Nanoantenna-assisted plasmonic enhancement of IR absorption of vibrational modes of organic molecules

• Alexander G. Milekhin,
• Olga Cherkasova,
• Sergei A. Kuznetsov,
• Ilya A. Milekhin,
• Ekatherina E. Rodyakina,
• Alexander V. Latyshev,
• Sreetama Banerjee,
• Georgeta Salvan and
• Dietrich R. T. Zahn

Beilstein J. Nanotechnol. 2017, 8, 975–981, doi:10.3762/bjnano.8.99

• previously [23]. Note that the excitation energy was 1.96 eV (632.8 nm), which matches well with the HOMO–LUMO gap energy of CoPc (1.9 eV). The coincidence of the excitation energy with that of the electronic transitions in CoPc defines the conditions for resonant Raman scattering (RRS) in CoPc. In addition

Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals

• Ivan Shtepliuk,
• Jens Eriksson,
• Volodymyr Khranovskyy,
• Tihomir Iakimov,
• Anita Lloyd Spetz and
• Rositsa Yakimova

Beilstein J. Nanotechnol. 2016, 7, 1800–1814, doi:10.3762/bjnano.7.173

• effect manifests itself in a modification of the electron density distributions for HOMO and LUMO and, therefore, the HOMO–LUMO gap. In the case of pristine graphene, LUMO and HOMO are delocalized over the entire surface of the 3 × 3 graphene cluster. As can be seen from Figure 5, there is no hybridizing

• , such features of electron density distribution depending on the interaction of the C30H14 with heavy metals are correlated with the values of the HOMO–LUMO gap. The original HOMO–LUMO gap for a pristine graphene-like cluster estimated from the DFT calculations is approximately 2.230 eV. To our surprise

• , the interaction of graphene with cadmium and mercury atoms does not influence significantly the energy gap of the graphene cluster (a HOMO–LUMO value of 2.232 eV is refined in both cases). Meanwhile, a drastic change in molecular orbitals and HOMO–LUMO gap compared to the pristine graphene cluster has

Rigid multipodal platforms for metal surfaces

• Michal Valášek,
• Marcin Lindner and
• Marcel Mayor

Beilstein J. Nanotechnol. 2016, 7, 374–405, doi:10.3762/bjnano.7.34

• molecular orbital (HOMO). In conjugated systems this gap is smaller (about 3 eV) than the HOMO–LUMO gap of saturated molecules (about 7 eV) [17]. The conductance of a conjugated system depends on several factors, and not only the length of the conjugated system and its anchoring groups have a large

Core-level spectra and molecular deformation in adsorption: V-shaped pentacene on Al(001)

• Anu Baby,
• He Lin,
• Gian Paolo Brivio,
• Luca Floreano and
• Guido Fratesi

Beilstein J. Nanotechnol. 2015, 6, 2242–2251, doi:10.3762/bjnano.6.230

• reduction in the HOMO–LUMO gap of the free V-shaped molecule by 0.5 eV which decreases further for adsorption at the B site due to electron transfer. Upon adsorption, these states broaden and spread as a result of the substantial hybridization with the Al surface states. In particular for the LUMO an

• -shaped structural deformation alone reduces the HOMO–LUMO gap of the free molecule by 0.5 eV which facilitates the filling of LUMO by getting electronic charge from aluminum and is hence absent in the NEXAFS spectrum [15]. In pentacene, C1 has the highest weight on LUMO but instead a node for LUMO+1 as

The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors

• Rachel M. Thorman,
• Ragesh Kumar T. P.,
• D. Howard Fairbrother and
• Oddur Ingólfsson

Beilstein J. Nanotechnol. 2015, 6, 1904–1926, doi:10.3762/bjnano.6.194

• predominantly through a higher energy resonance, which the authors assigned as a core-excited resonance (two-particle-one-hole resonance) associated with a HOMO–LUMO transition. The fragment formation through this resonance peaks close to 4.5 eV. From thermochemical considerations it is clear that multiple

Enhanced fullerene–Au(111) coupling in (2√3 × 2√3)R30° superstructures with intermolecular interactions

• Michael Paßens,
• Rainer Waser and
• Silvia Karthäuser

Beilstein J. Nanotechnol. 2015, 6, 1421–1431, doi:10.3762/bjnano.6.147

• accordance with the increased brightness of the en-bright C60, that is, the difference in apparent height with respect to the bright 6:6-top C60, as shown in Figure 4b. The HOMO–LUMO gap is almost unaffected by the given superstructure environment and remains at 2.7 eV, as well as the FWHM of the LUMO does

• the en-bright C60 with a nearby Au adatom, as discussed above for the u-R30° domain (Figure 5). In the case of the adsorption of a single C60 in an adatom geometry, DFT based calculations [43] indicate also a splitting of the LUMO orbitals and a shift to lower energies while the HOMO–LUMO gap is not

Electron and heat transport in porphyrin-based single-molecule transistors with electro-burnt graphene electrodes

• Hatef Sadeghi,
• Sara Sangtarash and
• Colin J. Lambert

Beilstein J. Nanotechnol. 2015, 6, 1413–1420, doi:10.3762/bjnano.6.146

• the ground state energy (see Computational Methods). We carried out a spin-polarized calculation since the d orbitals of the Zn atom could be filled to different degrees. It is well-known that Kohn–Sham DFT eigenvalues usually underestimate the HOMO–LUMO gap and DFT typically does not predict their

• yields Eg = 3.84 eV. The Kohn–Sham DFT eigenvalues predict and using the generalised gradient approximation/Perdew–Burke–Ernzerhof exchange-correlation functional (GGA/PBE), which results in a Kohn–Sham DFT gap of for the gas phase molecule. Figure 2 shows the iso-surfaces of the HOMO−1, HOMO, LUMO and

• on the electron transport since they have high orbital energies far from the HOMO–LUMO resonances. Although the current mostly passes through the edge of the ribbon, it does not have much effect on the transport due to the weak coupling between the anchor and electrode surfaces. We used the tight

Can molecular projected density of states (PDOS) be systematically used in electronic conductance analysis?

• Tonatiuh Rangel,
• Gian-Marco Rignanese and
• Valerio Olevano

Beilstein J. Nanotechnol. 2015, 6, 1247–1259, doi:10.3762/bjnano.6.128

• catholique de Louvain (CISM/UCL), by the Consortium des Équipements de Calcul Intensif en Fédération Wallonie Bruxelles (CÉCI), and by the French GENCI supercomputing center (Project i2012096-655). Electronic density isosurfaces (red) of the HOMO−1, HOMO, LUMO and LUMO+1 molecular orbitals of BDA as obtained

• molecular PDOS is the sum of the PDOS onto the MOs from HOMO−2 to LUMO+2 as obtained from Method 2. Electronic density isosurfaces (red) of the HOMO−1, HOMO, LUMO and LUMO+1 molecular orbitals of BDT as obtained with the two traditional methods as well as with the new method (see text). For Method 1, the

Charge carrier mobility and electronic properties of Al(Op)₃: impact of excimer formation

• Andrea Magri,
• Pascal Friederich,
• Bernhard Schäfer,
• Valeria Fattori,
• Xiangnan Sun,
• Timo Strunk,
• Velimir Meded,
• Luis E. Hueso,
• Wolfgang Wenzel and
• Mario Ruben

Beilstein J. Nanotechnol. 2015, 6, 1107–1115, doi:10.3762/bjnano.6.112

• . Keywords: charge carrier mobility; HOMO–LUMO energy levels; photophysical characterization; TFT devices; tris-(1-oxo-1H-phenalen-9-olate)aluminum(III); Introduction Since the field of organic electronics has emerged, interest in organic semiconductors (OSCs) has substantially increased [1]. The efficiency

• ligand on potential OSC opto-electronic performance. Intrigued by establishing a direct relation between the chemical structure and the electronic properties of OSCs, we have fully characterized Al(Op)3 by means of electrochemical and photophysical techniques in solution to estimate the HOMO/LUMO values

• evaluate the potential incorporation of Al(Op)3 in organic-based devices, we have estimated its HOMO/LUMO energies by electrochemical and photophysical methods in solution. The electron affinity (EA) was measured by means of cyclic voltammetry and the ionization potential (IP) was determined by the

Spectroscopic mapping and selective electronic tuning of molecular orbitals in phosphorescent organometallic complexes – a new strategy for OLED materials

• Pascal R. Ewen,
• Jan Sanning,
• Tobias Koch,
• Nikos L. Doltsinis,
• Cristian A. Strassert and
• Daniel Wegner

Beilstein J. Nanotechnol. 2014, 5, 2248–2258, doi:10.3762/bjnano.5.234

• strategy of fine-tuning both levels independently, which should permit the tunability of the HOMO–LUMO gap (and thus the emission color) as well as charge-injection barriers in a device. Results and Discussion Methods and sample preparation The experiments were performed under ultrahigh vacuum conditions

• measuring dI/dV maps within the HOMO–LUMO gap where no resonant tunneling into MO occurs [41]. Therefore, the HOMO–1 is observed twice, below and above EF. This situation is again schematically depicted in Figure 3b, where two red-colored broadened peaks represent the observed MOs at the Pt site. The fact

• charge-injection barriers and the HOMO–LUMO gap, and hence the emission color, independently. We will perform further investigations on this matter to test the validity of this concept. Conclusion We showed that various phosphorescent Pt(II) complexes can be deposited reliably and without dissociation

Numerical investigation of the effect of substrate surface roughness on the performance of zigzag graphene nanoribbon field effect transistors symmetrically doped with BN

• Majid Sanaeepur,
• Arash Yazdanpanah Goharrizi and
• Mohammad Javad Sharifi

Beilstein J. Nanotechnol. 2014, 5, 1569–1574, doi:10.3762/bjnano.5.168

• increased number of conducting channels while the observed increase in the off-current is due to decreased HOMO–LUMO gap (and, consequently, a decreased transport gap). As a result of this, the on/off-current ratio decreases from 1.6 × 106 in the 3h-2BN device to 156 in the 5h-2BN device (see inset of

DFT study of binding and electron transfer from colorless aromatic pollutants to a TiO₂ nanocluster: Application to photocatalytic degradation under visible light irradiation

• Corneliu I. Oprea,
• Petre Panait and
• Mihai A. Gîrţu

Beilstein J. Nanotechnol. 2014, 5, 1016–1030, doi:10.3762/bjnano.5.115

• Ph has a HOMO→LUMO transition at 248 nm, a HOMO→LUMO+1 transition at 215 nm and HOMO−1→LUMO transitions at 187 nm. In the case of BA the transitions are at 259 nm (HOMO→LUMO), 237 nm (HOMO−1→LUMO), and 192 nm (HOMO→LUMO+1). Similarly, for pHBA we found transitions at 258 nm (HOMO→LUMO), 217 nm (HOMO

• →LUMO+1), and 191 nm (HOMO−1→LUMO+1). Finally, in the case of SA the spectrum is closest to the visible range: 289 nm (HOMO→LUMO), 234 nm (HOMO−1→LUMO), and 207 nm (HOMO→LUMO+1). All transitions have π–π* character, for all pollutants. The HOMO→LUMO transitions are weak, the most intense peaks being

• ) bands correspond for all systems to HOMO→LUMO transitions. However, these transitions have very small oscillator strengths, as it can be seen in Table 4. For instance, the only adsorbed pollutant with a band beyond the blue region of the spectrum is Ph, whose first transition is at 524 nm, but the

CoPc and CoPcF₁₆ on gold: Site-specific charge-transfer processes

• Fotini Petraki,
• Heiko Peisert,
• Johannes Uihlein,
• Umut Aygül and
• Thomas Chassé

Beilstein J. Nanotechnol. 2014, 5, 524–531, doi:10.3762/bjnano.5.61

• the monolayer coverage there is a tendency of the work function toward higher values, reaching a plateau at about 5.50 ± 0.1 eV. Recently calculated energy level diagrams predict molecular HOMO (LUMO) energies of about −5.3 eV (−3.1 eV) and −6.7 eV (−4.5 eV) for CoPc and CoPcF16, respectively [35

Optimization of solution-processed oligothiophene:fullerene based organic solar cells by using solvent additives

• Gisela L. Schulz,
• Marta Urdanpilleta,
• Roland Fitzner,
• Eduard Brier,
• Elena Mena-Osteritz,
• Egon Reinold and
• Peter Bäuerle

Beilstein J. Nanotechnol. 2013, 4, 680–689, doi:10.3762/bjnano.4.77

• in CH2Cl2/TBAPF6 solutions (HOMO/LUMO vs Fc/Fc+vac = −5.1 eV). Photovoltaic parameters of solar cells fabricated using DCV5T-Bu4:PCBM from chlorobenzene, chloronaphthalene as additive, and spin-coated at 80 °C. Device structure: ITO|PEDOT:PSS|DCV5T-Bu4:PCBM (1:1)|LiF|Al. Comparing vacuum [21] and

Structural and electronic properties of oligo- and polythiophenes modified by substituents

• Simon P. Rittmeyer and
• Axel Groß

Beilstein J. Nanotechnol. 2012, 3, 909–919, doi:10.3762/bjnano.3.101

• cell. In order to preserve the electric neutrality of the cell, a compensating background charge is generated by default. As we are interested in the HOMO–LUMO gap of oligothiophenes and the band gaps of polythiophenes, we have to be concerned with the well-known deficiency of DFT using current-day GGA

• effort in plane-wave codes such as VASP. As we are mainly interested in trends in the local density of states depending on the choice of the substituent, GGA-DFT calculations should be sufficient to reproduce these trends. However, one has to be aware that all absolute values of HOMO–LUMO and band gaps

• systems [38], but there is definitely a flattening effect of a growing chain length as the trimer (2,5-bis(thiophen-2-yl)thiophene, TTp) was predicted to show a totally flat structure. This should be due to the extended π-system and, hence, definitely agrees with expectations. Regarding HOMO–LUMO gaps for

Current–voltage characteristics of single-molecule diarylethene junctions measured with adjustable gold electrodes in solution

• Bernd M. Briechle,
• Youngsang Kim,
• Philipp Ehrenreich,
• Artur Erbe,
• Dmytro Sysoiev,
• Thomas Huhn,
• Ulrich Groth and
• Elke Scheer

Beilstein J. Nanotechnol. 2012, 3, 798–808, doi:10.3762/bjnano.3.89

• to 0.62 eV for the symmetric I–V’s and 0.69 eV for asymmetric ones. It is slightly smaller than in the open state, where we find E0 = 0.67 eV for symmetric and 0.75 eV for asymmetric I–V’s, in agreement with the simple expectation that the closed state should have a smaller HOMO–LUMO gap and if no

Transmission eigenvalue distributions in highly conductive molecular junctions

• Justin P. Bergfield,
• Joshua D. Barr and
• Charles A. Stafford

Beilstein J. Nanotechnol. 2012, 3, 40–51, doi:10.3762/bjnano.3.5

• in the top panel of Figure 1, we see that screening due to the nearby Pt tips reduces the HOMO–LUMO gap by 33% on average, from 10.39 eV in the gas-phase to 6.86 eV over the junction ensemble. The screening of intramolecular Coulomb interactions by nearby conductor(s) illustrated in Figure 1 leads to

• accuracy of the approximate method shown in Figure 7. Similarly, in the vicinity of the LUMO resonance, the isolated LUMO resonance approximation accurately characterizes the average transmission. The HOMO–LUMO asymmetry in the average transmission function arises because the HOMO resonance couples more

When “small” terms matter: Coupled interference features in the transport properties of cross-conjugated molecules

• Gemma C. Solomon,
• Justin P. Bergfield,
• Charles A. Stafford and
• Mark A. Ratner

Beilstein J. Nanotechnol. 2011, 2, 862–871, doi:10.3762/bjnano.2.95

• features to lie. Simple predictive schemes [46][47] based on single-particle models have been developed to provide a quick answer as to whether a particular topology will result in interference features in the HOMO–LUMO gap, but “the devil is in the details”. In many molecules the HOMO–LUMO gap is on the

An MCBJ case study: The influence of π-conjugation on the single-molecule conductance at a solid/liquid interface

• Wenjing Hong,
• Hennie Valkenier,
• Gábor Mészáros,
• David Zsolt Manrique,
• Artem Mishchenko,
• Alexander Putz,
• Pavel Moreno García,
• Colin J. Lambert,
• Jan C. Hummelen and
• Thomas Wandlowski

Beilstein J. Nanotechnol. 2011, 2, 699–713, doi:10.3762/bjnano.2.76

• as the position of the EHOMO level. This result is in good agreement with AM1-RHF calculations, performed with Hyperchem Release 7.52, and the level alignment, based on UPS data, of a related AQ-type molecular wire, EHOMO(Hyperchemcorr) = −5.74 eV [14]. The HOMO–LUMO gap is estimated at 2.90 eV from

Terthiophene on Au(111): A scanning tunneling microscopy and spectroscopy study

• Berndt Koslowski,
• Anna Tschetschetkin,
• Norbert Maurer,
• Elena Mena-Osteritz,
• Peter Bäuerle and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 561–568, doi:10.3762/bjnano.2.60

• -separation (I-V) and constant-current (z-V) STS clearly reveal the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbitals, which are found at −1.2 eV and +2.3 eV, respectively. The HOMO–LUMO gap corresponds to that of a free molecule, indicating a rather weak interaction between 3T and Au

• within its HOMO–LUMO gap. A more quantitative analysis of this detail resolves a previous discrepancy between the fairly small apparent STM height of 3T molecules (1.4–2.0 nm, depending on tunneling bias) and a corresponding larger value of 3.5 nm based on X-ray standing wave analysis. An additionally

• asymmetric while the LUMO appears symmetric relative to the same axis. Thus, the HOMO allows identification of the orientation of the 3T molecules. Comparison to a ball-and-stick model of the 3T molecule, as inserted in Figure 4(a), and to the HOMO–LUMO distributions of a free 3T as calculated by Gaussian03

Septipyridines as conformationally controlled substitutes for inaccessible bis(terpyridine)-derived oligopyridines in two-dimensional self-assembly

• Daniel Caterbow,
• Daniela Künzel,
• Michael G. Mavros,
• Axel Groß,
• Katharina Landfester and
• Ulrich Ziener

Beilstein J. Nanotechnol. 2011, 2, 405–415, doi:10.3762/bjnano.2.46

• '-PhSpPy (15). The LUMO levels are at −9.46 kJ mol−1 and −8.59 kJ mol−1 for 3,3'-BTP (3) and 3,3'-PhSpPy (15), respectively. Still, it has to be noted that the accuracy of density functional theory for unoccupied states and HOMO–LUMO gaps is rather limited. Even though there are slight differences in the