Potential steps at C60-TiOPc-Ag(111) interfaces: ultrahigh-vacuum-noncontact scanning probe metrology.

Nanoscale structure-electric potential relations in films of the organic molecular semiconductors C(60) and titanyl phthalocyanine (TiOPc) on Ag(111) have been measured under UHV conditions. Noncontact force methods were utilized to image domain structures and boundaries with molecular resolution, while simultaneously quantifying the local surface electric potential. Sensitivity and spatial resolution for the local potential measurement were first established on Ag(111) through direct observation of the electrical dipole and potential step, φ(step) = 10 ± 3 mV, of monatomic crystallographic steps. A local surface potential increase of 27 ± 11 mV occurs upon crossing the boundary between the neat Ag(111) surface and C(60) islands. Potential steps in binary C(60)-TiOPc films, nanophase-separated into crystalline C(60) and TiOPc domains, were then mapped quantitatively. The 207 ± 66 mV potential step across the C(60)-to-TiOPc domain boundary exhibits a 3.6 nm width that reflects the spatial resolution for electric potential across a material interface. The absence of potential asymmetry across this lateral interface sets the upper bound for the C(60)-TiOPc interface dipole moment as 0.012 e nm.

The impact of digital transformation on the total factor productivity of heavily polluting enterprises.

In the digital economy, the relationship between digital transformation and a company's total factor productivity has profound implications for high-quality business development. Heavy polluters are given more environmental responsibility because of their high pollution and emission characteristics. This paper analyses the theoretical framework for the impact of digital transformation on the total factor productivity of heavily polluting firms. Using a sample of Shanghai and Shenzhen A-share heavy polluters from 2010 to 2020, we explore how the digital transformation of heavy polluters affects the total factor productivity of firms. The study found that the digital transformation of heavily polluting companies can effectively improve total factor productivity, internally by increasing their level of green technology innovation and externally by increasing their willingness and capacity for corporate social responsibility. At the same time, digital transformation can improve total factor productivity by reducing cost stickiness, revealing the "black box" in which digital transformation affects the total factor productivity of an enterprise. It was further found that the digital transformation of companies with high levels of environmental investment, large enterprises, those in non-manufacturing industries, and heavy polluters of a state-owned nature had a more significant impact on total factor productivity. The findings of the study provide empirical evidence for the digital transformation of heavily polluting companies to improve productivity and the green transformation of the economy for companies under the low carbon goal.

Polymorphism in self-assembled structures of 9-anthracene carboxylic acid on Ag(111).

Surface self-assembly process of 9-anthracene carboxylic acid (AnCA) on Ag(111) was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density.

Directed organization of C70 kagome lattice by titanyl phthalocyanine monolayer template.

Controlled deposition of titanyl phthalocyanine (TiOPc) on Ag(111) produces a honeycomb monolayer phase consisting of TiOPc molecules with two distinctive tilt angles. This periodic arrangement of polar molecules is used to direct C(70) growth into low-density 3D films with novel C(70) kagome lattice arrangements. Structural models for the C(70) kagome lattice are determined from layer-by-layer scanning tunneling microscopy images and related to the dipolar TiOPc template and C(70)'s anisotropic polarizability. Molecular templates with designed electrostatic features offer a practical method to control 3D film organization on the nanoscale by harnessing anisotropic molecular interactions at the growth interface.

The importance of bulk Ti3+ defects in the oxygen chemistry on titania surfaces.

The role of bulk defects in the oxygen chemistry on reduced rutile TiO(2)(110)-(1 × 1) has been studied by means of temperature-programmed desorption spectroscopy and scanning tunneling microscopy measurements. Following O(2) adsorption at 130 K, the amount of O(2) desorbing at ∼410 K initially increased with increasing density of surface oxygen vacancies but decreased after further reduction of the TiO(2)(110) crystal. We explain these results by withdrawal of excess charge (Ti(3+)) from the TiO(2)(110) lattice to oxygen species on the surface and by a reaction of Ti interstitials with O adatoms upon heating. Important consequences for the understanding of the O(2)-TiO(2) interaction are discussed.

TiOPc molecular dislocation networks as nanotemplates for C60 cluster arrays.

By controlled deposition, TiOPc, a molecular semiconductor with anisotropic interactions can generate a molecular film with a characteristic pattern repeat size of 15 nm. This structure then served as a nanotemplate for a superlattice of C(60) clusters with characteristic diameters of 7 nm. As a result, C(60) deposition on the TiOPc film template forms a pattern of nanophase-separated C(60) and TiOPc domains with a characteristic domain size of 7 nm. This feature size is matched to the exciton diffusion length in photovoltaic materials composed of small organic molecules. A dislocation network in a molecular film provides a promising method for generating pattern features on the several-nanometer length scale, bridging the practical limits of "bottom up" and "top down" strategies.

Unravelling Site-Specific Photo-Reactions of Ethanol on Rutile TiO2(110).

Finding the active sites of catalysts and photo-catalysts is crucial for an improved fundamental understanding and the development of efficient catalytic systems. Here we have studied the photo-activated dehydrogenation of ethanol on reduced and oxidized rutile TiO2(110) in ultrahigh vacuum conditions. Utilizing scanning tunnelling microscopy, various spectroscopic techniques and theoretical calculations we found that the photo-reaction proceeds most efficiently when the reactants are adsorbed on regular Ti surface sites, whereas species that are strongly adsorbed at surface defects such as O vacancies and step edges show little reaction under reducing conditions. We propose that regular Ti surface sites are the most active sites in photo-reactions on TiO2.

Ethanol Diffusion on Rutile TiO2(110) Mediated by H Adatoms.

We have studied the diffusion of ethanol on rutile TiO2(110)-(1 × 1) by high-resolution scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. Time-lapsed STM images recorded at ∼200 K revealed the diffusion of ethanol molecules both parallel and perpendicular to the rows of surface Ti atoms. The diffusion of ethanol molecules perpendicular to the rows of surface Ti atoms was found to be mediated by H adatoms in the rows of bridge-bonded O (Obr) atoms similarly to previous results obtained for water monomers. In contrast, the diffusion of H adatoms across the Ti rows, mediated by ethanol molecules, was observed only very rarely and exclusively on fully hydrogenated TiO2(110) surfaces. Possible reasons why the diffusion of H adatoms across the Ti rows mediated by ethanol molecules occurs less frequently than the cross-row diffusion of ethanol molecules mediated by H adatoms are discussed.