Noncovalent Functionalization and Passivation of Black Phosphorus with Optimized Perylene Diimides for Hybrid Field Effect Transistors

Amongst the different existing methods to passivate black phosphorus (BP) from environmental degradation, the noncovalent functionalization with perylene diimides (PDI) has been postulated as one of the most promising routes because it allows preserving its electronic properties. This work describes the noncovalent functionalization and outstanding environmental protection of BP with tailor made PDI having peri-amide aromatic side chains, which include phenyl and naphthyl groups, exhibiting a significantly increased molecule-BP interaction. These results are rationalized by density functional theory (DFT) calculations showing that the adsorption energies are mainly governed by van der Waals…

Few layer 2D pnictogens catalyze the alkylation of soft nucleophiles with esters

Group 15 elements in zero oxidation state (P, As, Sb and Bi), also called pnictogens, are rarely used in catalysis due to the difficulties associated in preparing well–structured and stable materials. Here, we report on the synthesis of highly exfoliated, few layer 2D phosphorene and antimonene in zero oxidation state, suspended in an ionic liquid, with the native atoms ready to interact with external reagents while avoiding aerobic or aqueous decomposition pathways, and on their use as efficient catalysts for the alkylation of nucleophiles with esters. The few layer pnictogen material circumvents the extremely harsh reaction conditions associated to previous superacid–catalyzed alkylations…

Quantifying the Covalent Functionalization of Black Phosphorus

Abstract A straightforward quantification method to consistently determine the overall functionalization degree of covalently modified two‐dimensional (2D) black phosphorus (BP) by Raman spectroscopy has been carried out. Indeed, the successful reductive methylation of the BP lattice using sodium intercalation compounds and exhibiting different functionalization degrees has been demonstrated by 31P‐magic angle spinning (MAS) NMR spectroscopy. Furthermore, the correlation of 31P‐MAS NMR spectroscopy and statistical Raman spectroscopy (SRS) revealed the first method to determine the functionalization degree of BP solely by evaluating the intensities of distinct peaks in the Raman spectra of t…

Gitteröffnung durch reduktive kovalente Volumen‐Funktionalisierung von schwarzem Phosphor

Eine chemisch-reduktive Volumen-Funktionalisierung von dünnlagigem schwarzem Phosphor (BP) gelang unter Verwendung von BP-Interkalationsverbindungen. Durch eine effektive reduktive Aktivierung wurde die kovalente Funktionalisierung des geladenen BP mit Alkylhalogeniden erzielt, wobei eine Öffnung des BP-Gitters und ein höherer Funktionalisierungsgrad als bei neutralen Reaktionsrouten resultieren.

Liquid phase exfoliation of carbonate-intercalated layered double hydroxides.

Direct exfoliation of a carbonate layered double hydroxide (LDH) has been achieved by using a novel horn-probe sonic tip, avoiding the development of time-consuming anion-exchange reactions. The most suitable solvents were chosen based on the Hildebrand solubility parameters and the thickness of the exfoliated nanosheets confirmed unambiguously the successful delamination.

Cover Feature: Controlling the Formation of Sodium/Black Phosphorus IntercalationCompounds Towards High Sodium Content (8/2021)

Monolayer black phosphorus by sequential wetchemical surface oxidation

We report a straightforward chemical methodology for controlling the thickness of black phosphorus flakes down to the monolayer limit by layer-by-layer oxidation and thinning, using water as solubilizing agent.

Lattice Opening upon Bulk Reductive Covalent Functionalization of Black Phosphorus

The chemical bulk reductive covalent functionalization of thin-layer black phosphorus (BP) using BP intercalation compounds has been developed. Through effective reductive activation, covalent functionalization of the charged BP by reaction with organic alkyl halides is achieved. Functionalization was extensively demonstrated by means of several spectroscopic techniques and DFT calculations; the products showed higher functionalization degrees than those obtained by neutral routes.

Cover Feature: Few‐layer Black Phosphorous Catalyzes Radical Additions to Alkenes Faster than Low‐valence Metals (ChemCatChem 8/2020)

Carbon Nano-onions: Potassium Intercalation and Reductive Covalent Functionalization

Herein we report the synthesis of covalently functionalized carbon nano-onions (CNOs) via a reductive approach using unprecedented alkali-metal CNO intercalation compounds. For the first time, an in situ Raman study of the controlled intercalation process with potassium has been carried out revealing a Fano resonance in highly doped CNOs. The intercalation was further confirmed by electron energy loss spectroscopy and X-ray diffraction. Moreover, the experimental results have been rationalized with DFT calculations. Covalently functionalized CNO derivatives were synthesized by using phenyl iodide and n-hexyl iodide as electrophiles in model nucleophilic substitution reactions. The functiona…

Organic Field Effect Transistors: Noncovalent Functionalization and Passivation of Black Phosphorus with Optimized Perylene Diimides for Hybrid Field Effect Transistors (Adv. Mater. Interfaces 23/2020)

Interface Molecular engineering for laminated monolithic perovskite/silicon tandem solar cells with 80.4% fill factor

The Cluster of Excellence funded this work through “Engineering of Advanced Materials” (EAM). The authors acknowledge financial support from the DFG research-training group GRK 1896 at Erlangen University and from the Joint Project Helmholtz-Institute Erlangen Nurnberg (HI-ERN) under Project No. DBF01253, respectively. C.J.B. acknowledges the financial support through the “Aufbruch Bayern” initiative of the state of Bavaria (EnCN and Solar Factory of the Future) and the “Solar Factory of the Future” with the Energy Campus Nurnberg (EnCN). S.L. acknowledges the Real Colegio Complutense in Harvard for a research grant, and to the Spanish Ministerio de Ciencia e Innovacion for a fellowship thr…

Interface Amorphization of Two‐Dimensional Black Phosphorus upon Treatment with Diazonium Salts

Abstract Two‐dimensional (2D) black phosphorus (BP) represents one of the most appealing 2D materials due to its electronic, optical, and chemical properties. Many strategies have been pursued to face its environmental instability, covalent functionalization being one of the most promising. However, the extremely low functionalization degrees and the limitations in proving the nature of the covalent functionalization still represent challenges in many of these sheet architectures reported to date. Here we shine light on the structural evolution of 2D‐BP upon the addition of electrophilic diazonium salts. We demonstrated the absence of covalent functionalization in both the neutral and the r…

Atomically resolved TEM imaging of covalently functionalised graphene

AbstractCovalent functionalisation can be a powerful lever to tune the properties and processability of graphene. After overcoming the low chemical reactivity of graphene, covalent functionalisation led to the generation of new hybrid materials, applicable in a broad variation of fields. Although the process of functionalising graphene is nowadays firmly established, fundamental aspects of the produced hybrid materials remain to be clarified. Especially the atomically resolved imaging is only scarcely explored. Here we show aberration corrected in situ high resolution TEM imaging of dodecyl functionalised monolayer graphene at atomic resolution after an effective mechanical filtering approa…

Controlling the formation of sodium/black phosphorus intercalated compounds towards high sodium content

The solid-state synthesis of pure sodium-black phosphorus intercalation compounds (Na-BPICs) has been optimized in bulk for two stoichiometric ratios. Specifically, in-situ X-Ray diffraction (XRD) allowed the precise identification of the optimal temperature range for the formation of Na-BPICs: 94 °C–96 °C. Moreover, as the undesired formation of Na3P takes place at this very same range, we succeeded in introducing a new synthetic route based on a fast-thermal ball milling implementation that results in the bulk production of BPIC without Na3P in 9 out of 10 cases. Finally, by combining XRD, Raman spectroscopy, and DFT calculations we developed a new structural model for Na-based BPICs show…

Mechanical cleaning of graphene using in situ electron microscopy

Avoiding and removing surface contamination is a crucial task when handling specimens in any scientific experiment. This is especially true for two-dimensional materials such as graphene, which are extraordinarily affected by contamination due to their large surface area. While many efforts have been made to reduce and remove contamination from such surfaces, the issue is far from resolved. Here we report on an in situ mechanical cleaning method that enables the site-specific removal of contamination from both sides of two dimensional membranes down to atomic-scale cleanliness. Further, mechanisms of re-contamination are discussed, finding surface-diffusion to be the major factor for contam…

Controlling the Formation of Sodium/Black Phosphorus IntercalationCompounds Towards High Sodium Content

The solid-state synthesis of pure sodium-black phosphorus intercalation compounds (Na-BPICs) has been optimized in bulk for two stoichiometric ratios. Specifically, in-situ X-Ray diffraction (XRD) allowed the precise identification of the optimal temperature range for the formation of Na-BPICs: 94°C–96°C. Moreover, as the undesired formation of Na3P takes place at this very same range, we succeeded in introducing a new synthetic route based on a fast-thermal ball milling implementation that results in the bulk production of BPIC without Na3P in 9 out of 10 cases. Finally, by combining XRD, Raman spectroscopy, and DFT calculations we developed a new structural model for Na-based BPICs showin…

Alkoxide-intercalated NiFe-layered double hydroxides magnetic nanosheets as efficient water oxidation electrocatalysts

Alkoxide-intercalated NiFe-layered double hydroxides were synthesized via the nonaqueous methanolic route. These nanoplatelets exhibit high crystalline quality as demonstrated by atomic resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy. Moreover, the presence of the alkoxide moieties has been unambiguously demonstrated by means of thermogravimetric analysis coupled to a mass spectrometer. These NiFe-LDHs can be exfoliated in water or organic solvents and processed into homogeneous ultra-thin films (< 3nm thick) with the assistance of O2-plasma. The study of their behaviour as water oxidation electrocatalysts has shown an outstanding perf…

A Straightforward Approach to Multifunctional Graphene

Graphene has been covalently functionalized through a one-pot reductive pathway using graphite intercalation compounds (GICs), in particular KC8 , with three different orthogonally protected derivatives of 4-aminobenzylamine. This novel multifunctional platform exhibits excellent bulk functionalization homogeneity (Hbulk ) and degree of addition while preserving the chemical functionalities of the organic addends through different protecting groups, namely: tert-butyloxycarbonyl (Boc), benzyloxycarbonyl (Cbz) and phthalimide (Pht). We have employed (temperature-dependent) statistical Raman spectroscopy (SRS), X-ray photoelectron spectroscopy (XPS), magic angle spinning solid state 13 C NMR …

Quantifizierung der kovalenten Funktionalisierung von schwarzem Phosphor

Es wurde eine direkte Quantifizierungsmethode zur systematischen Bestimmung des Funktionalisierungsgrades von kovalent modifiziertem zweidimensionalem (2D) schwarzen Phosphor (BP) mittels Raman-Spektroskopie durchgeführt. Die erfolgreiche reduktive Methylierung des BP-Gitters mit unterschiedlichen Funktionalisierungsgraden unter Verwendung von Natrium-Interkalationsverbindungen wurde mittels 31P-MAS-Festkörper-NMR-Spektroskopie nachgewiesen. Darüber hinaus ergab die Korrelation von 31P-MAS NMR-Spektroskopie und statistischer Raman-Spektroskopie (SRS) die erste Methode zur Bestimmung des Funktionalisierungsgrades von BP allein durch die Evaluierung der Intensitätsverhältnisse bestimmter Peak…

Few-layer Black Phosphorous Catalyzes Radical Additions to Alkenes Faster than Low-valence Metals

Abstract The substitution of catalytic metals by p‐block main elements has a tremendous impact not only in the fundamentals but also in the economic and ecological fingerprint of organic reactions. Here we show that few‐layer black phosphorous (FL‐BP), a recently discovered and now readily available 2D material, catalyzes different radical additions to alkenes with an initial turnover frequency (TOF0) up to two orders of magnitude higher than representative state‐of‐the‐art metal complex catalysts at room temperature. The corresponding electron‐rich BP intercalation compound (BPIC) KP6 shows a nearly twice TOF0 increase with respect to FL‐BP. This increase in catalytic activity respect to t…

Cover Feature: Few‐layer Black Phosphorous Catalyzes Radical Additions to Alkenes Faster than Low‐valence Metals

The Cover Feature shows how phosphorene can catalyse different radical additions to alkenes. These catalysts have an initial turnover frequency up to two orders of magnitude higher than representative state–of–the–art metal complex catalysts at room temperature. In their Full Paper, M. Tejeda-Serrano et al. describe how the electron–richness of the 2D material, either phosphorene or graphene, parallels the catalytic activity of different low-valence iron compounds as metal catalysts. These results showcase the advantages of substituting metals by p–block main-group elements not only because of their positive economic and ecological fingerprint, but also because of their higher catalytic eff…