Two-dimensional van der Waals heterojunctions can significantly boost gas-sensing performance through interfacial synergy, surpassing the limits of individual constituents. Based on first-principles calculations, this study systematically explores the potential of a vertical heterojunction composed of novel Janus MoTeSe and InN for gas-sensing applications. Binding-energy calculations and AIMD simulations identify AB-MoIn-stacked MoTeSe/InN as the most stable configuration, and the adsorption behavior and sensing mechanism of the heterojunction toward Cl₂, NO₂, NH₃, NO, SO₂, and H₂S are investigated comprehensively. The results reveal that the heterojunction markedly enhances adsorption of Cl₂, NO₂, NO, and H₂S, with adsorption energies of -0.880 eV and -0.961 eV for Cl₂ and NO₂, respectively, accompanied by substantial charge transfer. Electronic-structure analysis elucidates the key sensing mechanisms: adsorption of NO₂ (T In site) and NO metallizes the system, greatly increasing electrical conductivity; adsorption of Cl₂ (TN site) and SO₂ increases the bandgap by approximately 47.3 % and 49.4 %, respectively; notably, NO₂ adsorption on the Te site also induces magnetism. Further evaluation of sensitivity and recovery time indicates that the heterojunction exhibits both high sensitivity and good reversibility toward NO₂ and Cl₂—for example, the room-temperature recovery time for NO₂ on the Te site is only 0.36 ms. This work clarifies the atomic-scale gas-sensing mechanism of MoTeSe/InN heterostructures, especially for Cl₂ and NO₂, and provides a solid theoretical basis for their application as high-performance, recyclable gas-sensor candidates.

This work aims to fabricate polymeric thin films with helically deployed gold (Au) nanoparticles by using self-assembled chiral block copolymers (BCPs*) with controlled helicity as templates, giving polymeric monolith with unique optical properties as chiral plasmonic thin film. Enantiomeric polylactide-based BCPs*, polystyrene-block-poly(L-lactide) (PS-b-PLLA) and poly-styrene-block-poly(D-lactide) (PS-b-PDLA) with disulfide junction are designed and synthesized, denoted as PS-ss-PLLA and PS-ss-PDLA, respectively. The helically deployed chemical junctions of the PS-ss-PLLA and PS-ss-PDLA thin films from the self-assembly of helix-forming BCPs* can give thiol end groups preferentially arranged in a one-handed helical fashion at the inner wall of nanoporous PS after hydrolysis of polylactide followed by reducing the disulfide into thiol. Au nanoparticles (Au NPs) with a size of 2-5 nm, resulting from reduction, can associate with the thiol end groups in the nanoporous PS, forming a helical disposition of Au NPs with specific handedness. As a result, circular dichroism (CD) signals of localized surface plasmonic resonance (LSPR) originating from the helical Au NP arrays with preferred chirality can be acquired from the polymeric monolith fabricated, giving appealing applications as chiroptical devices.