Thin Films and Bulk Phases Conucleate at the Interfaces of Pentacene Thin Films

Abstract

Pentacene deposited on silica adopts two different packing arrangements. The kinetically favorable thin-film phase (TFP) occurs at lower substrate temperatures and thinner deposition thicknesses relative to the thermodynamically stable bulk phase (BP). Both phases orient in a tilted edge-on motif, where the BP is tilted further from the perpendicular, identifiable using X-ray diffraction (XRD) techniques. Different types of growth on SiO 2 have been proposed. One is that deposition at the interface begins with the TFP, independent of substrate temperature, while the BP deposits over it after a temperature-dependent critical deposition thickness is reached. Others have found both phases to begin their temperaturedependent growth at the interface. Using an interfacial spectroscopic technique, vibrational sum frequency generation, paired with Fourier transform infrared spectroscopy and XRD, we determine that conucleation of both phases at the interface takes place during pentacene thin-film growth.

Insight into the Adsorption Structure of TIPS-Pentacene on Noble Metal Surfaces

“…Most literature studies on these materials focus on acenes, such as pentacene and their derivatives, ,,,, rubrene, − and perylene diimides. − Most of these studies are either in the solution phase or in single/polycrystalline phases and investigate elementary charge transfer and electronic processes of these materials, − assisted by related computational studies. , In application, however, these chromophores are often in single or polycrystalline thin films, ,− and characterization of their properties at interfaces and within thin films becomes essential. For instance, substrate choice and temperature can be used as a control for the pentacene phase and orientation in a film . Therefore, the adsorption of molecules on solid surfaces can alter the chemistry of these organic molecules, especially on metal surfaces, underscoring the significance of understanding the strength of the adsorbate–substrate interactions (along with lateral adsorbate–adsorbate interactions) for determining molecular orientation, structure and growth and how the adsorption geometry defines the electronic structure of the adsorbate–substrate system.…”

Water Capture Mechanisms at Zeolitic Imidazolate Framework Interfaces

“…Here, by selectively probing the water clustering step, using a spatially resolved vibrational sum-frequency generation (VSFG) spectroscopy and MD simulations with the MB-pol − water model, we study the water uptake mechanism of ZIF-90, a hydrophilic MOF that can adsorb water at low RH without open metal sites and be modified postsynthetically. , We find that ZIF-90 adsorbs water by mechanism 1. This study emphasizes the importance of interface-specific techniques, − determining that the competition between water–water and water–framework interactions dictates the uptake mechanism. Understanding ZIF-90 water uptake mechanism lays the foundation to further optimize its and other MOF’s water harvesting function through post synthesis.…”

“…This work is feasible by selectively probing the water clustering step, using a spatially-resolved vibrational sum-frequency generation (VSFG) spectroscopy and MB-pol [18][19][20] water-based simulations. 11 This study emphasizes the importance of interfacial-specific techniques [21][22][23][24][25][26] to decipher the effects of water-water and water-framework interactions on the water adsorption mechanism, which can provide guidance to the rational design of MOFs for water harvesting. Two crucial technical aspects that enable the micronresolved VSFG to probe adsorbed water at interior MOF surfaces.…”

Water Capture Mechanisms at Zeolitic Imidazolate Framework Interfaces

“…26,27 We find that ZIF-90 adsorbs water by mechanism 1. This study emphasizes the importance of interfacial-specific techniques, [28][29][30][31][32][33] determining that the competition between water-water and waterframework interactions dictates the uptake mechanism. Understanding ZIF-90 water uptake mechanism lays the foundation to further optimize its and other MOF's water harvesting function through post synthesis.…”