scholarly journals Modulating Electronic Properties of Dinitrosoarene Polymers

2021 ◽  
Author(s):  
Lujo Matasović ◽  
Barbara Panić ◽  
Matej Bubaš ◽  
Hrvoj Vančik ◽  
Ivana Biljan ◽  
...  
Keyword(s):  
Transport Properties ◽  
Band Gap ◽  
Diffuse Reflectance Spectroscopy ◽  
Gold Surface ◽  
Binding Energies ◽  
Organic Polymer ◽  
Torsional Angle ◽  
Coulombic Interaction ◽  
Force Microscopy ◽  
Td Dft

We present a comprehensive analysis on how the electronic structure and the optical properties of an organic polymer can be modulated, based on the example of the dinitrosobenzene polymer (1). Using a combination of computational and experimental tools, we explore the effects of solid-state packing, backbone torsion, surface adsorption, the conjugation in the aromatic core, and substituents. The band gap (Eg) and optical spectrum of 1 are calculated using both GW-BSE with zero-gap renormalization (ZGR) and hybrid TD-DFT, with the former method predicting a value (2.41 eV) in excellent agreement with our diffuse reflectance spectroscopy measurements (2.39 eV). Using GW-BSE-ZGR, changes occurring upon solidstate packing are separated into a contribution arising from (i) the change in the torsional angle and (ii) the change in the screened Coulombic interaction, which strongly effects the exciton binding energies. Comprehensive hybrid TD-DFT calculations find that the effects of substituents on Eg and on transport properties can mostly be explained through changes in the torsional angle, and predict a linear dependence between it and Eg. Extending the conjugation in the aromatic core is found to enhance transport properties and narrow Eg, identifying future synthetic targets. Atomic force microscopy and spectroscopic ellipsometry are used to study 1 adsorbed to a (111) gold surface (1@Au), with the latter method showing a significant narrowing of the band gap to 0.68 eV, in good agreement with TD-DFT predictions.

scholarly journals Modulating Electronic Properties of Dinitrosoarene Polymers

2021 ◽  
Author(s):  
Lujo Matasović ◽  
Barbara Panić ◽  
Matej Bubaš ◽  
Hrvoj Vančik ◽  
Ivana Biljan ◽  
...  
Keyword(s):  
Transport Properties ◽  
Band Gap ◽  
Diffuse Reflectance Spectroscopy ◽  
Zero Point ◽  
Gold Surface ◽  
Binding Energies ◽  
Force Microscopy ◽  
Atomic Force ◽  
A Value ◽  
Td Dft

The possibilities for tuning of electronic, transport, and optical properties of the linear dinitrosobenzene polymer (1) are explored. The band gap (Eg) and optical spectrum of 1 are calculated using both GW-BSE corrected for zero-point vibrations and hybrid TD-DFT, with the former method predicting a value (2.41 eV) in excellent agreement with diffuse reflectance spectroscopy measurements (2.39 eV). GW-BSE is also used to evaluate the effects of solid-state packing, while comprehensive TD-DFT calculations are employed to study the effects of intra-polymer torsion, gold surface adsorption, substitution, and changes in the aromatic core of 1. Torsion is found to be an important factor in determining Eg and transport properties, and a strong effect of the environment on the exciton binding energies is identified. Extending the conjugation in the aromatic core is found to enhance transport properties and narrow Eg, identifying future synthetic targets. Atomic force microscopy and spectroscopic ellipsometry are used to study 1 adsorbed to a (111) gold surface (1@Au), with the latter method showing a significant narrowing of the band gap to 0.68 eV, in good agreement with TD-DFT predictions.

scholarly journals On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons

Nano Research ◽  
2021 ◽  
Author(s):  
Xiushang Xu ◽  
Marco Di Giovannantonio ◽  
José I. Urgel ◽  
Carlo A. Pignedoli ◽  
Pascal Ruffieux ◽  
...  
Keyword(s):  
Carbon Nanomaterials ◽  
Graphene Nanoribbons ◽  
Gold Surface ◽  
Fine Tuning ◽  
Uniform Structure ◽  
Methyl Groups ◽  
Structural Modifications ◽  
Force Microscopy ◽  
Chemical Structures ◽  
Atomic Force

AbstractGraphene nanoribbons (GNRs) have potential for applications in electronic devices. A key issue, thereby, is the fine-tuning of their electronic characteristics, which can be achieved through subtle structural modifications. These are not limited to the conventional armchair, zigzag, and cove edges, but also possible through incorporation of non-hexagonal rings. On-surface synthesis enables the fabrication and visualization of GNRs with atomically precise chemical structures, but strategies for the incorporation of non-hexagonal rings have been underexplored. Herein, we describe the on-surface synthesis of armchair-edged GNRs with incorporated five-membered rings through the C-H activation and cyclization of benzylic methyl groups. Ortho-Tolyl-substituted dibromobianthryl was employed as the precursor monomer, and visualization of the resulting structures after annealing at 300 °C on a gold surface by high-resolution noncontact atomic force microscopy clearly revealed the formation of methylene-bridged pentagons at the GNR edges. These persisted after annealing at 340 °C, along with a few fully conjugated pentagons having singly-hydrogenated apexes. The benzylic methyl groups could also migrate or cleave-off, resulting in defects lacking the five-membered rings. Moreover, unexpected and unique structural rearrangements, including the formation of embedded heptagons, were observed. Despite the coexistence of different reaction pathways that hamper selective synthesis of a uniform structure, our results provide novel insights into on-surface reactions en route to functional, non-benzenoid carbon nanomaterials.

Enhanced visible-active photocatalytic behaviors observed in Mn-doped BiFeO3

2018 ◽  
Vol 32 (17) ◽  
pp. 1850185 ◽  
Author(s):  
Yun-Hui Si ◽  
Yu Xia ◽  
Ya-Yun Li ◽  
Shao-Ke Shang ◽  
Xin-Bo Xiong ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Band Gap ◽  
Diffuse Reflectance Spectroscopy ◽  
X Ray Diffraction ◽  
Electron Hole ◽  
X Ray ◽  
Mn Doped ◽  
Hole Recombination ◽  
Narrow Band Gap Semiconductors

A series of BiFeO3 and BiFe[Formula: see text]Mn[Formula: see text]O3 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) were synthesized by a hydrothermal method. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS) and UV–Vis diffuse reflectance spectroscopy, and their photocatalytic activity was studied by photocatalytic degradation of methylene blue in aqueous solution under visible light irradiation. The band gap of BiFeO3 was significantly decreased from 2.26 eV to 1.90 eV with the doping of Mn. Furthermore, the 6% Mn-doped BiFeO3 photocatalyst exhibited the best activity with a degradation rate of 94% after irradiation for 100 min. The enhanced photocatalytic activity with Mn doping could be attributed to the enhanced optical absorption, increment of surface reactive sites and reduction of electron–hole recombination. Our results may be conducive to design more efficient photocatalysts responsive to visible light among narrow band gap semiconductors.

Atomistic Calculations of Dopant Binding Energies in ZnGeP2

1997 ◽  
Vol 484 ◽  
Author(s):  
Ravindra Pandey ◽  
Melvin C. Ohmer ◽  
A. Costales ◽  
J. M. Recio
Keyword(s):  
Experimental Data ◽  
Band Gap ◽  
Interatomic Potential ◽  
Host Lattice ◽  
Binding Energies ◽  
First Principle ◽  
Atomistic Model ◽  
Group Iii ◽  
Atomistic Calculations

AbstractAtomistic model has been applied to study various cation dopants, namely Cu, Ag, B, Al, Ga and In in ZnGeP2. The pairwise interatomic potential terms representing the interaction of dopants with the host lattice ions are derived using first principle methods. Defect calculations based on Mott-Littleton methodology predict small binding energies for Cu and Ag substituting Zn in the lattice which are in agreement with the available experimental data. The group III dopants (i.e. B, Al, Ga and In) at the Ge site are predicted to have large binding energies for a hole except B which shows a distinct behavior. This may be due to large mismatch in atomic sizes of B and Ge. At the Zn site, the calculated binding energies of the group III dopants place donor levels in the middle of the band gap.

scholarly journals Фотофизические свойства тонких пленок перилена, модифицированного функциональными группами диангидрида и диимида тетракарбоновой кислоты

2021 ◽  
Vol 63 (9) ◽  
pp. 1437
Author(s):  
А.С. Комолов ◽  
Э.Ф. Лазнева ◽  
Е.В. Жижин ◽  
Э.К. Алиджанов ◽  
Ю.Д. Лантух ◽  
...  
Keyword(s):  
Charge Carrier ◽  
Band Gap ◽  
Charge Carrier Mobility ◽  
Dark Conductivity ◽  
Localized States ◽  
Semiconductor Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After ◽  
Carrier Traps

The morphology of organic semiconductor films of perylenetetracarboxylic acid dianhydride (PTCDA) and perylenetetracarboxylic acid dibenzyl-diimide (N, N`-DBPTCDI) formed by thermal vacuum deposition was studied by atomic force microscopy. It was shown that annealing of films at 420 K leads to rearrangement of their structure and crystallization. The optical absorption spectra of the films under study were used to estimate the optical band gap. The temperature dependence of the dark conductivity of PTCDA and N, N-DBPTCDI films before and after annealing (Т = 420 K) was established. The values of the activation energy of charge carrier traps are determined. The computer simulation of the density of localized states in the band gap of the films studied was carried out using the photoconductivity spectra in the constant photocurrent mode. Model photovoltaic cells based on PTCDA / СuPc and N, N-DBPTCDI / СuPc structures were formed. The kinetics of decay of the interfacial photo-voltage of the cells prepared was measured using pulsed light as an excitation source. On the basis of the performed measurements, the charge carrier mobility values in the investigated semiconductor materials were estimated.

scholarly journals Improved Understanding of the Sulfidization Mechanism in Amine Flotation of Smithsonite: An XPS, AFM and UV–Vis DRS Study

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 370 ◽  
Author(s):  
Ruizeng Liu ◽  
Bin Pei ◽  
Zhicheng Liu ◽  
Yunwei Wang ◽  
Jialei Li ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
High Reactivity ◽  
Phase Imaging ◽  
Solid Product ◽  
Force Microscopy ◽  
Atomic Force ◽  
Liquid Reaction ◽  
Solid Liquid ◽  
Heterogeneous Solid

Sulfidization is required in the amine flotation of smithsonite; however, the sulfidization mechanism of smithsonite is still not fully understood. In this work, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) were used to characterize sulfidized and unsulfidized smithsonite. The XPS and UV–vis DRS analyses showed that smithsonite sulfidization is a transformation of ZnCO3 to ZnS on the smithsonite surfaces. However, this transformation is localized, resulting in the coexistence of ZnCO3 and ZnS or in the formation of ZnS island structures on the sulfidized smithsonite surfaces. AFM height imaging showed that sulfidization can substantially change the surface morphology of smithsonite; in addition, AFM phase imaging demonstrated that sulfidization occurs locally on the smithsonite surfaces. Based on our findings, it can be concluded that smithsonite sulfidization is clearly a heterogeneous solid–liquid reaction in which the solid product attaches at the surfaces of unreacted smithsonite. Smithsonite sulfidization involves heterogeneous nucleation and growth of ZnS nuclei. Moreover, the ZnS might nucleate and grow preferentially in the regions with high reactivity, which might account for the formation of ZnS island structures. In addition, sphalerite-structured ZnS is more likely to be the sulfidization product of smithsonite under flotation-relevantconditions, as also demonstrated by the results of our UV–vis DRS analyses. The results of this study can provide deeper insights into the sulfidization mechanism of smithsonite.

Ab-initio calculations on the structural and electronic transport properties of five-atom GaN clusters

2019 ◽  
Vol 33 (29) ◽  
pp. 1950347 ◽  
Author(s):  
Xiao-Chong Liang ◽  
Xiao-Jiang Long ◽  
Lin Zhang ◽  
Jun Zhu
Keyword(s):  
Transport Properties ◽  
Electronic Transport ◽  
Density Functional ◽  
Differential Resistance ◽  
Pso Algorithm ◽  
Binding Energies ◽  
Functional Theory ◽  
Swarm Optimization ◽  
Electronic Transport Properties ◽  
Stable Structures

The structural and electronic transport properties of [Formula: see text] clusters are studied based on density functional theory (DFT). Their most stable structures are proved to be planar by the particle swarm optimization (PSO) algorithm, and have decreasing binding energies with the increasing number of Ga atom in clusters. The electronic transport properties of these clusters connected with two Al(1 0 0) electrodes are calculated by combining nonequilibrium Green’s-function (NEGF) with DFT. Most of them have an equilibrium conductance of above [Formula: see text], except for [Formula: see text]. Negative differential resistance (NDR) phenomenon of different level is observed in their I–V curves in bias ranges of from [Formula: see text] to [Formula: see text] V and from 0.7 to 1.1 V.

DEPOSITION OF WIDE BAND GAP DLC FILMS USING R.F. PECVD AT VERY LOW POWER

2011 ◽  
Vol 25 (29) ◽  
pp. 3941-3949 ◽  
Author(s):  
P. K. BARHAI ◽  
RISHI SHARMA ◽  
B. B. NAYAK
Keyword(s):  
Band Gap ◽  
Chemical Vapor ◽  
Wide Band ◽  
Carbon Films ◽  
Wide Band Gap ◽  
Force Microscopy ◽  
Atomic Force ◽  
Frequency Plasma ◽  
Bending Modes ◽  
Deposited Films

Wide band gap diamond-like carbon films (DLCs) are deposited on silicon (1 0 0) substrates using capacitive coupled radio frequency plasma-enhanced chemical vapor deposition (R.F. PECVD) technique. The deposition of films is carried out at a constant pressure (~5×10-2 mbar ) using acetylene precursor diluted with argon at constant R.F. power of 5 W. Raman spectroscopy of deposited DLC films shows broad G peak near 1550 cm-1 and a weak D peak near 1320 cm1. FTIR plot of DLC films shows a peak near 2900 cm-1 corresponding to C–H stretching mode and peaks below 2000 cm-1 corresponding to C–C modes and C–H bending modes. Maximum hardness of the deposited films is found to be ~15 GPa. Band gap of the DLC films is ~3.5 eV. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) pictures show that the deposited films are amorphous. Deposition mechanism of wide band gap DLC film is explained on the basis of subplantation model.

scholarly journals h-BN-TiO2Nanocomposite for Photocatalytic Applications

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Václav Štengl ◽  
Jiří Henych ◽  
Michaela Slušná
Keyword(s):  
Diffuse Reflectance Spectroscopy ◽  
High Resolution Electron Microscopy ◽  
Bet Surface Area ◽  
Reactive Black 5 ◽  
Force Microscopy ◽  
Resolution Electron ◽  
Spin Resonance ◽  
Electric Force Microscopy ◽  
Photoinduced Charge ◽  
Hydrolysis Of

h-BN-TiO2nanocomposites were synthesized by the thermal hydrolysis of titanium peroxo-complexes in the presence of exfoliated h-BN. The bulk h-BN was prepared by annealing mixture of boric acid and urea, and high intensity ultrasound was used for its exfoliation. The prepared samples were characterized by X-ray powder diffraction (XRD), infrared spectroscopy, Raman spectroscopy, electron spin resonance (ESR), high resolution electron microscopy, BET surface area, and BJH porosity measurement. The UV-Vis diffuse reflectance spectroscopy was employed to estimate band-gap energies. The photoinduced charge on the surface of h-BN-TiO2nanocomposites was visualized using electric force microscopy (EFM). The photocatalytic activity was determined by azo dyes Orange II and Reactive Black 5 photobleaching. The highest rate constantk= 0.0762 min−1and 0.0164 min−1, under UV and visible light irradiation, respectively, showed sample denoted TiP050BN with moderate concentration of h-BN.

Sign in / Sign up

Export Citation Format

Share Document