Enhanced photocatalytic performance of Ag/TiO2 nanohybrid sensitized by black phosphorus nanosheets in visible and near-infrared light

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.

Recent Progress on Synthesis and Properties of Black Phosphorus and Phosphorene As New-Age Nanomaterials for Water Decontamination

Concerted efforts have been made in recent years to find solutions to water and wastewater treatment challenges and eliminate the difficulties associated with treatment methods. Various techniques are used to ensure the recycling and reuse of water resources. Owing to their excellent chemical, physical, and biological properties, nanomaterials play an important role when integrated into water/wastewater treatment technologies. Black phosphorus (BP) is a potential nanomaterial candidate for water and wastewater treatment, especially its monolayer 2D derivative called phosphorene. Phosphorene offers relative adjustability in its direct bandgap, high charge carrier mobility, and improved in-plane anisotropy compared to the most extensively studied 2D nanomaterials. In this study, we examined the physical and chemical characteristics and synthetic processes of BP and phosphorene. We provide an overview of the latest advancements in the main applications of BP and phosphorene in water/wastewater treatment, which are categorized as photocatalytic, adsorption, and membrane filtration processes. Additionally, we explore the existing difficulties in the integration of BP and phosphorene into water/wastewater treatment technologies and prospects for future research in this field. In summary, this review highlights the ongoing necessity for significant research efforts on the integration of BP and phosphorene in water and wastewater applications.

Advances in the Application of Black Phosphorus-Based Composite Biomedical Materials in the Field of Tissue Engineering

Black Phosphorus (BP) is a new semiconductor material with excellent biocompatibility, degradability, and optical and electrophysical properties. A growing number of studies show that BP has high potential applications in the biomedical field. This article aims to systematically review the research progress of BP composite medical materials in the field of tissue engineering, mining BP in bone regeneration, skin repair, nerve repair, inflammation, treatment methods, and the application mechanism. Furthermore, the paper discusses the shortcomings and future recommendations related to the development of BP. These shortcomings include stability, photothermal conversion capacity, preparation process, and other related issues. However, despite these challenges, the utilization of BP-based medical materials holds immense promise in revolutionizing the field of tissue repair.

Black Phosphorus-based Photocatalysts: Synthesis, Properties, and Applications

Photocatalysis is considered as an eco-friendly and sustainable strategy, since it uses abundant light for the advancement of the reaction, which is freely accessible and is devoid of environmental pollution. During the last decades, (nano)photocatalysts have gained broad industrial applications in terms of purification and detoxification of water as well as production of green fuels and hydrogen gas due to their special attributes. The degradation or remediation of toxic and hazardous compounds from the environment or changing them into non-toxic entities is a significant endeavor and necessary for the safety of humans, animals, and the environment. Black phosphorus (BP), a two-dimensional single-element material, has a marvelous structure, tunable bandgap, changeable morphology from bulk to nanosheet/quantum dot, and unique physicochemical properties, which makes it attractive material for photocatalytic applications, especially for sustainable development purposes. Since it can serve as a photocatalyst with or without coupling with other semiconductors, various aspects for multidimensional exploitation of BP are deliberated including their preparation via solvothermal, ball milling, calcination, and sonication methods to obtain BP from red phosphorus. The techniques for improving the photocatalytic and stability of BP-based composites are discussed along with their multifaceted applications for environmental remediation, pollution degradation, water splitting, N2 fixation, CO2 reduction, bacterial disinfection, H2 generation, and photodynamic therapy. Herein, most recent advancements pertaining to the photocatalytic applications of BP-based photocatalyst are cogitated, with a focus on their synthesis and properties as well as crucial challenges and future perspectives.

Catalysis-Mediated Male Contraception through Black Phosphorus Nanosheets

Nanocontraception has been proposed and received extensive attention in recent years for population control. However, currently developed methods for nanocontraception still face problems in efficacy and safety. Here, we propose catalysis-mediated oxidation as a new strategy for nanocontraception. With the catalytic production of highly oxidative species, male contraception was successfully achieved after the administration of black phosphorus nanosheets into the testes of male mice. Further mechanistic studies revealed that contraception was induced by oxidative stress and apoptosis of spermatogenesis cells. Meanwhile, the apoptosis of germ cells released testis antigen and induced immune cell infiltration, which enhanced reproductive damage. Notably, the introduced black phosphorus nanosheets naturally degraded during the catalytic oxidation process and ultimately converted to harmless phosphates, indicating the safety of the strategy. Furthermore, the catalysis-mediated strategy avoids utilizing additional inducers, such as near-infrared irradiation, magnetic fields, or ultrasound, which may cause severe pain. In summary, the proposed catalysis-mediated contraception can be a self-cleared, convenient, and safe strategy for controlling male fertility.

TiO2/BP/g-C3N4 heterojunction photocatalyst for the enhanced photocatalytic degradation of RhB

The efficiency of graphite carbon nitride (g-C3N4, CN) as a photocatalyst is limited due to its quick recombination of photogenerated carriers and layer re-stacking. To enhance its photocatalytic activity, a multi-heterojunction photocatalyst was developed using TiO2 and black phosphorus (BP) coupled with CN through a liquid-phase ultrasonic method. The composite, TiO2/BP/CN, demonstrated a wider range of light response and higher photo-induced carrier separation efficiency. The presence of TiO2 nanoparticles on CN nanolayers reduced interlayer stacking and increased specific surface area, thereby providing more reactive sites. As a result, the optimized TiO2/BP/CN composite demonstrated enhanced photocatalytic efficiency for the degradation of Rhodamine B (RhB), with a first-order kinetic constant of 2.8, 4.3, and 6.4 times that of CN, TiO2, and BP, respectively. Active substance capture experiments confirmed that superoxide radical (·O2) was the primary reactive species. This study highlights the potential of the developed TiO2/BP/CN composite as a promising photocatalyst for environmental remediation applications.

Seed Priming Modulates Physiological and Agronomic Attributes of Maize (Zea mays L.) under Induced Polyethylene Glycol Osmotic Stress

Drought and osmotic stresses are major threats to agricultural crops as they affect plants during their life cycle. The seeds are more susceptible to these stresses during germination and establishment of seedlings. To cope with these abiotic stresses, various seed priming techniques have broadly been used. The present study aimed to assess seed priming techniques under osmotic stress. Osmo-priming with chitosan (1 and 2%), hydro-priming with distilled water, and thermo-priming at 4 °C were used on the physiology and agronomy of Zea mays L. under polyethylene glycol (PEG-4000)-induced osmotic stress (-0.2 and -0.4 MPa). The vegetative response, osmolyte content, and antioxidant enzymes of two varieties (Pearl and Sargodha 2002 White) were studied under induced osmotic stress. The results showed that seed germination and seedling growth were inhibited under osmotic stress and germination percentage, and the seed vigor index was enhanced in both varieties of Z. mays L. with chitosan osmo-priming. Osmo-priming with chitosan and hydro-priming with distilled water modulated the level of photosynthetic pigments and proline, which were reduced under induced osmotic stress; moreover, the activities of antioxidant enzymes were improved significantly. In conclusion, osmotic stress adversely affects the growth and physiological attributes; on the contrary, seed priming ameliorated the stress tolerance resistance of Z. mays L. cultivars to PEG-induced osmotic stress by activating the natural antioxidation enzymatic system and accumulating osmolytes.

Modulation of the Structure of the Conjugated Polymer TMP and the Effect of Its Structure on the Catalytic Performance of TMP-TiO2 under Visible Light: Catalyst Preparation, Performance and Mechanism

The photocatalytic activity of titanium dioxide (TiO₂) is largely hindered by its low photoresponse and quantum efficiency. TiO₂ modified by conjugated polymers (CPs) is considered a promising approach to enhance the visible light responsiveness of TiO₂. In this work, in order to investigate the effect of CP structural changes on the photocatalytic performance of TiO₂ under visible light, trimesoyl chloride-melamine polymers (TMPs) with different structural characteristics were created by varying the parameters of the polymerisation process of tricarbonyl chloride (TMC) and melamine (M). The TMPs were subsequently composited with TiO₂ to form complex materials (TMP-TiO₂) using an in situ hydrothermal technique. The photocatalytic activity of TMP-TiO₂ was evaluated by the degradation of rhodamine B (RhB). The results showed that the trend of the structure of the TMP with the reaction conditions was consistent with the visible light responsiveness of TMP-TiO₂, and TMP (1:1)-TiO₂ had the best photocatalytic activity and could degrade 96.1% of the RhB. In conclusion, our study provided new insights into the influence of the structural changes of TMPs on the photocatalytic activity of TMP-TiO₂ under visible light, and it improves our understanding of how conjugated polymers affect the photocatalytic activity of TiO₂ under visible light.

2D phosphorene nanosheets, quantum dots, nanoribbons: synthesis and biomedical applications

Phosphorene, also known as black phosphorus (BP), is a two-dimensional (2D) material that has gained significant attention in several areas of current research. Its unique properties such as outstanding surface activity, an adjustable bandgap width, favorable on/off current ratios, infrared-light responsiveness, good biocompatibility, and fast biodegradation differentiate this material from other two-dimensional materials. The application of BP in the biomedical field has been rapidly emerging over the past few years. This article aimed to provide a comprehensive review of the recent progress on the unique properties and extensive medical applications for BP in bone, nerve, skin, kidney, cancer, and biosensing related treatment. The details of applications of BP in these fields were summarized and discussed.

One-step hydrothermal synthesis of a ternary heterojunction g-C3N4/Bi2S3/In2S3 photocatalyst and its enhanced photocatalytic performance

In recent years, photoelectrocatalysis has been one of the hotspots of research. Graphite-like carbon nitride (g-C3N4) is one of the few non-metal semiconductors known and has good potential in the field of photocatalysis due to its simple preparation method and visible light effects. In this study, a method for compounding two semiconductor materials, In2S3 and Bi2S3, on the surface of g-C3N4 via a one-step hydrothermal method is reported, and it was found that this resulting material showed remarkable properties. The advantages of this method are as follows: (1) the formation of a heterojunction, which accelerates the separation efficiency of photogenerated carriers; (2) a large number of holes and defects on the surface of g-C3N4 are conducive to the nucleation, crystallisation and growth of In2S3 and Bi2S3. Compared with its counterpart catalysts, the CN/In2S3/Bi2S3 composite catalyst has significantly improved performance. Due to its high degree of crystallinity, the adsorption capacity of the catalyst itself is also significantly improved. In addition, the stability of the composite material maintains 90.9% after four cycles of use, and the structure is not damaged. In summary, CN/Bi2S3/In2S3 composite materials are believed to have broad application potential in the treatment of dye wastewater.

Engineered two-dimensional nanomaterials: an emerging paradigm for water purification and monitoring

Water scarcity has become an increasingly complex challenge with the growth of the global population, economic expansion, and climate change, highlighting the demand for advanced water treatment technologies that can provide clean water in a scalable, reliable, affordable, and sustainable manner. Recent advancements on 2D nanomaterials (2DM) open a new pathway for addressing the grand challenge of water treatment owing to their unique structures and superior properties. Emerging 2D nanostructures such as graphene, MoS₂, MXene, h-BN, g-C₃N₄, and black phosphorus have demonstrated an unprecedented surface-to-volume ratio, which promises ultralow material use, ultrafast processing time, and ultrahigh treatment efficiency for water cleaning/monitoring. In this review, we provide a state-of-the-art account on engineered 2D nanomaterials and their applications in emerging water technologies, involving separation, adsorption, photocatalysis, and pollutant detection. The fundamental design strategies of 2DM are discussed with emphasis on their physicochemical properties, underlying mechanism and targeted applications in different scenarios. This review concludes with a perspective on the pressing challenges and emerging opportunities in 2DM-enabled wastewater treatment and water-quality monitoring. This review can help to elaborate the structure-processing-property relationship of 2DM, and aims to guide the design of next-generation 2DM systems for the development of selective, multifunctional, programmable, and even intelligent water technologies. The global significance of clean water for future generations sheds new light and much inspiration in this rising field to enhance the efficiency and affordability of water treatment and secure a global water supply in a growing portion of the world.

Green synthesis of boron and nitrogen co-doped TiO2 with rich B-N motifs as Lewis acid-base couples for the effective artificial CO2 photoreduction under simulated sunlight

Boron and nitrogen co-doped Titanium dioxide (TiO₂) nanosheets (BNT) with high surface area of 136.5 m² g^-1 were synthesized using ammonia borane as the green and triple-functional regent, which avoids the harmful and explosive reducing regents commonly used to create surface defects on TiO₂. The decomposition of ammonia borane could incorporate reactive Lewis acid-base (B, N) pairs, together with the as-generated H₂ to create mesoporous structure and rich oxygen vacancies in pristine TiO₂. The BNTs prepared from various ammonia borane loading are evaluated in photoreduction of carbon dioxide (CO₂) with steam under simulated sunlight, achieving about 3.5 times higher carbon monoxide (CO) production than pristine TiO₂ under the same conditions. Steady state and transient optical measurements indicated BNT with reduced band gap, rich defect states and elevated conduction band position could enhance the light harvesting efficiency and promote the charge transfer at the catalyst/CO₂ interface. Density functional theory simulation and in situ FTIR suggest that the Lewis acid-base (B, N) pairs on BNT may very substantially increase the activation of inert CO₂ which facilitates their photoreduction with the hydrogen from the water splitting at the surface defects on TiO₂. Finally, a reaction mechanism of Lewis acid-base assisted CO₂ photoreduction leading to substantially improved performance is proposed.

Nanocopper-loaded Black phosphorus nanocomposites for efficient synergistic antibacterial application

Novel nanocopper-loaded black phosphorus (BP/Cu) nanocomposites were synthesized to synergistically exert enhanced antibacterial activities aimed at reducing antibiotics abuse. First, both BP and Cu display low biotoxicity, broadening their application in the microbiological field. Second, the unique electronic properties of BP enable BP/Cu nanocomposites to amplify antibacterial effects via interfacial charge transfer, resulting in a surge of reactive oxygen species (ROS). Third, BP/Cu nanocomposites are relatively stable, which helps to avoid the problem that nanocopper alone is highly oxidized. Finally, BP/Cu was synthesized in an environmentally-friendly manner by a one-step reduction method. The BP/Cu nanocomposites were characterized by transmission electron microscopy and atomic force microscopy. Their antibacterial properties were investigated comprehensively and discussed in detail by inhibition zone assays, dynamic growth curves, membrane potential assays, and live/dead baclight bacterial viability assays, all of which revealed the antimicrobial activities of BP/Cu nanocomposites. Absorption spectra were measured to determine which ROS species were responsible for the bactericidal mechanisms. In summary, our results demonstrated the potential of nanocomposites based on BP in antibacterial therapy due to its excellent electronic properties and outstanding biological performance. This will pave the way for avoiding antibiotic overuse and for providing security to humans and the environment.

Black phosphorus for fighting antibiotic-resistant bacteria: What is known and what is missing

Recently, two-dimensional black phosphorus (BP) nanomaterial has captured much attention due to its superb physiochemical and electronic properties and various promising biomedical applications. However, relatively few studies have explored its antimicrobial properties, particularly for targeting antibiotic-resistant pathogens. A comprehensive understanding of the bactericidal mechanisms of BP is essential for application of this material as an antimicrobial. This review discusses the physicochemical and electronic properties of BP that are relevant for antimicrobial applications, especially the unique characteristics that may play a role in overcoming drug resistance. The literature is discussed in the context of what is known and what information is missing. We also highlight the differences and advantages of BP over other two-dimensional nanomaterials (i.e., graphene oxide and molybdenum disulfide) for bactericidal activity. Finally, we analyze existing challenges and note topics that require future investigation to overcome current inadequacies, aiming to assist the safe development of BP-based nanotechnology for pathogen control.

Intercalation of Nb2O5 nano-flowers into the walls of few-layer black phosphorus creating a heterostructure of FL-BP@Nb2O5 with the potential for environmental application

Herein we report the successful exfoliation of few-layer BP (FL-BP) from bulk BP via ultrasonication in N-methylpyrrolidone (NMP). FL-BP exhibited an orthorhombic phase structure similar to that of bulk BP with weak electrostatic out-of-plane interactions and strong ionic in-plane bonds. The weakened out-of-plane bonds allowed the intercalation of Nb2O5 nano-flowers that were hydrothermally synthesized, forming an intimate contact with the exfoliated BP. The successful formation of the heterointerface was confirmed by the co-existence of crystal phases of both compounds as per the XRD results. The formation of the new intrinsic Nb-P bond was confirmed by the presence of Raman shoulders of both compounds, further substantiated by the XPS analysis. The heterointerface enhanced Nb2O5 light-harvesting capacity as per the UV-vis measurements. The FL-BP's properties of higher carrier effective mass and density were successfully incorporated in the composite, implying an increased flow of electrons in the composite's lattice structure. This was displayed by the great suppression of the fast recombination rate of charge carriers in the composites. The 3% BP@Nb2O5 composite exhibited excellent optoelectrical properties, compared to the other composites, as suggested by the microstrain calculations, PL, and the EIS data. Mott-Schottky plots verified the p-n type heterojunction formed in the composites, and further verified the increased electron density/concentration in the composites, with respect to Nb2O5. Noteworthy, the incorporation of FL-BP in the lattice of Nb2O5 increased the surface area and the pore size and volume, which is a character beneficial for photocatalysis as it presents active sites and diffusion pathways.

Effect of Ag loading position on the photocatalytic performance of TiO2 nanocolumn arrays

Plasmonic metal/semiconductor composites have attracted great attention for efficient solar energy harvesting in photovoltaic and photocatalytic applications owing to their extremely high visible-light absorption and tuned effective band gap. In this work, Ag-loaded TiO₂ nanocolumn (Ag-TNC) arrays were fabricated based on anodic aluminum oxide (AAO) template by combining atomic layer deposition (ALD) and vacuum evaporation. The effects of the Ag loading position and deposition thickness, and the morphology, structure and composition of Ag-deposited TNC arrays on its optical and photocatalytic properties were studied. The Ag-filled TiO₂ (AFT) nanocolumn arrays exhibited higher removal efficiency of methylene blue (MB) compared with Ag-coated TiO₂ (ACT) nanocolumn arrays and pure TiO₂ nanocolumns arrays. Both experimental and theoretical simulation results demonstrated that the enhanced photocatalytic performance of AFT nanocolumn arrays was attributed to the surface plasmon resonance (SPR) of Ag and the absorption of light by TiO₂. These results represent a promising step forward to the development of high-performance photocatalysts for energy conversion and storage.

Ni-doped and Ni/Cr co-doped TiO2 nanotubes for enhancement of photocatalytic degradation of methylene blue

Ni-doped and Ni/Cr co-doped TiO₂ nanotubes were successfully synthesized using a novel hydrothermal method. The surface and bulk properties of as-synthesized nanopowders were characterized using various microstructural and optical techniques. The photocatalytic ability of these nanopowders was investigated systematically for the decomposition of methylene blue dye (MB) under visible light illumination. The morphological results revealed the structural transformation of TiO₂ nanotubes to nanosheets, and further to a mixture of nanosheet/nanotube on doping with Ni and co-doping of Ni/Cr, respectively. Moreover, the Ni doping causes an optical absorption edge shifts towards lower wavelengths, while doping by Ni/Cr results to an optical absorption edge shifts towards higher wavelength in comparison to TiO₂-nanotubes. Also, Ni-doping and Ni/Cr co-doping strongly affects the Raman vibrational modes owing to the changes in interplanar distance, crystallite size, dislocation density, and crystal microstrains. Among the undoped, doped and co-doped TiO₂ nanoparticles, the 6Ni/4Cr co-doped TiO₂ exhibited a higher efficiency of 95.6% and excellent stability towards the photocatalytic degradation of MB. It is attributed to the availability of many carriers for the efficient photo-oxidation within the UV-Vis optical absorption range. Also, the photocatalytic reaction kinetics and degradation mechanism of MB were discussed.

Enhanced photocatalytic properties of TiO2 nanosheets@2D layered black phosphorus composite with high stability under hydro-oxygen environment

Black phosphorus (BP) has gained great attention as a potential candidate in the photocatalytic field due to its tunable bandgap and high-mobility features, however, poor stability behavior and the high charge recombination of BP limit its practical application. In the present work, a liquid phase exfoliation method is employed to prepare layered BP. The as-prepared layered BP is decorated on TiO2 nanosheets to form a TiO2 nanosheets@BP composite, which stabilizes BP existence under a hydro-oxygen environment. Whereafter, the photocatalytic properties of the TiO2 nanosheets@BP composite towards the degradation of Rhodamine B (RhB) are proven to be greatly enhanced compared to those of pure layered BP and TiO2 nanosheets, and the photodegradation rate reached 98% after 120 minutes irradiation under UV-Vis light. It is worth mentioning that the photocatalytic cycling performance of the TiO2 nanosheets@BP composite remained at 92.5% under the irradiation of UV-Vis light after three cycles. The main reason for this lies in the fact that the formation of the TiO2 nanosheets@BP composite may favor light absorption and effectively reduce the recombination of electron-hole pairs.

Rational design of a polypyrrole-based competent bifunctional magnetic nanocatalyst

The combination of conducting polymers with semiconductors for the fabrication of organic/inorganic hybrid nanocatalysts is one of the most promising research areas for many applications. In this work, the synthesized nanocomposite combines several advantages such as the photoresponse shift from the UV region toward visible light by narrowing the band gap of the semiconductor, magnetic separation ability and dual applications including the catalytic reduction of p-nitrophenol (PNP) and the photocatalytic degradation of methylene blue (MB) dye. In addition to the core magnetite nanoparticles (NPs), the synthesized nanocomposite contains polypyrrole (PPY) and TiO₂ shells that are decorated with silver metal NPs to prevent electron–hole recombination and to enhance the catalytic performance. Indeed, the catalytic PNP reduction experiments reveal that the synthesized nanocomposite exhibits significantly high catalytic activity with a rate constant of 0.1169 min⁻¹. Moreover, the photocatalytic experiments show that the synthesized nanophotocatalyst has a boosting effect toward MB dye degradation under normal daytime visible light irradiation with a rate constant of 6.38 × 10⁻² min⁻¹. The synergetic effect between silver NPs, PPY and TiO₂ is thought to play a fundamental role in enhancing the photocatalytic activity.

An efficient method to synthesize a magnetic nanocomposite with dual catalytic activities with a synergetic effect between Ag nanoparticles, polypyrrole and TiO₂ is described.