Superhydrophobic coatings have tremendous potential for applications in different fields and have been achieved commonly by increasing nanoscale roughness and lowering surface tension. Limited by the availability of either ideal nano-structural templates or simple fabrication procedures, the search of superhydrophobic coatings that are easy to manufacture and are robust in real-life applications remains challenging for both academia and industry. Herein, we report an unconventional protocol based on a single-step, stoichiometrically controlled reaction of long-chain organosilanes with water, which creates micro- to nano-scale hierarchical siloxane aggregates dispersible in industrial solvents (as the coating mixture). Excellent superhydrophobicity (ultrahigh water contact angle >170° and ultralow sliding angle <1°) has been attained on solid materials of various compositions and dimensions, by simply dipping into or spraying with the coating mixture. It has been demonstrated that these complete waterproof coatings hold excellent properties in terms of cost, scalability, robustness, and particularly the capability of encapsulating other functional materials (e.g. luminescent dyes).
Modern smartphone-based sensing devices are generally standalone detection platforms that can transduce signals (via the built-in USB port, audio jack, or camera), perform analysis through mobile applications (apps), and display results on the screen/user interface. The advancement toward this ultimate form of on-site chemical analysis and point-of-care diagnosis is tied closely with the evolution of mobile technology. Previous reviews in the field mainly focused on the physical platforms while overlooking the role of mobile apps in such devices. There exist three general stages throughout the development: (1) early generation telemedicine, (2) mobile phone-assisted clinical diagnosis (without apps), and (3) mobile app-based sensing devices for various analytes. This review presents the key breakthroughs during each stage, recent development, remaining challenges, and future perspectives of the field. Representative examples, spanning from the pioneering point-of-care testing to the latest devices with integrated mobile apps, are classified by their sensing mechanisms. The review also discusses the scarcity of open-source apps dedicated to molecular sensing. With the introduction of more open-source and commercial apps, the mobile app-based detection system is anticipated to dominate point-of-care diagnosis and on-site molecular sensing in our opinion.
Molecularly tunable metal-semiconductor (MS) junctions have been fabricated by modifying mercury drop electrodes with n-alkanethiols, 1-CH 3 (CH 2 ) n−1 SH (n = 10,11,12,14,16,and 18) prior to the formation of intimate contact with hydrogen-terminated silicon (H-Si) and characterized by both solid-state electrical and electrochemical measurements. We have demonstrated that the current-voltage properties of these molecular junctions change with time and that diverse time-dependent progression "patterns" were observed between the systems of long-chain alkanethiols (C14SH, C16SH, and C18SH) and shortchain alkanethiols (C10SH, C11SH, and C12SH). It is remarkable that for mercury contact electrodes modified with long-chain alkanethiolate self-assembled monolayers (SAMs), the junctions became more rectifying and stabilized over a prolonged period (∼2 h). For short-chain counterparts, surprisingly, they initially became more rectifying, then changed to ohmic over a similar period. It was proposed that at the MS interface, short-chain alkanethiolate SAMs first reorganize to be more ordered before eventually collapse. Long-chain alkanethiolate SAMs, on the other hand, achieve a more uniform, oriented, and stable packing as time goes by. These novel findings shed light on "long-term" intermolecular interactions that drive molecular systems to undergo ultraslow reorganizations, which can be readily modulated by simply varying the precursor structures (e.g., chain length of n-alkanethiols).
The effect of molecular dipoles on charge transport across organic monolayer-modified metal−semiconductor junctions has been investigated systematically. We have prepared a new set of organic monolayers with varied terminal derivatization on crystalline silicon to construct molecular junctions using mercury drops as the top contact electrode. Although the surface and structural characterization indicated the high quality and uniformity of all these monolayers, the junctions (Hg/R−Si�) showed a diverse electrical performance. Beyond taking the most common theoretical approach to analyze these molecular junctions, that is, applying the thermionic emission model (TE) to calculate the barrier height (Φ B ) and ideality factor (η), we have examined the contribution of the carrier generation−recombination (CGR) mechanism by fitting the experimental current−voltage curves. When η is close to unity, the charge transport across these molecular junctions is dominated by TE; for η values greater than unity, TE indeed remains the dominant current transport pathway, while CGR transport becomes significant.
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