Micro-/macroscopic and density functional studies of the interactions between molybdenum trioxide and C60 molecule.

We have investigated the interactions between C60 and (MoO3)n using scanning tunneling microscopy with spectroscopy (STM/STS) and ex situ ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy in combination with density functional theory (DFT) calculations. The formation of (MoO3)n chemically bound to C60 is energetically favorable due to ΔG < 0 for n = 1, 2, 4, 6, 8, and 9, and they well reproduced the histogram of the height of (MoO3)n on the C60 (111) terrace obtained by a STM height-profile. STS results demonstrated the upward energy shift of both highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of C60 in the vicinity of (MoO3)n (n = 6 or 9), which is consistent with the previous results of the co-deposited C60/MoO3 film obtained using photoemission and inverse photoemission spectroscopy [Wang and Gao, Appl. Phys. Lett. 105, 111601 (2014), Yang et al., J. Phys.: Condens. Matter 28, 185502 (2016), and Li et al., J. Phys. Chem. C 118, 4869 (2014)]. Theoretical calculations of (MoO3)n (n = 1, 2, 4, 6, 8, and 9) chemically bound to C60 indicated that 0.01-0.32 holes are injected into C60 by (MoO3)n nanoclusters, and UV-vis-NIR and DFT results found that the hole doping to C60 is caused via the electron transfer from the HOMO of C60 to the LUMO of (MoO3)n. Furthermore, it is noted that the C60-(MoO3)n interactions exhibit a high heat resistance up to 250 °C by examining the UV-vis-NIR spectra of a co-deposited C60/MoO3 (6:4) film before and after thermal annealing. The present findings provide useful information for the practical use of P-type C60-based thermoelectric devices.

Morphological and optical properties of α- and ß-phase zinc (∥) phthalocyanine thin films for application to organic photovoltaic cells.

We have investigated the morphological and optical properties of α- and ß-phase Zinc Phthalocyanine (ZnPc) thin films for application to organic photovoltaic cells (OPVs). It was found that the α-phase is completely converted to the ß-phase by thermal annealing at 220 °C under ultrahigh vacuum conditions. When the α- to ß-phase transition takes place, the surface roughness of the ZnPc film became flat uniformly with a nanometer order of unevenness by anisotropic growth of crystalline grains along a lateral direction to substrates. Correspondingly, the optical absorbance of the ß-phase film became greater by 1.5-2 times than that of the α-phase one in an ultraviolet-visible-near infrared (UV-vis-NIR) wavelength range, which plays a role in increasing the number of photogenerated excitons. On the contrary, time-resolved photoluminescence measurements showed that the average lifetime of excitons for the ß-phase film became shorter by 1/6-1/7 than that for the α-phase one, which plays a role in decreasing the number of excitons achieving the donor/acceptor interface where excitons are separated to carriers (holes and electrons). Both the increase in the number and the shortening in the average lifetime have a trade-off relationship with each other for contribution to the photoelectric conversion efficiency of OPVs. Then, we examined an external quantum efficiency (EQE) of OPVs using the α- and ß-phase films as a donor and obtained that the former OPV (α-phase) exhibits a higher EQE by ∼2 times than the latter one (ß-phase) in the wavelength range of 400 nm-800 nm.

Spectroscopic and theoretical studies on the structural, electronic, and optical properties of zinc octaethylporphyrin/C60 co-deposited films.

We have examined the structural, electronic, and optical properties of zinc-octaethylporphyrin [Zn(OEP)]/C60 co-deposited films to elucidate the donor (D)-acceptor (A) interactions at the D/A interface of heterojunction organic solar cells (OSCs), using Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, and photoluminescence (PL) spectroscopy in combination with first-principles and semi-empirical calculations. The FT-IR and XRD results indicated that Zn(OEP) and C60 were mixed with each other at the molecular level in the co-deposited film. The theoretical calculations suggested that in the interfacial region, it is energetically preferable for the C60 molecule to face the center of the planar structure of Zn(OEP) at a distance of 2.8 Å rather than the edge of the structure at a distance of 5.0 Å. After consideration of the C60 solvent effects, this coordination model for C60-Zn(OEP) adequately explained the line shift of the UV-vis peaks with respect to the proportion of C60 in the co-deposited films. A comparison of the energy level diagrams of Zn(OEP) before and after the interaction with C60 revealed that the LUMO, HOMO, and HOMO-1 were significantly affected by the interaction with C60. In particular, the HOMO-1 wave function became spread over a portion of C60, although the charge transfer between Zn(OEP) and C60 was almost negligible. Since no PL peaks (S1 → S0) from the excited Soret band of Zn(OEP) were observed for the Zn(OEP)/C60 co-deposited films, the D/A mixing layers played a crucial role in completely dissolving the photogenerated excitons to electrons-hole pairs that cause the short-circuit current, which is relevant to improving the energy conversion efficiency of OSCs.

The uptake characteristics of Prussian-blue nanoparticles for rare metal ions for recycling of precious metals from nuclear and electronic wastes.

We have examined the uptake mechanisms of platinum-group-metals (PGMs) and molybdenum (Mo) ions into Prussian blue nanoparticles (PBNPs) in a nitric acid solution for 24-h sorption test, using inductively coupled plasma atomic emission spectroscopy, powder XRD, and UV-Vis-NIR spectroscopy in combination with first-principles calculations, and revealed that the Ru4+ and Pd2+ ions are incorporated into PBNPs by substitution with Fe3+ and Fe2+ ions of the PB framework, respectively, whereas the Rh3+ ion is incorporated into PBNPs by substitution mainly with Fe3+ and minorly with Fe2+ ion, and Mo6+ ion is incorporated into PBNPs by substitution with both Fe2+ and Fe3+ ions, with maintaining the crystal structure before and after the sorption test. Assuming that the amount of Fe elusion is equal to that of PGMs/Mo substitution, the substitution efficiency is estimated to be 39.0% for Ru, 47.8% for Rh, 87% for Pd, and 17.1% for Mo6+. This implies that 0.13 g of Ru, 0.16 g of Rh, 0.30 g of Pd, and 0.107 g of Mo can be recovered by using 1 g PBNPs with a chemical form of KFe(III)[Fe(II)(CN)6].

[H(x)TeV9O28]((5-x)-) (x=1 and 2): vanadotellurates with decavanadate structure.

Two new vanadotellurates, [HTeV(9)O(28)](4-) and [H(2)TeV(9)O(28)](3-) have been synthesized and structurally characterized as tetra-n-butylammonium (TBA) salts: TBA(4)[HTeV(9)O(28)]·2CH(3)CN [triclinic, space group P ̅1, a = 16.7102(6) Å, b = 17.4680(7) Å, c = 17.9634(7) Å, α = 74.412(1)°, ß = 67.494(1)°, γ = 74.160(2)°, Z = 2] and TBA(3)[H(2)TeV(9)O(28)] [monoclinic, space group P2(1)/c, a = 13.0013(5) Å, b = 19.157(1) Å, c = 28.453(1) Å, ß = 97.222(2)°, Z = 4]. The results of the structural analyses indicate that the four O atoms that bridge two V atoms on the Te side are the most basic ones in the structure. The results of density-functional theory (DFT) calculations support this view.

Resolving Site-Specific Energy Levels of Small-Molecule Donor-Acceptor Heterostructures Close to Metal Contacts.

The active material of optoelectronic devices must accommodate for contacts which serve to collect or inject the charge carriers. It is the purpose of this work to find out to which extent properties of organic optoelectronic layers change close to metal contacts compared to known properties of bulk materials. Bottom-up fabrication capabilities of model interfaces under ultrahigh vacuum and single-atom low temperature (LT)-STM spectroscopy with density functional theory (DFT) calculations are used to detect the spatial modifications of electronic states such as frontier-orbitals at interfaces. The system under consideration is made of a silver substrate covered with a blend of C60 and ZnPc molecules of a few monolayers. When C60 and ZnPc are separately adsorbed on Ag(111), they show distinct spectroscopic features in STM. However, when C60 is added to the ZnPc monolayer, it shows scanning tunneling spectra similar to ZnPc, revealing a strong interaction of C60 with the ZnPc induced by the substrate. DFT calculations on a model complex confirm the strong hybridization of C60 with ZnPc layer upon adsorption on Ag(111), thus highlighting the role of boundary layers where the donor-acceptor character is strongly perturbed. The calculation also reveals a significant charge transfer from the Ag to the complex that is likely responsible for a downward shift of the molecular LUMO in agreement with the experiment.

The uptake mechanism of palladium ions into Prussian-blue nanoparticles in a nitric acid solution toward application for the recycling of precious metals from electronic and nuclear wastes.

We have investigated the uptake mechanism of palladium (Pd: one of the most important elements in industry used as a catalyst) ions into Prussian-blue nanoparticles (PBNPs) in a nitric acid solution via high-resolution electron transmission microscopy, inductively coupled plasma atomic emission spectroscopy, powder X-ray diffraction, and ultraviolet-visible-near infrared spectroscopy in combination with first principles calculations. Comparison of the structural and electronic properties of PBNPs between before and after a 24 h sorption test reveals that the Pd2+ ions incorporated into PBNPs by the substitution of Fe2+ ions of the PB framework while maintaining the crystal structure, and the substitution efficiency is estimated to be 87% per PB unit cell. This implies that 0.30 g of Pd can be recovered by using 1 g of PB having the chemical formula KFe(iii)[Fe(ii)(CN)6]. The present finding suggests that PB (or its analogues) can be applied to recycle noble and rare metals from electronic and nuclear wastes.

Bilateral Internal Carotid and Left Vertebral Artery Dissection after Blunt Trauma: A Case Report and Literature Review.

Multi-vessel cervical arterial injury after blunt trauma is rare, and its pathophysiology is unclear. Although blunt cerebrovascular injury is a common cause of cerebral ischemia, its management is still controversial. We describe a 23-year-old man in previously good health who developed three-vessel cervical arterial dissections due to blunt trauma. He was admitted to our emergency and critical care center after a motor vehicle crash. Computed tomography showed a thin, acute subdural hematoma in the right hemisphere and fractures of the odontoid process (Anderson type III), pelvis, and extremities. He was treated conservatively, and about 1 month later, he developed bleariness. Computed tomography angiography showed bilateral internal carotid and left vertebral artery dissection. Aspirin therapy was started immediately, and then clopidogrel was added to the regimen. Two weeks later, magnetic resonance angiography (MRA) showed improved blood flow of the vessels. Only aspirin therapy was continued. About 3 months after discharge, MRA demonstrated further improvement of the blood flow of both internal carotid arteries, but the dissection flap on the right side remained. Therefore, we extended the duration of antiplatelet therapy. On the basis of our experience with this case, we think that antithrombotic therapy is crucial for the management of multi-vessel cervical arterial injury, and agents should be used properly according to the injury grade and phase; however, further study is needed to confirm this recommendation.