High Electron Mobility of Amorphous Red Phosphorus Thin Films

Black phosphorus (BP) has been gathering great attention for its electronic and optoelectronic applications due to its high electron mobility and high I_ON/OFF current switching ratio. The limitations of this material include its low synthetic yield and high cost. One alternative to BP is another type of phosphorus allotrope, red phosphorus (RP), which is much more affordable and easier to process. Although RP has been widely used in industry for hundreds of years and considered as an insulating material, in this study, we demonstrate through field‐effect transistors (FET) measurements that amorphous red phosphorus (a‐RP) films are semiconductive with a high mobility of 387 cm² V^?1 s^?1 and a current switching ratio of ≈10³, which is comparable to the electronic characteristics previously reported for BP. The films were produced via a thermal evaporation method or a facile drop‐casting approach onto Si/SiO₂ substrates. We also report a study of the oxidation process of the films over time and a method to stabilize the films via doping a‐RP with metal oxides. The doped films retain stability for one thousand I–V cycles, with no signs of degradation.     

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 mg_cat.^?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.     

Schwache Sn…I‐Wechselwirkungen in den Kristallstrukturen der Iodostannate [SnI4]2– und [SnI3]–

Weak Sn…I Interactions in the Crystal Structures of the Iodostannates [SnI₄]^2– and [SnI₃]^– Iodostannate complexes can be crystallized from SnI₂ solutions in polar organic solvents by precipitation with large counterions. Thereby isolated anions as well as one, two or three‐dimensional polymeric anionic substructures are established, in which SnI₃^– and SnI₄^2– groups are linked by weak Sn…I interactions. Examples are the iodostannates [Me₃N–(CH₂)₂–NMe₃][SnI₄] ( 1 ), (Ph₄P)₂[Sn₂I₆] ( 2 ), [Me₃N–(CH₂)₂–NMe₃][Sn₂I₆] ( 3 ), [Fe(dmf)₆][SnI₃]₂ ( 4 ) and (Pr₄N)[SnI₃] ( 5 ), which have been characterized by single crystal X‐ray diffraction. [Me₃N–(CH₂)₂–NMe₃][SnI₄] ( 1 ): a = 671.6(2), b = 1373.3(4), c = 2046.6(9) pm, V = 1887.7(11) · 10⁶ pm³, space group Pbcm;(Ph₄P)₂[Sn₂I₆] ( 2 ): a = 1168.05(6), b = 717.06(4), c = 3093.40(10) pm, β = 101.202(4)°, V = 2541.6(2) · 10⁶ pm³, space group P2₁/n;[Me₃N–(CH₂)₂–NMe₃][Sn₂I₆] ( 3 ): a = 695.58(4), b = 1748.30(8), c = 987.12(5) pm, β = 92.789(6)°, V = 1199.00(11) · 10⁶ pm³, space group P2₁/c;[Fe(dmf)₆][SnI₃]₂ ( 4 ): a = 884.99(8), b = 1019.04(8), c = 1218.20(8) pm, α = 92.715(7), β = 105.826(7), γ = 98.241(7), V = 1041.7(1) · 10⁶ pm³, space group P1;(Pr₄N)[SnI₃] ( 5 ): a = 912.6(2), b = 1205.1(2), c = 1885.4(3) pm, V = 2073.5(7) · 10⁶ pm³, space group P2₁2₁2₁.     

Lead and HTM Free Stable Two‐Dimensional Tin Perovskites with Suitable Band Gap for Solar Cell Applications

Organic‐inorganic hybrid perovskites have attracted great attention over the last few years as potential light‐harvesting materials for efficient and cost‐effective solar cells. However, the use of lead iodide in state‐of‐the‐art perovskite devices may demonstrate an obstacle for future commercialization due to toxicity of lead. Herein we report on the synthesis and characterization of low dimensional tin‐based perovskites. We found that the use of symmetrical imidazolium‐based cations such as benzimidazolium (Bn) and benzodiimidazolium (Bdi) allow the formation of 2D perovskites with relatively narrow band gaps compared to traditional ‐NH₃⁺ amino groups, with optical band gap values of 1.81 eV and 1.79 eV for Bn₂SnI₄ and BdiSnI₄ respectively. Furthermore, we demonstrate that the optical properties in this class of perovskites can be tuned by formation of a quasi 2D perovskite with the formula Bn₂FASn₂I₇. Additionally, we investigate the change in band gap in the mixed Sn/Pb solid solution Bn₂Sn_xPb_x?1I₄. Devices fabricated with Bn₂SnI₄ show promising efficiencies of around 2.3 %.     

Ligand Engineering Enables Efficient Pure Red Tin-Based Perovskite Light-Emitting Diodes

With increasing ecological and environmental concerns, tin (Sn)-based perovskite light-emitting diodes (PeLEDs) are competitive candidates for future displays because of their environmental friendliness, excellent photoelectric properties, and low-cost solution-processed fabrication. Nonetheless, their electroluminescence (EL) performance still lags behind that of lead (Pb)-based PeLEDs due to the fast crystallization rate of Sn-based perovskite films and undesired oxidation from Sn²⁺ to Sn⁴⁺, leading to poor film morphology and coverage, as well as high density defects. Here, we propose a ligand engineering strategy to construct high-quality phenethylammonium tin iodide (PEA₂SnI₄) perovskite films by using L-glutathione reduced (GSH) as surface ligands toward efficient pure red PEA₂SnI₄-based PeLEDs. We show that the hydrogen-bond and coordinate interactions between GSH and PEA₂SnI₄ effectively reduce the crystallization rate of the perovskites and suppress the oxidation of Sn²⁺ and formation of defects. The improved pure red perovskite films not only show excellent uniformity, density, and coverage but also exhibit enhanced optical properties and stability. Finally, state-of-the-art pure red PeLEDs achieve a record external quantum efficiency of 9.32 % in the field of PEA₂SnI₄-based devices. This work demonstrates that ligand engineering represents a feasible route to enhance the EL performance of Sn-based PeLEDs.     

Facile Conversion of Red Phosphorus into Soluble Polyphosphide Anions by Reaction with Potassium Ethoxide

Soluble polyphosphide anions were successfully generated in a number of organic solvents by the reaction between shelf‐stable red phosphorus and potassium ethoxide. The species were identified by ³¹P NMR spectroscopy in solution and by X‐ray crystal‐structure determination of (Bu₄N)₂P₁₆ in the solid state. The reaction was scaled up to gram quantities by using a flow‐chemistry process.     

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 mg_cat.⁻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.     

Surface Synergistic Protections on Red Phosphorus Anode Material by Poly(3, 4-ethylenedioxythiophene) Coating and Electrolyte Strategy in Sodium Ion Batteries

Red phosphorus has attracted more attention as a promising sodium storage material due to its ultra-high theoretical capacity and suitable sodiation potential. However, the low intrinsic electrical conductivity and large volume change of pristine red phosphorus lead to high polarization and fast capacity fading during cycling. Herein, surface synergistic protections on red phosphorus composite are successfully proposed by conductive poly(3, 4-ethylenedioxythiophene) (PEDOT) coating and electrolyte strategy. Nanoscale red phosphorus is confined in porous carbon skeleton and the outside is packaged by PEDOT coating via in-situ polymerization. Porous carbon provides rich pathways for rapid Na⁺ diffusion and empty spaces accommodate the volume expansion of red phosphorus, PEDOT coating isolates the direct contact between electrolyte and active materials to form a stable solid electrolyte interphase. In addition, the reformulated electrolyte with 3 wt% SbF₃ additives can stabilize the electrode surface and thus enhance the electrochemical performance, especially cycling stability and rate capability (433 mA·h·g^-1 at high current density of 10 A/g).     

[SnI8{Fe(CO)4}4]2+: Highly Coordinated Sn+III8 Subunit with Fragile Carbonyl Clips

[SnI₈{Fe(CO)₄}₄][Al₂Cl₇]₂ contains the [SnI₈{Fe(CO)₄}₄]²⁺ cation with an unprecedented highly coordinated, bicapped SnI₈ prism. Given the eightfold coordination with the most voluminous stable halide, it is all the more surprising that this SnI₈ arrangement is surrounded only by fragile Fe(CO)₄ groups in a clip‐like fashion. Inspite of a predominantly ionic bonding situation in [SnI₈{Fe(CO)₄}₄]²⁺, the I^????I^? distances are considerably shortened (down to 371 pm) and significantly less than the van der Waals distance (420 pm). The title compound is characterized by single‐crystal structure analysis, spectroscopic methods (EDXS, FTIR, Raman, UV/Vis, Mössbauer), thermogravimetry, and density functional theory methods.     

Structural study of C,N‐chelated monoorganotin(IV) halides

Three monoorganotin(IV) compounds of general formula L^CNSnX₃, where L^CN is a 2‐(dimethylaminomethyl)phenyl‐ group and X = Cl ( 1 ), Br ( 2 ) and I ( 3 ), were prepared and characterized using XRD and NMR techniques. Compound 1 reacts with moisture producing [(L^CN)₂HSnCl₂]⁺ [L^CNSnCl₄]^?. Compound 3 decomposes to (L^CN)₂SnI₂, SnI₂ and I₂ when heated. Compound 2 was reacted with NH₄F yielding an equilibrium of fluorine‐containing species. The major products were [L^CNSnF₅]^2? and [(L^CNSnF₃)₂(µ²‐F)₂]^2? (4a). When compound 2 was reacted with another fluorinating agent, L^CN(n‐Bu)₂SnF, an oligomeric product, [L^CNSnF₂(µ²‐F)₂]_n, was observed. Further addition of NH₄F led to subsequent formation of 4a. The structure of fluorinated products was investigated by ¹H, ¹⁹F and ¹¹⁹Sn NMR spectroscopy. Copyright © 2006 John Wiley & Sons, Ltd.     

The Cytotoxicity of Layered Black Phosphorus

Black phosphorus (BP), the latest addition to the family of 2D layered materials, has attracted much interest owing to potential optoelectronics, nanoelectronics, and biomedicine applications. Little is known about its toxicity, such as whether it could be as toxic as white phosphorus. In response to the possibility of BP employment into commercial products and biomedical devices, its cytotoxicity to human lung carcinoma epithelial cells (A549) was investigated. Following a 24 h exposure of the cells with different BP concentrations, cell viability assessments were conducted using water‐soluble tetrazolium salt (WST‐8) and methylthiazolyldiphenyltetrazolium bromide (MTT) assays. The toxicological effects were found to be dose‐dependent, with BP reducing cell viabilities to 48 % (WST‐8) and 34 % (MTT) at 50 μg mL^?1 exposure. This toxicity was observed to be generally intermediate between that of graphene oxides and exfoliated transition‐metal dichalcogenides (MoS₂, WS₂, WSe₂). The relatively low toxicity paves the way to utilization of black phosphorus.     

An Elemental Phosphorus Photocatalyst with a Record High Hydrogen Evolution Efficiency

Semiconductive property of elementary substance is an interesting and attractive phenomenon. We obtain a breakthrough that fibrous phase red phosphorus, a recent discovered modification of red phosphorus by Ruck et al., can work as a semiconductor photocatalyst for visible‐light‐driven hydrogen (H₂) evolution. Small sized fibrous phosphorus is obtained by 1) loading it on photoinactive SiO₂ fibers or by 2) smashing it ultrasonically. They display the steady hydrogen evolution rates of 633 μmol h^?1 g^?1 and 684 μmol h^?1 g^?1, respectively. These values are much higher than previous amorphous P (0.6 μmol h^?1 g^?1) and Hittorf P (1.6 μmol h^?1 g^?1). Moreover, they are the highest records in the family of elemental photocatalysts to date. This discovery is helpful for further understanding the semiconductive property of elementary substance. It is also favorable for the development of elemental photocatalysts.     

Pyridyl‐Functionalised 3H‐1,2,3,4‐Triazaphospholes: Synthesis,Coordination Chemistry and Photophysical Properties of Low‐Coordinate Phosphorus Compounds

Novel conjugated, pyridyl‐functionalised triazaphospholes with either tBu or SiMe₃ substituents at the 5‐position of the N₃PC heterocycle have been prepared by a [3+2] cycloaddition reaction and compared with structurally related, triazole‐based systems. Photoexcitation of the 2‐pyridyl‐substituted triazaphosphole gives rise to a significant fluorescence emission with a quantum yield of up to 12 %. In contrast, the all‐nitrogen triazole analogue shows no emission at all. DFT calculations indicate that the 2‐pyridyl substituted systems have a more rigid and planar structure than their 3‐ and 4‐pyridyl isomers. Time‐dependent (TD) DFT calculations show that only the 2‐pyridyl‐substituted triazaphosphole exhibits similar planar geometry, with matching conformational arrangements in the lowest energy excited state and the ground state; this helps to explain the enhanced emission intensity. The chelating P,N‐hybrid ligand forms a Re^I complex of the type [(N^N)Re(CO)₃Br] through the coordination of nitrogen atom N² to the metal centre rather than through the phosphorus donor. Both structural and spectroscopic data indicate substantial π‐accepting character of the triazaphosphole, which is again in contrast to that of the all‐nitrogen‐containing triazoles. The synthesis and photophysical properties of a new class of phosphorus‐containing extended π systems are described.     

Iodostannate(II) mit kettenförmigen [SnI3]–‐Anionen – der Übergang von fünffach zu sechsfach koordinierten SnII‐Zentralatomen

Iodostannates(II) with Anionic [SnI₃]^– Chains – the Transition from Five to Six‐coordinated Sn^II The iodostannates (Me₄N) [SnI₃] ( 1 ), [Et₃N–(CH₂)₄–NEt₃] [SnI₃]₂ ( 2 ), [EtMe₂N–(CH₂)₂–NEtMe₂] [SnI₃]₂ ( 3 ), [Me₂HN–(CH₂)₂–NH–(CH₂)₂–NMe₂H] [SnI₃]₂ ( 4 ), [Et₃N–(CH₂)₆–NEt₃] [SnI₃]₂ ( 5 ) and [Pr₃N–(CH₂)₄–NPr₃]‐ [SnI₃]₂ · 2 DMF ( 6 ) with the same composition of the anionic [SnI₃]^– chains show differences in the coordination of the Sn^II central atoms. Whereas the Sn atoms in 1 and 2 are coordinated in an approximately regular octahedral fashion, in compounds 3 – 6 the continuous transition to coordination number five in (Pr₄N) [SnI₃] ( 7 ) or [Fe(dmf)₆] [SnI₃]₂ ( 8 ) can be observed. Together with the shortening of two or three Sn–I bonds, the bonds in trans position are elongated. Thus weak, long‐range Sn…I interactions complete the distorted octahedral environment of SnI₄ groups in 3 and 4 and SnI₃ groups in 5 and 6 . Obviously the shape, size and charge of the counterions and the related cation‐anion interactions are responsible for the variants in structure and distortion.     

Die Bildungsenthalpie von SnJ4

The changes of enthalpy for the reactions

1. Sn(c)+2I₂(c)+4165 CS₂(l)=[SnI₄; 4165 CS₂] (sol.),
2. SnI₄(c)+4223 CS₂(l)=[SnI₄; 4223 CS₂] (sol.)

At 298,15 K have been found by solution calorimetry to be ΔH ₁=(?46.7±0.3) and ΔH ₂=(+3.2±0.1) kcal Mol^?1, resp. Neglecting the heat of dilution which is approximately zero these values give ΔH _f ^o (SnI₄; c; 298 K)=9?49.9±0.4) kcal Mol^?1 for the enthalpy of formation of SnI₄. From existing literature data the standard entropy is calculated to beS ^o(SnI₄; c; 298 K)=69,7 cal Mol^?1 K^?1 giving ΔG _f ^o (SnI₄; c; 298 K)=?50,5 kcal Mol^?1 for the corresponding change in theGibbs free energy.     

Isolation and Characterization of Four Phosphorus Cluster Anions P73–, P144–, P162– and P264– from the Nucleophilic Functionalization of White Phosphorus with 1,4‐Dilithio‐1,3‐butadienes

Studies on the aggregation degrees of negatively charged phosphides derived from the nucleophilic P₄ functionalization could help understand the pathway of phosphorus atoms degradation or aggregation. In this report, we have isolated and characterized four phosphorus cluster anions (P₇^3–, P₁₄^4–, P₁₆^2–, and P₂₆^4–) from the nucleophilic functionalization of P₄ with 1,4‐dilithio‐1,3‐butadienes. These phosphorus clusters could be rationalized as the P‐atom‐containing products besides the main phospholyl lithium. Their structural features and ³¹P NMR behaviors are discussed based on single crystal X‐ray diffraction analysis and ³¹P{¹H} COSY NMR analysis.     

Stable Confinement of Black Phosphorus Quantum Dots on Black Tin Oxide Nanotubes: A Robust,Double‐Active Electrocatalyst toward Efficient Nitrogen Fixation

A conceptually new, metal‐free electrocatalyst, black phosphorus (BP) is presented, which is further downsized to quantum dots (QDs) for larger surface areas, and thus, more active sites than the bulk form. However, BP QDs are prone to agglomeration, which inevitably results in the loss of active sites. Besides, their poor conductivity is not favorable for charge transport during electrolysis. To solve these problems, an electrochemically active, electrically conductive matrix, black tin oxide (SnO_2?x) nanotubes, is employed for the first time. Through facile self‐assembly, BP QDs are stably confined on the SnO_2?x nanotubes due to Sn‐P coordination, resulting in a robust, double‐active electrocatalyst. Benefiting from their synergistic superiority, the BP@SnO_2?x nanotubes deliver impressively high ammonia yield and Faradaic efficiency, which represent a successful attempt toward advanced hybrid electrocatalysts for ambient nitrogen fixation.     

A Tin Analogue of Carbenoid: Isolation and Reactivity of a Lithium Bis(imidazolin‐2‐imino)stannylenoid

The lithium bis(imino)stannylenoid (NIPr)₂Sn(Li)Cl ( 1 ; NIPr=bis(2,6‐diisopropylphenyl)imidazolin‐2‐imino) was prepared by the reaction of LiNIPr with 0.5 equiv of SnCl₂?diox (diox=1,4‐dioxane) and the ambiphilic character of the compound was demonstrated by investigations into its reactivity. Treatment of 1 with I₂ or MeI yielded the oxidative addition products (NIPr)₂SnI₂ and (NIPr)₂Sn(Me)I, respectively. In contrast, the reaction of 1 with one equivalent of Me₃SiCl resulted in the formation of Me₃SiNIPr and the chlorostannylene dimer [NIPrSnCl]₂. Moreover, the substitution reaction of compound 1 with MeLi led to the formation of the methyl‐substituted stannate (NIPr)₂Sn(Li)Me.     

On the Ambiphilic Reactivity of Geometrically Constrained Phosphorus(III) and Arsenic(III) Compounds: Insights into Their Interaction with Ionic Substrates

The ambiphilic nature of geometrically constrained Group 15 complexes bearing the N,N‐bis(3,5‐di‐tert‐butyl‐2‐phenolate)amide pincer ligand (ONO^3?) is explored. Despite their differing reactivity towards nucleophilic substrates with polarised element–hydrogen bonds (e.g., NH₃), both the phosphorus(III), P(ONO) ( 1 a ), and arsenic(III), As(ONO) ( 1 b ), compounds exhibit similar reactivity towards charged nucleophiles and electrophiles. Reactions of 1 a and 1 b with KOtBu or KNPh₂ afford anionic complexes in which the nucleophilic anion associates with the pnictogen centre ([(tBuO)Pn(ONO)]^? (Pn=P ( 2 a ), As ( 2 b )) and [(Ph₂N)Pn(ONO)]^? (Pn=P ( 3 a ), As ( 3 b )). Compound 2 a can subsequently be reacted with a proton source or benzylbromide to afford the phosphorus(V) compounds (tBuO)HP(ONO) ( 4 a ) and (tBuO)BzP(ONO) ( 5 a ), respectively, whereas analogous arsenic(V) compounds are inaccessible. Electrophilic substrates, such as HOTf and MeOTf, preferentially associate with the nitrogen atom of the ligand backbone of both 1 a and 1 b , giving rise to cationic species that can be rationalised as either ammonium salts or as amine‐stabilised phosphenium or arsenium complexes ([Pn{ON(H)O}]⁺ (Pn=P ( 6 a ), As ( 6 b )) and [Pn{ON(Me)O}]⁺ (Pn=P ( 7 a ), As ( 7 b )). Reaction of 1 a with an acid bearing a nucleophilic counteranion (such as HCl) gives rise to a phosphorus(V) compound HPCl(ONO) ( 8 a ), whereas the analogous reaction with 1 b results in the addition of HCl across one of the As?O bonds to afford ClAs{(H)ONO} ( 8 b ). Functionalisation at both the pnictogen centre and the ligand backbone is also possible by reaction of 7 a / 7 b with KOtBu, which affords the neutral species (tBuO)Pn{ON(Me)O} (Pn=P ( 9 a ), As ( 9 b )). The ambiphilic reactivity of these geometrically constrained complexes allows some insight into the mechanism of reactivity of 1 a towards small molecules, such as ammonia and water.     

Triazaphospholenium Tetrafluoroborate: A Phosphorus Analogue of a 1,2,3‐Triazole‐Derived Carbene

3H ‐1,2,3,4‐Triazaphosphole derivatives can be selectively alkylated with Meerwein's reagent at the most nucleophilic nitrogen atom. According to the principle of valence isoelectronicity, the corresponding phosphorus heterocycle represents the first formal phosphorus analogue of the well‐known 1,2,3‐triazolylidenes (mesoionic carbenes). Theoretical calculations revealed that the cation in triazaphospholenium tetrafluoroborate is an aromatic system with a high degree of π‐conjugation. First investigations showed that the cationic phosphorus heterocycle can stabilize a [Cu₂Br₄]²⁻ dianion by formation of a neutral coordination compound with an unusual bonding situation between phosphorus and copper(I).