Allotrope Of Phosphorus Research Articles

Highly anisotropic and tunable charge carrier of monolayer phosphorus allotropes by bi-axial strain

The complex variation of electronic properties and carrier mobility of four typical allotropes of phosphorus are investigated using first-principles calculations of bi-axial strain. Our study shows that the electronic properties and carrier mobility of single-layer α-, β-, γ- and δ-P are sensitive to bi-axial strain, and that the carrier mobility can even be increased by several orders of magnitude under specific tensile or compressive strain. Moreover, the anisotropy of their mobility in the two-dimensional plane shows different changes according to the variation of the bi-axial strain. In particular, the electron mobility of α-P (γ-P) along the two main axis directions is reversed when the bi-axial strain increased by 5% (−4%). This transformation is mainly caused by changes in the effective mass anisotropy due to alterations in band dispersion under external strain, as illustrated by the distribution of effective mass anisotropy and the corresponding changes of electronic properties under strain.

Graphene gets bent

Graphene gets bent

High Yield Synthesis of Violet Phosphorus Crystals

Violet phosphorus is the most stable phosphorus allotrope with a layered structure. The corresponding violet phosphorene, a more stable two-dimensional semiconducting structure than black phosphorene, is a promising two-dimensional material for electronic and optoelectronic devices. The synthesis of violet phosphorus is the key factor to its experimental research. However, no clear evidence has been reported for the synthesis of violet phosphorus since its first proposal in 1865. The violet phosphorus was even debated to be a metastable intermediate phase. Until recently, the violet phosphorus crystals have just been successfully produced and exfoliated to give violet phosphorene. High yield synthesis of highly crystalline and pure violet phosphorus is crucial for the further exploration of violet phosphorus and phosphorene. In this work, highly crystalline and pure violet phosphorus crystals have been produced with a yield as high as 80%. The vapor transport, nucleation, crystal growth conditions, and synthesis mechanism have been studied to obtain violet phosphorus instead of black phosphorus. The mixture of transport agents and amorphous red phosphorus was heated to 600 °C to form P–Sn–I vapor and transported to the cooler zone (580 °C). The phosphorus was separated out from the P–Sn–I composites after cooling down to 530 °C to form violet phosphorus nuclei. The nucleation time and further cooling time correspond to the amount and crystallinity of violet phosphorus crystals. The precipitation has been demonstrated to be SnI2 crystals with a space group of C2/m (12) after the growth of violet phosphorus crystals. The synthesis of highly crystalline and pure violet phosphorus with high yield provides the application possibility of violet phosphorus and phosphorene in mechanic, electronic, optoelectronic, catalysts, and medical fields.

Crystalline Red Phosphorus Nanoribbons: Large-Scale Synthesis and Electrochemical Nitrogen Fixation.

Two dimensional (2D) nanoribbons constitute an emerging nanoarchitecture for advanced microelectronics and energy conversion due to the stronger size confinement effects compared to traditional nanosheets. Triclinic crystalline red phosphorus (cRP) composed by a layered structure is a promising 2D phosphorus allotrope and the tube-like substructure is beneficial to the construction of nanoribbons. In this work, few-layer cRP nanoribbons are synthesized and the effectiveness in the electrochemical nitrogen reduction reaction (NRR) is investigated. An iodine-assisted chemical vapor transport (CVT) method is developed to synthesize circa 10 g of bulk cRP lumps with a yield of over 99 %. With the aid of probe ultrasonic treatment, high-quality cRP microcrystals are exfoliated into few-layer nanoribbons (cRP NRs) with large aspect ratios. As non-metallic materials, cRP NRs are suitable for the electrochemical nitrogen reduction reaction. The ammonia yield is 15.4 μg h-1 mgcat. -1 at -0.4 V vs. reversible hydrogen electrode in a neutral electrolyte under ambient conditions and the Faradaic efficiency is 9.4 % at -0.2 V. Not only is cRP a promising catalyst, but also the novel strategy expands the application of phosphorus-based 2D structures beyond that of traditional nanosheets.

Crystalline Red Phosphorus Nanoribbons: Large‐Scale Synthesis and Electrochemical Nitrogen Fixation

AbstractTwo dimensional (2D) nanoribbons constitute an emerging nanoarchitecture for advanced microelectronics and energy conversion due to the stronger size confinement effects compared to traditional nanosheets. Triclinic crystalline red phosphorus (cRP) composed by a layered structure is a promising 2D phosphorus allotrope and the tube‐like substructure is beneficial to the construction of nanoribbons. In this work, few‐layer cRP nanoribbons are synthesized and the effectiveness in the electrochemical nitrogen reduction reaction (NRR) is investigated. An iodine‐assisted chemical vapor transport (CVT) method is developed to synthesize circa 10 g of bulk cRP lumps with a yield of over 99 %. With the aid of probe ultrasonic treatment, high‐quality cRP microcrystals are exfoliated into few‐layer nanoribbons (cRP NRs) with large aspect ratios. As non‐metallic materials, cRP NRs are suitable for the electrochemical nitrogen reduction reaction. The ammonia yield is 15.4 μg h−1 mgcat.−1 at −0.4 V vs. reversible hydrogen electrode in a neutral electrolyte under ambient conditions and the Faradaic efficiency is 9.4 % at −0.2 V. Not only is cRP a promising catalyst, but also the novel strategy expands the application of phosphorus‐based 2D structures beyond that of traditional nanosheets.

Hierarchically Structured Allotropes of Phosphorus from Data‐Driven Exploration

AbstractThe discovery of materials is increasingly guided by quantum‐mechanical crystal‐structure prediction, but the structural complexity in bulk and nanoscale materials remains a bottleneck. Here we demonstrate how data‐driven approaches can vastly accelerate the search for complex structures, combining a machine‐learning (ML) model for the potential‐energy surface with efficient, fragment‐based searching. We use the characteristic building units observed in Hittorf's and fibrous phosphorus to seed stochastic (“random”) structure searches over hundreds of thousands of runs. Our study identifies a family of hierarchically structured allotropes based on a P8 cage as principal building unit, including one‐dimensional (1D) single and double helix structures, nanowires, and two‐dimensional (2D) phosphorene allotropes with square‐lattice and kagome topologies. These findings yield new insight into the intriguingly diverse structural chemistry of phosphorus, and they provide an example for how ML methods may, in the long run, be expected to accelerate the discovery of hierarchical nanostructures.

Hierarchically Structured Allotropes of Phosphorus from Data-Driven Exploration.

The discovery of materials is increasingly guided by quantum‐mechanical crystal‐structure prediction, but the structural complexity in bulk and nanoscale materials remains a bottleneck. Here we demonstrate how data‐driven approaches can vastly accelerate the search for complex structures, combining a machine‐learning (ML) model for the potential‐energy surface with efficient, fragment‐based searching. We use the characteristic building units observed in Hittorf's and fibrous phosphorus to seed stochastic (“random”) structure searches over hundreds of thousands of runs. Our study identifies a family of hierarchically structured allotropes based on a P8 cage as principal building unit, including one‐dimensional (1D) single and double helix structures, nanowires, and two‐dimensional (2D) phosphorene allotropes with square‐lattice and kagome topologies. These findings yield new insight into the intriguingly diverse structural chemistry of phosphorus, and they provide an example for how ML methods may, in the long run, be expected to accelerate the discovery of hierarchical nanostructures.

Integrated effect of NH2-functionalized/triazine based covalent organic framework black phosphorus on reducing fire hazards of epoxy nanocomposites

As the most thermodynamical and chemical stable allotrope of phosphorus, black phosphorus (BP) has recently generated huge research interest due to its high carrier mobility, semi-conductive property and an intrinsically tunable bandgap. BP has shown potential application in flame retardant polymer nanocomposites as emerging nanofiller. However the utilization of BP in polymer nanocompsoites still remains a huge challenge as it is prone to oxidation in water under air condition and pristine BP shows limited flame retardancy efficiency. In order to solve these issues, herein, triazine based organic framework was grown onto the surface of two-dimensional (2D) BP by in situ polymerization, resulting in the formation of organic-inorganic hybrids (BP-NH-TOF) which were subsequently incorporated into epoxy resin to fabricate the final nanocomposites. With increasing the loading of BP-NH-TOF in EP nanocomposites, the corresponding PHRR, THR, TSR and SPR values were reduced remarkably. For example, the addition of 2 wt% BP-NH-TOF results in a maximum decrease in PHRR (61.2%) and THR (44.3%) along with the dramatically improved LOI (29.0%) and UL-94 (V-0) performance, in addition to the obvious reduction of the amount of toxic carbon monoxide and flammable volatile products. Meanwhile, the mechanical properties of EP/BP-NH-TOF nanocomposites are enhanced significantly, e.g. 67.1% improvement in storage modulus at 1 wt% of BP-NH-TOF loading along with the improved glass transition temperature. The outstanding fire safety and mechanical properties of EP nanocomposites are attributed to the synergistic action of BP-NH-TOF hybrids. This work provides a facile method to prepared functionlized BP with the application in high performance flame retardant polymer nanocomposites.

(Invited) Rich Electron-Phonon Interactions in Atomically-Thin Black Phosphorus

Black phosphorus is the most stable allotrope of phosphorus and exhibits a layered structure that can be exfoliated down to a single monolayer. This elemental 2D semiconductor offers several distinctive features unmatched by none of the other 2D materials. For instance, it offers high carrier mobilities, strongly anisotropic optical, electrical and mechanical properties along all three principal crystal axes, a thickness-tunable gap spanning the near-IR and the short wavelength IR spectral region, a direct gap that efficiently interacts with light irrespective of sample thickness, and, most usually, a gap that can be dynamically tuned by an external electric field to an extent rarely seen from other semiconductor materials. For these reasons, black phosphorus opens many interesting prospects for the design of optoelectronic devices with novel functionalities.I will introduce this 2D material, discuss its most intriguing characteristics and then present results from an elaborate Raman study. In addition to bulk modes, atomically-thin black phosphorus exhibits unexpected bulk-forbidden Raman-allowed modes. The most obvious ones result from the lack of translational symmetry in few-layer samples, where the combination of infrared-allowed modes in adjacent layers combine to generate new Raman-allowed modes. Normally very weak, this phenomenon is prominent in the bilayer due to resonant effects in the electronic band structure. Polarization-resolved measurements on first order modes reveal powerful insights on the complex Raman tensor elements, their relative strengths, and their evolution as a function of sample thickness. For instance, anisotropy dominates the monolayer response and interlayer interactions in multilayers reduce all observed anisotropies.In addition to first-order Raman modes, four new second-order modes are identified in the close vicinity of the well-established symmetrical Ag modes. Their evolutions as a function of sample thickness, excitation wavelength, and defect density indicate that they are defect-activated and involve high-momentum phonons in a doubly resonant Raman process. Ab-initio calculations of the monolayer band structure and Raman intensity simulations reveal that phonon scattering predominantly involves intravalley contributions either in the zigzag or armchair cristal directions. Second order modes have played an important role in the development of carbon-based materials, including graphene, and their existence in black phosphorus offers new ways to probe carrier mobility, defect density, doping levels as well as chemical reactivity and mechanical stress.Instrumental in the scientific and technological development of 2D materials, Raman spectroscopy appears to be an even more powerful technique for the study of orthorhombic materials: the Raman-allowed modes express changes in permittivity as a function of atomic motion, couple in a unique way with the anisotropic electronic band structure through very restrictive selection rules. These connections will be illustrated by experimental results discussed using arguments relating to the symmetry of black phosphorus.

Fibrous Phosphorus Quantum Dots for Cell Imaging

Fibrous phosphorus is a crystalline structure belonging to the extensive family of phosphorus allotropes. The material’s structure consists of 1D tubular layers held together by van der Waals forces and is a semiconductor with an optical band gap of 2.1 eV in its bulk form. With these properties in mind, we developed a facile solution-based method for the fabrication of fibrous phosphorus quantum dots (FPQDs). The FPQDs were prepared by sonicating the material in N-methylpyrrolidone and centrifuging to separate by size. The average size of the quantum dots is 3.8 ± 0.9 nm with a height profile of 2.7 ± 1.3 nm. The as-prepared FPQDs show fluorescence properties with emission in the indigo-blue region and a band gap of 3.3 eV and show remarkable stability when exposed to air and light. As a proof-of-concept of its properties, we used FPQDs as a fluorescent label in the bioimaging of human adenocarcinoma cells.

Changing the Phosphorus Allotrope from a Square Columnar Structure to a Planar Zigzag Nanoribbon by Increasing the Diameter of Carbon Nanotube Nanoreactors.

Elemental phosphorus nanostructures are notorious for a large number of allotropes, which limits their usefulness as semiconductors. To limit this structural diversity, we synthesize selectively quasi-1D phosphorus nanostructures inside carbon nanotubes (CNTs) that act both as stable templates and nanoreactors. Whereas zigzag phosphorus nanoribbons form preferably in CNTs with an inner diameter exceeding 1.4 nm, a previously unknown square columnar structure of phosphorus is observed to form inside narrower nanotubes. Our findings are supported by electron microscopy and Raman spectroscopy observations as well as ab initio density functional theory calculations. Our computational results suggest that square columnar structures form preferably in CNTs with an inner diameter around 1.0 nm, whereas black phosphorus nanoribbons form preferably inside CNTs with a 4.1 nm inner diameter, with zigzag nanoribbons energetically favored over armchair nanoribbons. Our theoretical predictions agree with the experimental findings.

Theoretical anchoring effect of new phosphorus allotropes for lithium-sulfur batteries.

The lithium-sulfur battery system has appeared as a new-generation alternative to lithium-ion batteries with 5-7 times higher specific energy density than conventional lithium-ion batteries. But its commercial implementation is still impeded by a series of technical challenges. Modifying separation with the anchoring material is viewed as an effective way to overcome these problems and achieve long-term cycling stability and high-rate performance. In this paper, eight phosphorus allotropes, α-P, β-P, γ-P, δ-P, ε-P, ζ-P, θ-P and η-P, are investigated as anchoring materials for separation in lithium-sulfur batteries based on binding energy and diffusion barrier discussion. The results show that the crystal structures of phosphorus polymorphs are crucial to the suitability of their application as anchoring materials for lithium-sulfur batteries. The binding energy results show that except ε-P, all the other phosphorus allotropes can strike a balance between binding strength and intactness of the Li2Sn species. Among these, ε-P composed of P4 squares is a strong anchoring material and may lead to the decomposition of the Li2S cluster. Furthermore, for Li atoms and lithium sulfides, the most convenient diffusion paths are all along the grooves in the phosphorus monolayers, including the life-boat shaped (α-P, γ-P, δ-P and ε-P), wave shaped (β-P, ζ-P) and back-to-back shaped (θ-P, η-P) grooves. Except ε-P, all the other phosphorus allotropes can be applied to modify the separation for lithium-sulfur batteries. But among these, α-P, β-P, γ-P and δ-P composed of P6 hexagons can act as more suitable substrates for Li atom and lithium sulfide diffusion with lower barriers. As a result, α-P, β-P, γ-P and δ-P composed of P6 hexagons are good choices as separation modification materials in lithium-sulfur batteries among phosphorus allotropes. In addition, the structure correlations among α-P, β-P, γ-P and δ-P, and the likely conversion pathways from α-P to β-P, from β-P to γ-P, and from γ-P to δ-P are discussed.

Structure of Blue Phosphorus Grown on Au(111) Surface Revisited

Blue phosphorus (BlueP) is predicted as a new two-dimensional allotrope of black phosphorus with a great potential in electronic device applications. Recently, the growth of BlueP on Au(111) surfac...

Structure and Properties of Violet Phosphorus and Its Phosphorene Exfoliation

AbstractBlack phosphorene has attracted much attention as a semiconducting two‐dimensional material. Violet phosphorus is another layered semiconducting phosphorus allotrope with unique electronic and optoelectronic properties. However, no confirmed violet crystals or reliable lattice structure of violet phosphorus had been obtained. Now, violet phosphorus single crystals were produced and the lattice structure has been obtained by single‐crystal x‐ray diffraction to be monoclinic with space group of P2/n (13) (a=9.210, b=9.128, c=21.893 Å, β=97.776°). The lattice structure obtained was confirmed to be reliable and stable. The optical band gap of violet phosphorus is around 1.7 eV, which is slightly larger than the calculated value. The thermal decomposition temperature was 52 °C higher than its black phosphorus counterpart, which was assumed to be the most stable form. Violet phosphorene was easily obtained by both mechanical and solution exfoliation under ambient conditions.

Structure and Properties of Violet Phosphorus and Its Phosphorene Exfoliation.

Black phosphorene has attracted much attention as a semiconducting two-dimensional material. Violet phosphorus is another layered semiconducting phosphorus allotrope with unique electronic and optoelectronic properties. However, no confirmed violet crystals or reliable lattice structure of violet phosphorus had been obtained. Now, violet phosphorus single crystals were produced and the lattice structure has been obtained by single-crystal x-ray diffraction to be monoclinic with space group of P2/n (13) (a=9.210, b=9.128, c=21.893 Å, β=97.776°). The lattice structure obtained was confirmed to be reliable and stable. The optical band gap of violet phosphorus is around 1.7 eV, which is slightly larger than the calculated value. The thermal decomposition temperature was 52 °C higher than its black phosphorus counterpart, which was assumed to be the most stable form. Violet phosphorene was easily obtained by both mechanical and solution exfoliation under ambient conditions.

Reversible Alloying of Phosphorene with Potassium and Its Stabilization Using Reduced Graphene Oxide Buffer Layers.

High specific capacity materials that can store potassium (K) are essential for next-generation K-ion batteries. One such candidate material is phosphorene (the 2D allotrope of phosphorus (P)), but the potassiation capability of phosphorene has not yet been established. Here we systematically investigate the alloying of few-layer phosphorene (FLP) with K. Unlike lithium (Li) and sodium (Na), which form Li3P and Na3P, FLP alloys with K to form K4P3, which was confirmed by ex situ X-ray characterization as well as density functional theory calculations. The formation of K4P3 results in high specific capacity (∼1200 mAh g-1) but poor cyclic stability (only ∼9% capacity retention in subsequent cycles). We show that this capacity fade can be successfully mitigated by the use of reduced graphene oxide (rGO) as buffer layers to suppress the pulverization of FLP. We studied the performance of rGO and single-walled carbon nanotubes (sCNTs) as buffer materials and found that rGO being a 2D material can better encapsulate and protect FLP relative to 1D sCNTs. The half-cell performance of FLP/rGO could also be successfully reproduced in a full-cell configuration, indicating the possibility of high-performance K-ion batteries that could offer a sustainable and low-cost alternative to Li-ion technology.

The structure and electronic properties of crimson phosphorus

Semiconducting layered phosphorus allotropes, such as black and violet phosphorus, are attracting more and more attention due to their predicted high hole mobilities (up to 1000 cm2 V−2 s−1). Violet phosphorus is assumed to be the intermediate structure between amorphous red phosphorus and black phosphorus. Is there any other reasonable and stable allotrope between them? An unexplored layered phosphorus allotrope, crimson phosphorus, has been predicted by the ab initio method. The crystal structure, elastic moduli, band structure, and charge carrier mobility of crimson phosphorus have been investigated. A higher symmetry with similar energetic stability and a narrower bandgap compared to those of violet phosphorus has been obtained by crimson phosphorus. The hole mobilities of crimson phosphorus have been calculated to be 5383 (μx) and 1072 (μy) cm2 V−1 s−1, which are much higher than those of violet phosphorus (μx: 91 cm2 V−1 s−1 and μy: 27 cm2 V−1 s−1) and black phosphorus (μx: 3525 cm2 V−1 s−1 and μy: 9 cm2 V−1 s−1). Additionally, much higher hole mobility anisotropy has been demonstrated by crimson phosphorus. Lower electron mobility compared with those of black and violet ones has been obtained by crimson phosphorus. The unique electronic properties of crimson phosphorus provide promising 2D materials for desired devices.

Urchin-like fibrous red phosphorus as an efficient photocatalyst for solar-light-driven disinfection of E. coli

Fibrous red phosphorus (FRP), a crystalline allotrope of red phosphorus has interesting structural features and promising applications in the area of energy storage devices and photocatalysis. In this work, we employ a solid state method to synthesize crystalline red phosphorus which results in an interesting urchin-like structure. The microstructure shows a bundle of fibers originating from a core. Detailed characterization points to the presence of FRP as the major allotrope in the product. Photocatalytic activity of FRP is examined towards the solar disinfection of water using E. coli as a model pollutant. The bandgap of the synthesized FRP is 1.9 eV and it has optimum valence band and conduction band levels to generate reactive oxygen species (ROS) such as superoxide radical and H2O2. OH· is then produced from the H2O2. These photo-generated ROS are successful in bringing 8 log reduction in the concentration of E. coli in 30 min, which compares extremely well with values reported from other catalysts.

Phosphorene and Black Phosphorus: The 31P NMR View.

This work aims at characterizing for the first time the 31P spin interactions determining the nuclear magnetic resonance (NMR) properties of solid black phosphorus (bP) and of its few-layer exfoliated form (fl-bP). Indeed, the knowledge of these properties is still very poor, despite the great interest received by this layered phosphorus allotrope and its exfoliated 2D form, phosphorene. By combining density functional theory (DFT) calculations and solid-state NMR experiments on suspensions of fl-bP nanoflakes and on solid bP, it has been possible to characterize the 31P homonuclear dipolar and chemical shift interactions, identifying the network of 31P nuclei more strongly dipolarly coupled and highlighting two kinds of magnetically nonequivalent 31P nuclei. These results add an important missing piece of information to the fundamental chemico-physical knowledge of bP and support future extensive applications of NMR spectroscopy to the characterization of phosphorene-based materials.

Superior Photo-thermionic electron Emission from Illuminated Phosphorene Surface

This work demonstrates that black phosphorene, a two dimensional allotrope of phosphorus, has the potential to be an efficient photo-thermionic emitter. To investigate and understand the novel aspects we use a combined approach in which ab initio quantum simulation tools are utilized along with semiclassical description for the emission process. First by using density functional theory based formalism, we study the band structure of phosphorene. From the locations of electronic bands, and band edges, we estimate the Fermi level and work function. This leads us to define a valid material specific parameter space and establish a formalism for estimating thermionic electron emission current from phosphorene. Finally we demonstrate how the emission current can be enhanced substantially under the effect of photon irradiation. We observe that photoemission flux to strongly dominate over its coexisting counterpart thermionic emission flux. Anisotropy in phosphorene structure plays important role in enhancing the flux. The approach which is valid over a much wider range of parameters is successfully tested against recently performed experiments in a different context. The results open up a new possibility for application of phosphorene based thermionic and photo-thermionic energy converters.