Building two-dimensional materials one row at a time: Avoiding the nucleation barrier

Abstract

Assembly of two-dimensional (2D) molecular arrays on surfaces produces a wide range of architectural motifs exhibiting unique properties, but little attention has been given to the mechanism by which they nucleate. Using peptides selected for their binding affinity to molybdenum disulfide, we investigated nucleation of 2D arrays by molecularly resolved in situ atomic force microscopy and compared our results to molecular dynamics simulations. The arrays assembled one row at a time, and the nuclei were ordered from the earliest stages and formed without a free energy barrier or a critical size. The results verify long-standing but unproven predictions of classical nucleation theory in one dimension while revealing key interactions underlying 2D assembly.

The Synthesis of Sub-Nano-Thick Pd Nanobelt–Based Materials for Enhanced Hydrogen Evolution Reaction Activity

“…Pd(0.9) and Pd(0.7) performances were similar, while the addition of Pt into Pd NBs with the generation of PdPt NBs caused dramatic activity enhancement. Besides, the eePt 6o Pd 40 NBs showed much larger current density, compared to any of the above samples, including the benchmark Pt/C catalysts, yielding current densities at −0.1 V for eePt 60 Pd 40 NBs, eePt 35 Pd 65 NBs, and Pt/C equal to −17.71, −9.09, and −9.39 A/m 2 ECSA(Pd+Pt) , respectively. Furthermore, the mass activities ( Figure 6b) at −0.1 V of eePt 60 Pd 40 , eePt 35 Pd 65 NBs, and Pt/C were −1852, −834, and −1000 mA/mg Pd+Pt , respectively.…”

“…Besides, the eePt 6o Pd 40 NBs showed much larger current density, compared to any of the above samples, including the benchmark Pt/C catalysts, yielding current densities at −0.1 V for eePt 60 Pd 40 NBs, eePt 35 Pd 65 NBs, and Pt/C equal to −17.71, −9.09, and −9.39 A/m 2 ECSA(Pd+Pt) , respectively. Furthermore, the mass activities ( Figure 6b) at −0.1 V of eePt 60 Pd 40 , eePt 35 Pd 65 NBs, and Pt/C were −1852, −834, and −1000 mA/mg Pd+Pt , respectively. When the currents were normalized by pure Pt loading, the generated Pt 15 Pd 85 , eePt 35 Pd 65 , and eePt 60 Pd 40 NBs all exhibited much higher currents, compared with that of the pure Pt.…”

“…We attributed this difference to the possibility of the pure Pd catalysts encountering severe over-hydrogenation under potential deposition to form PdH 2 , which might lead to the loss of catalytic selectivity. The I o of Pt 15 Pd 85 , eePt 60 Pd 40 , and eePt 35 Pd 65 NBs were 0.19, 0.44, and 0.70 mA/cm 2 ECSA(Pd+Pt) , were respectively, 0.95, 2.2, and 3.5 times higher than that of pure Pt catalysts (0.20 mA/cm 2 ). Although Pd(0.7) and Pd(0.9) showed higher exchange current, compared with Pd black, based on their mass activities, they nonetheless, showed lower I 0 owing to their larger ECSAs.…”

On Simulating the Formation of Structured, Crystalline Systems via Non-classical Pathways

“…Similar imaging techniques could be used to measure the evolution of the free energy of amorphous clusters in these bidisperse, attractive colloidal systems based on analysis methods outlined in Dullens et al (2006). In addition, using total internal reflection microscopy or scanning probe methods it should be possible to identify the direct effects of the large particles on the detachment of small particles from the substrate (Ganapathy et al, 2010;Chen et al, 2019). We anticipate that the lessons learned by extensive study of these colloidal systems will ultimately shed light on molecular processes where crystallization occurs in the presence of unwanted impurities in solution.…”

Applications of ESEM on Materials Science: Recent Updates and a Look Forward

“…In recent years, in situ analysis has become an important research direction in the field of materials science, i.e., to observe and record dynamic physicochemical processes of materials in real‐time, so as to reflect more “process” information rather than traditional static observations either from “start point” or “end point.” The aim of in situ analysis is to clarify the mechanisms of interactions between materials and the environment that have not been clearly understood in the past. The in situ monitoring of dynamic processes, including in situ spectrum and in situ imaging, has gradually replaced the post‐mortem analysis or static observation and been applied more and more widely . Of course, in situ studies in materials research based on ESEM were also remarkably expanded in the past few years.…”