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Non-destructive reference-free grazing incidence X-ray fluorescence (RF-GIXRF) is proposed as a highly effective analytical technique for extracting molecular arrangement density in self-assembled monolayers. The establishment of surface density standards through RF-GIXRF impacts various applications, from calibrating laboratory XRF setups to expanding its applicability in materials science, particularly in surface coating scenarios with molecular assemblies. Accurate determination of coverage density is crucial for proper functionalization and interaction, such as in assessing the surface concentration of probes on plasmonic nanostructures. However, limited synchrotron radiation access hinders widespread use, prompting the need for molecular surface density standards, especially for benchmarking substrates for surface-enhanced Raman and infrared absorption spectroscopies (SERS and SEIRA) as well as associated surface-enhanced techniques. Using reproducible densities on gold ensures a solid evaluation of the number of molecules contributing to enhanced signals, facilitating comparability across substrates. The research discusses the importance of employing molecular surface density standards for advancing the field of surface-enhanced spectroscopies, encouraging collaborative efforts in protocol development and benchmarking in surface science.

Abstract Nanoparticles are often measured using atomic force microscopy or other scanning probe microscopy methods. For isolated nanoparticles on flat substrates, this is a relatively easy task. However, in real situations, we often need to analyze nanoparticles on rough substrates or nanoparticles that are not isolated. In this article, we present a simple model for realistic simulations of nanoparticle deposition and we employ this model for modeling nanoparticles on rough substrates. Different modeling conditions (coverage, relaxation after deposition) and convolution with different tip shapes are used to obtain a wide spectrum of virtual AFM nanoparticle images similar to those known from practice. Statistical parameters of nanoparticles are then analyzed using different data processing algorithms in order to show their systematic errors and to estimate uncertainties for atomic force microscopy analysis of nanoparticles under non-ideal conditions. It is shown that the elimination of user influence on the data processing algorithm is a key step for obtaining accurate results while analyzing nanoparticles measured in non-ideal conditions.

The optical characterization of non-absorbing, homogeneous, isotropic polymer-like thin films with correlated, differently rough boundaries is essential in optimizing their performance in various applications. A central aim of this study is to derive the general formulae necessary for the characterization of such films. The applicability of this theory is illustrated through the characterization of a polymer-like thin film deposited by plasma-enhanced chemical vapor deposition onto a silicon substrate with a randomly rough surface, focusing on the analysis of its rough boundaries over a wide range of spatial frequencies. The method is based on processing experimental data obtained using variable-angle spectroscopic ellipsometry and spectroscopic reflectometry. The transition layer is considered at the lower boundary of the polymer-like thin film. The spectral dependencies of the optical constants of the polymer-like thin film and the transition layer are determined using the Campi–Coriasso dispersion model. The reflectance data are processed using a combination of Rayleigh–Rice theory and scalar diffraction theory in the near-infrared and visible spectral ranges, while scalar diffraction theory is used for the processing of reflectance data within the ultraviolet range. Rayleigh–Rice theory alone is sufficient for the processing of the ellipsometric data across the entire spectral range. We accurately determine the thicknesses of the polymer-like thin film and the transition layer, as well as the roughness parameters of both boundaries, with the root mean square (rms) values cross-validated using atomic force microscopy. Notably, the rms values derived from optical measurements and atomic force microscopy show excellent agreement. These findings confirm the reliability of the optical method for the detailed characterization of thin films with differently rough boundaries, supporting the applicability of the proposed method in high-precision film analysis. [ABSTRACT FROM AUTHOR]

A methodology based on molecular dynamics simulations is presented to determine the chemical potential of thiol self-assembled monolayers on a gold surface. The thiol de-solvation and then the monolayer formation are described by thermodynamic integration with a gradual decoupling of one molecule from the environment, with the necessary corrections to account for standard state changes. The procedure is applied both to physisorbed undissociated thiol molecules and to chemisorbed dissociated thiyl radicals, considering in the latter case the possible chemical potential of the produced hydrogen. We considered monolayers formed by either 7-mercapto-4-methylcoumarin (MMC) or 3-mercapto-propanoic acid (MPA) on a flat gold surface: the free energy profiles with respect to the monolayer density are consistent with a transition from a very stable lying-down phase at low densities to a standing-up phase at higher densities, as expected. The maximum densities of thermodynamically stable monolayers are compared to experimental measures performed with reference-free grazing-incidence X-ray fluorescence (RF-GIXRF) on the same systems, finding a better agreement in the case of chemisorbed thiyl radicals. [ABSTRACT FROM AUTHOR]

Copper oxide nanowires (NWs) are promising elements for the realization of a wide range of devices for low-power electronics, gas sensors, and energy storage applications, due to their high aspect ratio, low environmental impact, and cost-effective manufacturing. Here, we report on the electrical and thermal properties of copper oxide NWs synthetized through thermal growth directly on copper foil. Structural characterization revealed that the growth process resulted in the formation of vertically aligned NWs on the Cu growth substrate, while the investigation of chemical composition revealed that the NWs were composed of CuO rather than Cu2O. The electrical characterization of single-NW-based devices, in which single NWs were contacted by Cu electrodes, revealed that the NWs were characterized by a conductivity of 7.6 × 10−2 S∙cm−1. The effect of the metal–insulator interface at the NW–electrode contact was analyzed by comparing characterizations in two-terminal and four-terminal configurations. The effective thermal conductivity of single CuO NWs placed on a substrate was measured using Scanning Thermal Microscopy (SThM), providing a value of 2.6 W∙m−1∙K−1, and using a simple Finite Difference model, an estimate for the thermal conductivity of the nanowire itself was obtained as 3.1 W∙m−1∙K−1. By shedding new light on the electrical and thermal properties of single CuO NWs, these results can be exploited for the rational design of a wide range of optoelectronic devices based on NWs. [ABSTRACT FROM AUTHOR]