our understanding of these materials for nanotechnology applications. In this regard, plasmon-enhanced Raman spectroscopy has been introduced in recent time to investigate local heterogeneous information of 2D semiconductors. In this review, we summarize the recent progress of plasmon-enhanced Raman spectroscopy of 2D semiconductors. We discuss the current state-of-art and provide future perspectives on this specific branch of Raman spectroscopy applied to 2D semiconductors.

On-chip integration of 2D Van der Waals germanium phosphide (GeP) for active silicon photonics devices

The outstanding performance and facile processability turn two-dimensional materials (2DMs) into the most sought-after class of semiconductors for optoelectronics applications. Yet, significant progress has been made toward the hybrid integration of these materials on silicon photonics (SiPh) platforms for a wide range of mid-infrared (MIR) applications. However, realizing 2D materials with a strong optical response in the NIR-MIR and excellent air stability is still a long-term goal. Here, we report a waveguide integrated photodetector based on a novel 2D GeP. This material uniquely combines narrow and wide tunable bandgap energies (0.51-1.68 eV), offering a broadband operation from visible to MIR spectral range. In a significant advantage over graphene devices, hybrid Si/GeP waveguide photodetectors work under bias with a low dark current of few nano-amps and demonstrate excellent stability and reproducibility. Additionally, 65 nm thick GeP devices integrated on silicon waveguides exhibit a remarkable photoresponsivity of 0.54 A/W and attain high external quantum efficiency of ∼ 51.3% under 1310 nm light and at room temperature. Furthermore, a measured absorption coefficient of 1.54 ± 0.3 dB/µm at 1310 nm suggests the potential of 2D GeP as an alternative infrared material with broad optical tunability and dynamic stability suitable for advanced optoelectronic integration.

Temperature-Dependent CAT-Like RGD-BPNS@SMFN Nanoplatform for PTT-PDT Self-Synergetic Tumor Phototherapy

Phototherapies such as photothermal therapy (PTT) and photodynamic therapy (PDT) are considered as alternatives for tumor remedies, because of their advantages of precise spatial orientation, minimally invasive, and nonradiative operation. However, most of phototherapeutic agents still suffer from low photothermal conversion efficacy and photodynamic performance, poor biocompatibility, and intratumor accumulation. Herein a biocompatible and target-deliverable PTT-PDT self-synergetic nanoplatform of RGD-BPNS@SMFN based on temperature-dependent catalase (CAT)-like behavior for tumor elimination is presented. The homogeneously dispersible nanoplatform is designed and fabricated through anchoring spherical manganese ferrite nanoparticles (SMFN) to black phosphorus nanosheets (BPNS), followed by arginine-glycine-aspartic acid (RGD) peptide modification. The nanoplatform exhibits excellent targeting ability and enhanced photonic response in comparison to plain BPNS and SMFN in vitro and in vivo. It is found that PTT and PDT have a self-synergetic behavior by means of the dual phototherapy mode interaction. The self-synergetic mechanism is mainly ascribed to PTT-promoted inherent CAT-like activity in the nanoplatform, which remodels the tumor hypoxia microenvironment and further ameliorates the PDT efficiency, providing promising high performance nanoplatform for synergetic dual mode phototherapy, enriching the design for the antitumor nanozyme.

Stability and passivation of 2D group VA elemental materials: black phosphorus and beyond

Since the successful isolation of graphene in 2004, two-dimensional (2D) materials have become one of the focuses in material science owing to their extraordinary physical and chemical properties. In particular, 2D group VA elemental materials exhibit fascinating thickness-dependent band structures. Unfortunately, the well-known instability issue hinders their fundamental researches and practical applications. In this review, we first discuss the degradation mechanism of black phosphorus (BP), a most studied group VA material. Next, we summarize the methods to enhance BP stability with the focus of multifunctional passivation. Finally, we briefly discuss the protection strategies of other emerging group VA materials in recent years. This review provides insight for the degradation mechanism and protecting strategy for 2D group VA elements materials, which will promote their potential applications in electronics, optoelectronics, and biomedicine.