中央研究院 原子與分子科學研究所

We here demonstrate the multifunctional properties of atomically thin heterojunctions that are enabled by strong interfacial interactions and their integration into ultra-high performance, self-powered sensors. Epitaxial alignment between tin diselenide and graphene through direct growth produces thermoelectric and mechanoelectric properties beyond the ability of either component. An unprecedented ZT of 2.43 originated from the synergistic combination of graphene’s high carrier conductivity and SnSe2 mediated thermal conductivity lowering. Moreover, strong interaction at the SnSe₂/graphene interface produces stress localization that results in a novel 2D-crack-assisted strain sensing mechanism whose sensitivity (GF=450) is superior to all other 2D materials. Finally, the graphene-assisted growth process, permits the formation of high-quality heterojunctions directly on polymeric substrates for flexible and transparent self-powered sensors that achieve fast and reliable strain sensing from a small temperature gradient. Our work enhances the fundamental understanding of multifunctionality at the atomic scale and provide a route towards structural health monitoring through ubiquitous and smart devices.

The dynamics of DNA double-strand break (DSB) repairs including homology-directed repair and nonhomologous end joining play an important role in diseases and therapies. However, investigating DSB repair is typically a low-throughput and cross-sectional process, requiring disruption of cells and organisms for subsequent nuclease-, sequencing- or reporter-based assays. In this protocol, we provide instructions for establishing a bioluminescent repair reporter system using engineered Gaussia and Vargula luciferases for noninvasive tracking of homology-directed repair and nonhomologous end joining, respectively, induced by SceI meganuclease, SpCas9 or SpCas9 D10A nickase-mediated editing. We also describe complementation with orthogonal DSB repair assays and omics analyses to validate the reporter readouts. The bioluminescent repair reporter system provides longitudinal and rapid readout (~seconds per sample) to accurately and efficiently measure the efficacy of genome-editing tools and small-molecule modulators on DSB repair. This protocol takes ~2–4 weeks to establish, and as little as 2 h to complete the assay. The entire bioluminescent repair reporter procedure can be performed by one person with standard molecular biology expertise and equipment. However, orthogonal DNA repair assays would require a specialized facility that performs Sanger sequencing or next-generation sequencing.

Shift current is a direct current generated from nonlinear light–matter interaction in a noncentrosymmetric crystal and is considered a promising candidate for next-generation photovoltaic devices. The mechanism for shift currents in real materials is, however, still not well understood, especially if electron–hole interactions are included. Here, we employ a first-principles interacting Green’s-function approach on the Keldysh contour with real-time propagation to study photocurrents generated by nonlinear optical processes under continuous wave illumination in real materials. We demonstrate a strong direct current shift current at subbandgap excitation frequencies in monolayer GeS due to strongly bound excitons, as well as a giant excitonic enhancement in the shift current coefficients at above bandgap photon frequencies. Our results suggest that atomically thin two-dimensional materials may be promising building blocks for next-generation shift current devices.

Complex vibrational features of solvated hydronium ion, H₃O⁺, in 3 μm enable us to look into the vibrational coupling among O-H stretching modes and other degrees of freedom. Two anharmonic coupling schemes have often been engaged to explain observed spectra: coupling with OH bending overtone, known as Fermi resonance (FR), has been proposed to account for the splitting of the OH stretch band at ~3300 cm^-1 in H₃O⁺…Ar₃, but an additional peak in H₃O⁺…(N₂)₃ at the similar frequency region has been assigned to a combination band (CB) with the low-frequency intermolecular stretches. While even stronger vibrational coupling is expected in H₃O⁺…(H₂O)₃, such pronounced peaks are absent. In the present study, vibrational spectra of H₃O⁺…Kr₃ and H₃O⁺…(CO)₃ are measured to complement the existing spectra. Using ab initio anharmonic algorithms, we are able to assign the observed complex spectral features, to resolve seemingly contradictory notions in the interpretations, and to reveal simple pictures of the interplay between FR and CB.

Experimental infrared spectra between 2600 to 3800 cm^-1 for a series of asymmetric proton bound dimers with protonated trimethylamine (TMA–H⁺) as the proton donor were recorded and analyzed. Based on conventional wisdom, the frequency of the N-H⁺ stretching mode is expected to red shift as the proton affinity of proton acceptors (Ar, N₂, CO, C₂H₂, H₂O, CH₃OH, and C₂H₅OH) increases. The observed band, however, shows a peculiar splitting of ≈300 cm^-1 with the intensity shifting pattern resembling a two-level system. Theoretical investigation based on ab initio anharmonic algorithms reveals that the observed band splitting and its extraordinarily large gap of ≈300 cm^-1 is a result of strong coupling between fundamental of the proton stretching mode and overtone states of the two proton bending modes, that is commonly known as Fermi resonance (FR). We also provide a simple and general theoretical model to link the strong FR coupling to the quasi-two-level system behavior in the observed band intensity. Since the model does not depend on the molecular specification of TMA–H⁺, the strong coupling we observed here is an intrinsic property associated with proton motions in a wide range of molecular systems.