Silver Tarnishing Mechanism Revealed by Molecular Dynamics Simulations

The Degradation of Daguerreotypes and the Relationship with Their Multi-Material Structure: A Multimodal Investigation

Preserving and analytically examining daguerreotypes is particularly challenging because of their multi-material and multi-component structure. Various sensors have been exploited to examine mainly the image plates of the daguerreotypes even though the degradation goes beyond this component. Micro-analyses have been the preferred method due to the nanoscale structure of the image particles. In this work, we propose comprehensive multi-modal non-invasive sensing to investigate the corrosion products present in nine daguerreotypes from the Fondazione Alinari per la Fotografia (FAF, Florence, Italy). The methodology proposed includes chemical and morphological analyses: portable X-ray fluorescence spectrometry (pXRF), Raman microspectroscopy (μ-Raman), and micro-Fourier transform infrared spectroscopy in reflection mode (μ-rFTIR) for the chemical identification. For the first time, optical coherence tomography (OCT) was deployed to record the cross-sectional and morphological data of the relevant corrosion formations on daguerreotypes in a contactless way. The results allowed the characterization, in a non-invasive mode at a microscopic level, of a wide range of degradation products produced by the interaction of the different elements present in the structure of the daguerreotypes. The aim was to verify the performance of the proposed methodology and to link the chemical and physical complexity of the entire structure, disclosed by the state-of-art sensors, to the daguerreotype degradation. The results draw attention to the need to monitor not only the image condition but the whole object as a partially closed system in constant interaction internally and with the environment.

Tailoring Silver Nanowire Nanocomposite Interfaces to Achieve Superior Stretchability, Durability, and Stability in Transparent Conductors

Silver nanowires (AgNWs) have been considered as a promising candidate for transparent stretchable conductors (TSCs). However, the strong interface mismatch of stiff AgNWs and elastic substrates leads to the stress concentration at their interface and ultimately the low stretchability and poor durability of TSCs. Here, to address the interfacial mismatch of AgNWs-based TSCs we put forward a universal interface tailoring strategy that introduces the mercapto compound as the intermediate cross-linked layer. The mercapto compound strongly interacts with the AgNWs, forming a dense protective layer on their surface to improve their corrosion resistance, and reacts with the polymer substrate, forming a buffer layer to release the concentrated stress. As a result, the optimized TSCs showed superior stretchability (160%), exceptional durability (230 000 cycles), competent optoelectrical performance (18.0 ohm·sq^-1 with a transmittance of 86.5%), and prominent stability. This work provides clear guidance and a strong impetus for the development of transparent stretchable electronics.

Revealing the Chemical Reaction Properties of a SiHCl3 Pyrolysis System by the ReaxFF Molecular Dynamics Method

The pyrolysis kinetics of SiHCl₃ and its reaction mechanism are essential for the chemical vapor deposition process in polysilicon industries. However, due to the high temperature and lack of in situ experimental detection technology, it is difficult to carry out experimental research on the pyrolysis kinetics of SiHCl₃. In this work, reactive force field molecular dynamics simulations of SiHCl₃ pyrolysis were performed to investigate the effect of temperature on the pyrolysis kinetics of SiHCl₃ at the atomistic scale in a wide temperature range (1000-2000 K). The lumped Si clusters containing more than five Si atoms tended to appear at the later period of the reaction under a temperature lower than 1300 K, some of which even possessed polycyclic structures; nevertheless, small ones with less than two Si atoms such as SiHCl₂ and HCl tended to emerge under a high temperature. The changes of partial energy terms with time evolution under various temperatures were proved to be rooted in the distribution of intermediates based on the momentary simulation period. In general, the reaction network at a low temperature was more complicated than that at a high temperature, resulting from the fact that more chemical events and intermediates came into existence, and the maximum number of Si atoms in one single molecule/radical was observed under a low temperature than that under a high temperature. As to the variation of SiHCl₃ with the progress of the reaction, the linear fitting tendency disappeared under the temperature above 1300 K, which changed in fluctuation with the further elevation of temperature, elucidating the fact that SiHCl₃ can act as a product and not just as a reactant to participate in elementary chemical events frequently.

Failing Forward: Stability of Transparent Electrodes Based on Metal Nanowire Networks

Metal nanowire (MNW)-based transparent electrode technologies have significantly matured over the last decade to become a prominent low-cost alternative to indium tin oxide (ITO). Beyond reaching the same level of performance as ITO, MNW networks offer additional advantages including flexibility and low materials cost. To facilitate adoption of MNW networks as a replacement to ITO, they must overcome their inherent stability issues while maintaining their properties and cost-effectiveness. Herein, the fundamental failure mechanisms of MNW networks are discussed in detail. Recent strategies to computationally model MNWs from the nano- to macroscale and suggest future work to capture dynamic failure to unravel mechanisms that account for convolution of the failure modes are highlighted. Strategies to characterize MNW network failure in situ and postmortem are also discussed. In addition, recent work about improving the stability of MNW networks via encapsulation is discussed. Lastly, a perspective is given on how to frame the requirements of MNW-encapsulant hybrids with reference to their target applications, namely: solar cells, transparent film heaters, sensors, and displays. A cost analysis to comment on the feasibility of implementing MNW hybrids is provided, and critical areas to focus on for future work on MNW networks are suggested.