From Transistors to Phototransistors by Tailoring the Polymer Stacking

It is universally acknowledged that highly photosensitive transistors are strongly dependent on the high carrier mobility of polymer-based semiconductors. However, the polymer π–π stacking and aggregation, required to increase the charge mobility, conversely inhibit the dissociation of photogenerated charge carriers, in turn accelerating the geminate recombination of electron-hole pairs. To explore the effects of charge mobility and polymer stacking on the photoresponsivity of the phototransistors, here, two alternating copolymers are synthesized, namely P-PPAB-IDT and P-PPAB-BDT, by palladium-catalyzed Stille coupling of PPAB with indaceodithiophene (IDT) or benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl) (BDT) monomers. The polymer P-PPAB-IDT demonstrates a nearly 20 times enhancement in the hole mobility compared to P-PPAB-BDT. Yet, P-PPAB-IDT surprisingly shows no response to white light illumination, whereas P-PPAB-BDT exhibits a significant photoresponse to the same light source with a high light-current/dark-current (Ilight/Idark) ratio of 21.6 in the p-type area and a low current ratio of just 5.2 in the n-type area. It is believed that this work will provide an effective strategy to develop highly photosensitive polymer semiconductors by reducing polymer stacking and aggregation rather than improving the charge carrier mobility.acceptedVersionPeer reviewe

Nano friction behaviour between magnetic materials and copper considering the inter-diffusion effect

AbstractCopper, permalloy, cobalt, and silicon are the materials that have been widely utilised in magnetic devices. When the size of interest is down to the nanoscale, the inter-diffusion between certain materials becomes influential. This paper studies the nanoscale friction characteristics between frictional pairs with and without inter-diffusion properties through the atomic force microscope. The distinct evolution features of nanoscale friction force when inter-diffusion is involved are discovered experimentally, which is also confirmed through theoretical analysis. Firstly, through the thin film deposition method, four pairs of contact materials (Cu–Ni81Fe19, Si–Ni81Fe19, Cu–Co, Cu–Si) are designed for friction tests, in which diffusion occurs at the interface of Cu–Ni81Fe19 pair. Then, the effects of sliding velocity and loading force on the nano friction of each pair are measured. It is found that regardless of the diffusion phenomenon: (1) the adhesion force values exhibit a notable correlation to the values of the friction force; (2) the friction force in all four material pairs consistently increases with the growth of the normal loading force, although the growth rate may differ. In terms of the sliding velocity effect, the friction forces of immiscible materials (Si–Ni81Fe19, Cu–Co, and Cu–Si) are found to increase with the increasing sliding velocity. However, the friction force of Cu–Ni81Fe19, decreases with the increasing sliding velocity. Furthermore, a compositive friction model considering both the velocity and the normal force effect was proposed, which shows good agreement with the experimental results and explains the nano friction behaviour of both miscible and immiscible metals. </jats:p

Ultraspecific One-Pot CRISPR-Based “Green-Yellow-Red” Multiplex Detection Strategy Integrated with Portable Cartridge for Point-of-Care Diagnosis

Versatile, informative, sensitive, and specific nucleic acid detection plays a crucial role in point-of-care pathogen testing, genotyping, and disease monitoring. In this study, we present a novel one-pot Cas12b-based method coupled with the “Green-Yellow-Red” strategy for multiplex detection. By integrating RT-LAMP amplification and Cas12b cleavage in a single tube, the entire detection process can be completed within 1 h. Our proposed method exhibits high specificity, enabling the discrimination of single-base mutations with detection sensitivity approaching single molecule levels. Additionally, the fluorescent results can be directly observed by the naked eye or automatically analyzed using our custom-designed software Result Analyzer. To realize point-of-care detection, we developed a portable cartridge capable of both heating and fluorescence excitation. In a clinical evaluation involving 20 potentially SARS-CoV-2-infected samples, our method achieved a 100% positive detection rate when compared to standard RT-PCR. Furthermore, the identification of SARS-CoV-2 variants using our method yielded results that were consistent with the sequencing results. Notably, our proposed method demonstrates excellent transferability, allowing for the simultaneous detection of various pathogens and the identification of mutations as low as 0.5% amidst a high background interference. These findings highlight the tremendous potential of our developed method for molecular diagnostics