Pyrrole Molecules Research Articles

Preparation of core-shell Si/C/graphene composite for high-performance lithium-ion battery anodes

One of the important objectives for the development of enhanced lithium-ion batteries is developing high-performance silicon-based anodes with durable operational capability. Herein, a three-dimensional graphene-decorated core-shell Si/C composite is fabricated by the in-situ polymerization of organic pyrrole molecule and pyrolysis process, in which the melamine formaldehyde resin is subtly used as three-dimensional porous framework to offer abundant loading area for the uniform dispersion of active silicon nanoparticles. Meanwhile, the core-shell structure deriving from polypyrrole in the composite can effectively buffer the volume change of silicon ingredient and avoid the direct contact with the electrolyte during the cycling process, leading to the improved structural stability and electrochemical performance. The outermost layer of graphene nanosheets is designed to enhance the electrical conductivity of the electrode. As a result, the synthesized Si/C/graphene composite exhibits a high capacity and excellent cycling performance. This work reveals that combining a three-dimensional carbon substrate with a core-shell structure might be a promising solution for anode materials with obvious volume transformation.

Multi-interface engineering design of nitrogen-doped bamboo-based carbon/Fe/Fe3C composite electromagnetic wave absorber based on honeycomb-ant nest-like structure

The integration and development of artificial intelligence (AI) and 5G communication technology have brought tremendous changes to human society. How to create a green electromagnetic environment has attracted people's attention. Rich heterostructure design based on interface engineering is considered an effective means of obtaining efficient electromagnetic wave absorbers. In this work, we have achieved innovative design of nitrogen doped carbon/Fe/Fe3C multi-interface heterostructures. The delignification modification of bamboo enriches the cellular pore channels, effectively regulates the loading of Fe3+and the diffusion binding of pyrrole molecules and promotes the deep construction of multi-layer heterogeneous interfaces. Further in-situ pyrolysis resulted in the formation of abundant honeycomb ant nest like structural pores and nitrogen doped multiphase heterostructure interfaces. Provided the best multi-component loss mechanism and impedance matching for the material, improving the overall dielectric and interface polarization effects of the material. Therefore, the obtained absorbent exhibits satisfactory electromagnetic wave absorption performance at a low load of 20 %, with an effective absorption bandwidth of 6.5 GHz (1.85 mm). This work provides new ideas for the high-value utilization of biomass in nature, optimization and innovative design of multi-level pore structures for microwave absorbers.

Atomic-Level Insights of Polypyrrole Grafted InGaZnO Structure for ppb-Level Ozone Gas Sensing at Low Operating Temperature.

This study explores the utilization of the organic conductive molecule Polypyrrole (PPy) for the modification of Indium Gallium Zinc Oxide (IGZO) nanoparticles, aiming to develop highly sensitive ozone sensors. Pyrrole (Py) molecules undergo polymerization, resulting in the formation of extended chains of PPy that graft onto the surface of IGZO nanoparticles. This interaction effectively diminishes oxygen vacancies on the IGZO surface, thereby promoting the crystallization of the IGZO (1114) facets. The resultant structure exhibits promising potential for achieving high-performance wideband semiconductor gas sensors. The IGZO/PPy device forms a Straddling Gap heterojunction, facilitating enhanced electron transfer between IGZO and ozone molecules. Notably, the adsorption and desorption of ozone gas occur efficiently at a low temperature of approximately 25 °C, obviating the need for additional energy typically associated with wide bandgap semiconductor materials. Density Functional Theory (DFT) calculations attribute this efficiency to the enhanced number of active sites for ozone adsorption, facilitated by hydrogen bonds. The substantial conductivity of PPy, combined with its planar ring structure, induces positively charged polarization on the IGZO side upon ozone adsorption. The resultant device exhibits exceptional sensitivity, boasting a 4-fold improvement compared to sensors reliant solely on IGZO. Additionally, the response time is significantly reduced by a factor of 10, underscoring the practical viability and enhanced performance of the IGZO/PPy sensor field.

Direct Probe of Conical Intersection Photochemistry by Time-Resolved X-ray Magnetic Circular Dichroism.

The direct probing of photochemical dynamics by detecting the electronic coherence generated during passage through conical intersections is an intriguing challenge. The weak coherence signal and the difficulty in preparing purely excited wave packets that exclude coherence from other sources make it experimentally challenging. We propose to use time-resolved X-ray magnetic circular dichroism to probe the wave packet dynamics around the conical intersection. The magnetic field amplifies the relative strength of the electronic coherence signal compared to populations through the magnetic field response anisotropy. More importantly, since the excited state relaxation through conical intersections involves a change of parity, the magnetic coupling matches the symmetry of the response function with the electronic coherence, making the coherence signal only sensitive to the conical intersection induced coherence and excludes the pump pulse induced coherence between the ground state and excited state. In this theoretical study, we apply this technique to the photodissociation dynamics of a pyrrole molecule and demonstrate its capability of probing electronic coherence at a conical intersection as well as population transfer. We demonstrate that a magnetic field can be effectively used to extract novel information about electron and nuclear molecular dynamics.

Conformal and conductive biofilm-bridged artificial Z-scheme system for visible light-driven overall water splitting.

Semi-artificial Z-scheme systems offer promising potential toward efficient solar-to-chemical conversion, yet sustainable and stable designs are currently lacking. Here, we developed a sustainable hybrid Z-scheme system capable for visible light-driven overall water splitting by integrating the durability of inorganic photocatalysts with the interfacial adhesion and regenerative property of bacterial biofilms. The Z-scheme configuration is fabricated by drop casting a mixture of photocatalysts onto a glass plate, followed by the growth of biofilms for conformal conductive paste through oxidative polymerization of pyrrole molecules. Notably, the system exhibited scalability indicated by consistent catalytic efficiency across various sheet areas, resistance observed by remarkable maintaining of photocatalytic efficiency across a range of background pressures, and high stability as evidenced by minimal decay of photocatalytic efficiency after 100-hour reaction. Our work thus provides a promising avenue toward sustainable and high-efficiency artificial photosynthesis, contributing to the broader goal of sustainable energy solutions.

Elastic and Electronically Inelastic Cross Sections for the Scattering of Electrons by Pyrrole.

Integral and differential cross sections for elastic and electronically inelastic electron scattering from the pyrrole molecule are reported. The cross section calculations employed the Schwinger multichannel method with norm-conserving pseudopotentials. The collision dynamics was described according to a model in which up to 209 energetically accessible channels were treated as open. In the elastic channel, calculations carried out in the interval of energies from 0 to 50 eV revealed the presence of four resonances with peaks located at 2.56 eV (π1*), 3.82 eV (π2*), 4.70 eV (σNH*), and between 8.30 and 9.50 eV (σ*) positions which are in good agreement with previous assignments. Moreover, the role of the multichannel coupling effects in obtaining accurate cross sections was evaluated by comparing the present results with theoretical results recently reported in the literature and early measurements performed for elastic electron collisions with furan. Electronic excitation cross sections involving the transitions from ground state to the 13B2, 13A1, 11A2, and 11A1 excited states of pyrrole driven by electron impact are presented for energies from thresholds up to 50 eV and, whenever possible, critically compared with the data available in the literature.

Substituent effect on the electronic and optical properties of newly designed pyrrole derivatives using density functional theory

Abstract This work explores six newly designed compounds obtained by several substitutions in 2,5-di(2-thienyl) pyrrole molecule. For this series of compounds, the electronic and optical properties were investigated using density functional theory and time-dependent density functional theory (TD-DFT). The new compounds were characterized by calculating the chemical parameters that correlated with their optical and electrical properties. The lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) energies are calculated using the B3LYP functional with the 6-311G (d, p) basis set. The most low-lying energy level of the LUMO was found for Perr-NO2, indicating its effective electron injection capabilities and oxidation resistance. The HOMO and LUMO distributions of Perr-Cl and Perr-NO2 displayed a remarkable complementarity throughout each component of the two compounds, indicating an effective intermolecular charge transfer. The molecular electrostatic potential analysis demonstrated that the proposed compounds have a broad distribution of electrophilic and nucleophilic sites, which predict a high degree of chemical reactivity. The electron density analysis at the bonding and anti-bonding sites of the title compounds was performed using the electron localization function and local orbital locator techniques. Non-covalent interaction analysis using the reduced density gradient approach classified all types of interaction: repulsive, weak, and attractive interactions within compound fragments. All compounds exhibited a robust repulsive interaction, as proved by the red spikes at 0.038 a.u. The ultraviolet/visible (UV/vis) spectrum was obtained by TD-DFT using CAM-B3LYP models in conjunction with 6-311G (d, p) basis set and methanol as a solvent, the absorption bands were found within the UV range, and the maximum wavelength showed red-shifted increases. These compounds could serve as a base material for developing selective gas sensors with considerable UV/vis absorption (180–400 nm). According to the research results, the designed compounds are good candidates for use as precursors in polymer designs for optoelectronic and sensor applications due to their high electrical conductivity and photochemical properties.

Probing the Electronic Structure of [B10H10]2- Dianion Encapsulated by an Octamethylcalix[4]pyrrole Molecule.

Despite being an important closo-borate in condensed phase boron chemistry, isolated [B10H10]2- is electronically unstable and has never been detected in the gas phase. Herein, we report a successful capture of this fleeting species through binding with an octamethylcalix[4]pyrrole (omC4P) molecule to form a stable gaseous omC4P·[B10H10]2- complex and its characterizations utilizing negative ion photoelectron spectroscopy (NIPES). The recorded NIPE spectrum, contributed by both omC4P and [B10H10]2-, is deconvoluted by subtracting the omC4P contribution to yield a [B10H10]2- spectrum. The obtained [B10H10]2- spectrum consists of four major bands spanning the electron binding energy (EBE) range from 1 to 5 eV, with the EBE gaps matching excellently with the energy intervals of computed high-lying occupied molecular orbitals of the [B10H10]2- dianion. This study showcases a generic method to utilize omC4P to capture unstable multiply charged anions in the gas phase for experimental determination of their electronic structures.

Quantum tomography of molecules using ultrafast electron diffraction.

We propose a quantum tomography (QT) approach to retrieve the temporally evolving reduced density matrix in electronic state basis, where the populations and coherence between the ground state and excited state are reconstructed from the ultrafast electron diffraction signal. In order to showcase the capability of the proposed QT approach, we simulate the nuclear wavepacket dynamics and ultrafast electron diffraction of photoexcited pyrrole molecules using the abinitio quantum chemical CASSCF method. From the simulated time-resolved diffraction data, we retrieve the evolving density matrix in a crude diabatic representation basis and reveal the symmetry of the excited pyrrole wavepacket. Our QT approach opens the route to make a quantum version of "molecular movie" that covers the electronic degree of freedom and equips ultrafast electron diffraction with the power to reveal the coherence between electronic states, relaxation, and dynamics of population transfer.

Precursor design and cascade mechanism of RuO2·xH2O atomic layer deposition

As the unique nanofabrication technique, atomic layer deposition (ALD) can be used to deposit high-quality, uniform, and conformal nanoparticle coatings. Ru and its oxides (RuOx) are important materials in the fields of microelectronics and catalysis. In this work, the reaction of Ru precursors with different ligands on the hydroxylated surfaces were explored. The elimination of the pyrrolyl (Py) ligand is easier than that of the cyclopentadienyl (Py) ligand on the hydroxylated surface. The reaction involved in RuO2·xH2O ALD using RuPy2 and H2O as precursors was further investigated. During the RuPy2 reaction, the pyrrolyl ligand is eliminated by the substitution reaction with a surface hydroxyl group. However, the desorption of the pyrrole molecule is difficult due to the strong adsorption between the pyrrole molecule and Ru surface. During the H2O reaction, the H2O molecules further help the elimination of pyrrolyl ligands from the surface and the dissociative desorption of pyrrole molecules This unique reaction mechanism involved in the ALD of RuO2 with the assistance of H2O can be termed new cascade mechanism. These findings provide theoretical guidance for precursor design and ALD growth of metal oxides.

Synthesis of 1,2,5-substituted pyrrole derivatives by a modification of the Reisch-Schulte reaction

A synthesis method was developed for the formation of several 1,2,5-substituted pyrrole derivatives and were characterized by NMR, IR, UV–Vis spectroscopies and HRMS. This method involves adding aniline derivatives to a dialkyne, catalyzed by Cu(I) and is carried out under modified Reisch-Schulte protocol by adding N,N,N′,N′-tetramethylethylenediamine (TMEDA). Notably, the reaction does not proceed in absence of TMEDA. The yields of synthesized pyrroles ranged from quantitative to acceptable ones. Generally, the reaction yields correlated well with the Global nucleophilicities (GN) of the aniline reagents obtained from theoretical calculations; more nucleophilic anilines resulted in higher yields, except para-anisidine, the molecule with the biggest GN value. Mechanistic explications of the observed effects were proposed. Additionally, experimental studies and theoretical simulation showed that the novel pyrrole molecules had semiconducting properties since their band gap energy (Eg) lied within the range typical for organic semiconductors. It was observed that the presence of electron-withdrawing groups led to a significant decrease in the Eg value.

Catalytic Degradation of Triphenylmethane Dyes with an Iron Porphyrin Complex as a Cytochrome P450 Model.

The organic dyes used in printing and dyeing wastewater have complex components, diverse structures and strong chemical stability, which make them not suitable for treatment and difficult to degrade in the environment. Porphyrins are macromolecules with 18 π electrons formed by four pyrrole molecules connected with a methylene bridge that has a stable structure. Porphyrin combines with iron to form an active intermediate with a structure similar to the cytochrome P450 enzyme, so they are widely used in the biomimetic field. In the current study, 5,10,15,20-tetra (4-carboxyphenyl) porphine ferric chloride (III) (Fe(III)TCPP) was used as a catalyst and iodosobenzene was used as an oxidant to explore the catalytic degradation of triphenylmethane dyes, such as rhodamine B (RhB) and malachite green (MG). The results of UV-Vis spectral analysis have shown that the conversion rate of the rhodamine B was over 90% when the amount of Fe(III)TCPP was 0.027 mM and the amount of iodosobenzene was eight equivalents. When the catalyst was 0.00681 mM and the amount of the oxidant was five equivalents, the conversion rate of the malachite green reached over 95%. This work provides a feasible method for the degradation of triphenylmethane dyes.

A controllably fabricated polypyrrole nanorods network by doping a tetra-β-carboxylate cobalt phthalocyanine tetrasodium salt for enhanced ammonia sensing at room temperature.

The morphology adjustment and functional doping optimization of polypyrrole (PPy) are of great significance in improving its gas sensing performance. Here, the PPy-0.5TcCoPc nanorods with a uniform dispersed 3-D network were prepared using one-step in situ polymerization using the electrostatic interaction between dopant counterion substituents in tetra-β-carboxylate cobalt phthalocyanine tetrasodium salt (TcCoPcTs) with larger space structure and pyrrole (Py) molecules, in which TcCoPcTs is not only used as a dopant molecule crosslinking PPy chains to obtain a 3-D network, thus improving the conductivity, but also as a sensor accelerator to improve the gas-sensing performance. The resulting PPy-TcCoPc hybrid exhibits superior NH3-sensing properties than PPy and tetra-β-carboxylate cobalt phthalocyanine (TcCoPc) under the same test conditions, especially the PPy-0.5TcCoPc sensor shows ultrafast response/recovery time to 50 ppm NH3 (8.1 s/370.8 s), low detection limit of 8.1 ppb and excellent gas selectivity at room temperature (20 °C). Besides, the PPy-0.5TcCoPc sensor also maintains superior response (49.3% to 50 ppm NH3), humidity resistance and conspicuous stability over 45 days. The excellent NH3-sensing performance of the PPy-0.5TcCoPc hybrid arises from the excellent gas selectivity of TcCoPc, the remarkable response mechanism between PPy and NH3, the high electrical conductivity, abundant active sites and good electron transport ability of the unique 3-D network with large specific surface area. The morphology regulation and functional doping optimization strategy of TcCoPcTs doped PPy broaden the research direction of ideal gas sensor materials.

A density functional study of the coronene-pyrrole system in relation to its possible application as NO2 and NH3 sensors

According to recent research on the application of graphene materials as sensors and particularly polypyrrole-graphene materials, which are especially promising, the functionalization of graphene with a pyrrole molecule might be considered a viable alternative as a NO2 and NH3 sensor. In this way, a graphene sheet simulated as a coronene molecule was used in order to test whether this kind of functionalization could be useful for detecting the NO2 and NH3 toxic gases with a relatively high sensitivity. NO2 was studied as an example of an electron acceptor molecule, and NH3 as an electron donor molecule. Both molecules were adsorbed on two different regions of the functionalized adsorbent, and the energy ranges found for adsorption were reported and compared with those of the pristine graphene. The results indicated that in the coronene-pyrrole system, pyrrole tends to lie almost parallel to the coronene sheet in a π-π stacking interaction between the two conjugated systems, being the closest distances of 3.0 and 3.2 Å. The use of Δ (ΔHOMO-LUMO) as a descriptor confirmed that the coronene-pyrrole system is a good option as a NO2- and NH3-sensor; therefore, it might be an easy and suitable descriptor for characterizing the performance of a sensor; all calculations were made using a Density Functional formalism, through a functional M06-2X in combination with the 6-31G(d,p) basis set.

Distant Symmetry Control in Electron-Induced Bond Cleavage.

We experimentally show that N-H bond cleavage in the pyrrole molecule following resonant electron attachment is allowed and controlled by the motion of the atoms which are not dissociating, namely, of the carbon-attached hydrogen atoms. We use this fact to steer the efficiency of this bond cleavage. In order to interpret the experimental findings, we have developed a method for locating all resonant and virtual states of an electron-molecule system in the complex plane, based on all-electron R-matrix scattering calculations. Mapping these as a function of molecular geometry allows us to separate two contributing dissociation mechanisms: a π* resonance formation inducing strong bending deformations and a nonresonant σ* mechanism originating in a virtual state. The coupling between the two mechanisms is enabled by the out-of-plane motion of the C-H bonds, and we show that it must happen on an ultrafast (few fs) time scale.

Novel co-polymerization of polypyrrole/polyaniline on ferrate modified biochar composites for the efficient adsorption of hexavalent chromium in water.

It is still a huge challenge to prepare cheap and effective composite materials for removing hexavalent chromium (Cr(VI)) in sewage treatment. In this study, a noval co-polymerization of polypyrrole/polyaniline on ferrate modified biochar (Ppy/PANI/FBC) was fabricated via ferrate-promoted pyrolysis and in-situ oxidative polymerization of pyrrole and aniline molecules to effectively remove Cr(VI) from polluted water. The Ppy/PANI/FBC quickly decreased Cr(VI) concentration from 38.92 to 3.92mg/L within 400min, with an efficient removal efficiency (89.92%), which was significantly higher than that of FBC (4.75%), Ppy/FBC (72.30%), and PANI/FBC (42.43%). These results are mainly caused by its conjugated connection and well-dispersion of Ppy and PANI on the surface of a carbon-based material. Meanwhile, the experimental results were in line with the pseudo-second-order kinetic and Freundlich models. The Ppy/PANI/FBC is featured by a high capacity of Cr(VI) adsorption (up to 203.71mg/g). In addition, it could be adopted for efficiently removing Cr(VI) over a wide pH range (4-9) because of the positively charged nitrogen (-NH.+- and=N+-). The sorption mechanisms of Cr(VI) were identified, including electrostatic interaction with surface protonated nitrogen (N+), ion exchange between the doped Cl- ions and Cr(VI), chemical decrease of the Cr(VI) to Cr(III) by the iron valence cycle and efficient electron transfer of Ppy/PANI/FBC, as well as surface complexation by amine and oxygen-containing groups. More importantly, 97.98% Cr(VI) was efficiently removed in 20min by coupling a photocatalytic reaction, also providing a novel idea for the practical use of adsorbents in wastewater treatment.

The First Example of Photogeneration of a Pyrrole Molecule on the Basis of 6π-Electrocyclization of 2-Arylbenzofurans Containing a Pyrazole Fragment

The photochemical behavior of terarylenes containing benzofuran and aminopyrazole fragments was studied. It was found that the presence of an amino group in the structure of the studied terarylenes blocks photocyclization. At the same time, the transformation of the amino group into a pyrrole fragment allows one to remove the aforementioned blocking effect. As a result, UV-irradiation of pyrrole-containing compounds leads to 6π-electrocyclization of the 1,3,5-hexatriene system with the formation of polycyclic molecules. For the first time an efficient method for the photogeneration of pyrrole molecule using the phototransformation of substituted 2-arylbenzofurans was proposed. The structure of one of the target products was established by X-ray diffraction.

Modulation of the spin transport properties of γ-graphyne by chemical anchoring groups and strain

Chemical anchoring groups can modulate the connection between metal electrode surfaces and central molecules and regulate the distribution of electronic states and charge transport in monomolecular device energy levels. Thus, the introduction of different anchoring groups inevitably has an influence on multifunctional molecular devices. Moreover, the strain effect is also an important method for electronic property modulation of two-dimensional materials. Therefore, in this paper, three different chemical anchoring groups are combined with compressive and tensile strains, aiming for dual-modulation behavior in the spin-resolved transport properties of γ-graphyne molecular devices. Our calculation results suggest that the chemical anchoring groups of pyrrole (C4H5N), thiophene (C4H4S), and 1H-phosphole (C4H5P) molecules combined with strain have a good regulatory effect on the transport of designed molecular devices, which can be seen from the transmission spectra and molecular energy spectrum. In addition, the dual modulation can induce the spin-polarization phenomenon and the maximum spin filtering efficiency reaches 90%. Furthermore, negative differential resistance behavior has been achieved in the proposed device, and the maximum peak-to-valley ratio can reach 12.14. Our findings may provide a theoretical basis for the dual modulation of molecular junctions by chemical anchoring groups and strain for future nanoelectronic devices.

Simulation of the dynamics of vibrationally mediated photodissociation for deuterated pyrrole

The dynamics of photodissociation for vibrationally pre-excited deuterated pyrrole molecules is simulated using ab initio multiple cloning (AIMC) approach. Total kinetic energy release (TKER) spectra and dissociation times are calculated. The results for pyrrole and deuterated pyrrole molecules with and without vibrational pre-excitation are compared. Calculations show that, as expected, the kinetic energy of additional dissociation fragments is lower in deuterated pyrrole and mostly located in the upper-middle part of the TKER spectrum. However, despite lower energy of dissociative bond vibrations, pre-excitation of deuterated pyrrole leads to higher dissociation yield increase than in pyrrole and significantly shortens dissociation time.

Density functional theory investigation to surface modification of boron nitride nanotubes.

We studied the boron nitride nanotube (BNNT) modification through pyrrole molecule properties by implementing B3LYP and M06-2X methods. The results of DFT show that the pyrrole molecule has a strong interaction with BNNT, showing that its adsorption onto the nanotube surface is corresponding to chemical functionalization. Also, after the chemical modification, density of states shows that there is a slight modification in the BNNT electronic properties. Furthermore, electrical conductivity of functionalized BNNT (f-BNNT) was increased compared to BNNT, which shows that an increase in the electron-donating nature of functional groups increases the functionalization energy. Maintaining the BNNT electronic properties along with the improved solubility gives us an idea that BNNT chemical modification through pyrrole can affect the way BNNTs are purified.