Near Infrared Light-Driven Photothermal Effect on Homochiral Au/TiO2 Nanotube Arrays for Enantioselective Desorption.

Chiral enantiomers have different effects on biological processes. Enantiomer separation is significant and necessary. Herein, a photothermal (PT) effect-derived enantioselective desorption strategy based on homochiral Au/TiO2 nanotubes (NTs) is developed. Using 3,4-dihydroxyphenylalanine (DOPA) as the model enantiomer, an obvious selective desorption of L/D-DOPA can be achieved by the NIR light-triggered local temperature enhancement. Molecular docking simulation further verifies that the distinct affinity precipitated by the different hydrogen bonds between homochiral sorbent and target enantiomers is the origin of enantioselective desorption. This desorption strategy provides a green and alternative approach for the selective separation of chiral molecules.

Exploiting Free-Standing p-CuO/n-TiO2 Nanochannels as a Flexible Gas Sensor with High Sensitivity for H2S at Room Temperature.

Hydrogen sulfide (H2S) is an extremely hazardous gas and is harmful to human health and the environment. Here, we developed a flexible H2S gas-sensing device operated at room temperature (25 °C) based on CuO nanoparticles coated with free-standing TiO2-nanochannel membranes that were prepared by simple electrochemical anodization. Benefiting from the modulated conductivity of the CuO/TiO2 p-n heterojunction and a unique nanochannel architecture, the traditional thermal energy was innovatively replaced with UV irradiation (λ = 365 nm) to provide the required energy for triggering the sensing reactions of H2S. Importantly, upon exposure to H2S, the p-n heterojunction is destroyed and the newly formed ohmic contact forms an antiblocking layer at the interface of CuS and TiO2, thus making the sensing device active at room temperature. The resulting CuO/TiO2 membrane exhibited a notable detection sensitivity for H2S featuring a minimum detection limit of 3.0 ppm, a response value of 46.81% against 100 ppm H2S gas, and a rapid response and recovery time. This sensing membrane also demonstrated excellent durability, long-term stability, and wide-range response to a concentration of up to 400 ppm in the presence of 40% humidity as well as outstanding flexibility and negligible change in electrical measurements under various mechanical stability tests. This study not only provides a new strategy to design a gas sensor but also paves a universal platform for sensitive gas sensing.

Wireless Battery-Free Generation of Electric Fields on One-Dimensional Asymmetric Au/ZnO Nanorods for Enhanced Raman Sensing.

Wearable electronics have great potential in enhancing health monitoring, disease diagnosis, and environmental pollution tracking. Development of wearable surface-enhanced Raman spectroscopy (SERS) substrates with target sampling and sensitive sensing functions is a promising way to obtain physical and chemical information. This study describes a facile and effective approach for constructing an electrically modulated SERS (E-SERS) substrate as a wearable and wireless battery-free substrate with improved sensitivity. By integrating zinc oxide nanorods (ZnO NRs) with asymmetric gold decoration, controllable enhanced piezoelectric potentials were achieved using magnets to supply the adjustable pressure force. Owing to spatially oriented electron-hole pair separation on the asymmetric NRs, the local hotspot intensity at the Au tips is significantly improved, increasing the SERS signal by 6.7 times. This mechanism was quantitatively analyzed using Raman spectra by in situ formation of Prussian blue (PB). As a proof-of-concept, the E-SERS substrate was further used as a wearable flexible device to directly collect the sweat on a runner's skin and then monitor the lactate status of the runner. This study offers new insight into the development of E-SERS substrates and provides new design options for the construction of wearable sampling and sensing devices for the noninvasive monitoring of metabolites in healthcare and biomedical fields.

In Situ Monitoring of the "Point Discharge" Induced Antibacterial Process by the Onsite Formation of a Raman Probe.

Electroporation induced by the "point discharge" effect is an effective technique for bacteria inactivation. Rapidly monitoring the electroporation-induced inactivation process is important for screening nanomaterials with high antimicrobial performance. In this study, we develop a facile strategy to in situ monitor the electroporation induced antimicrobial mechanism based on the surface-enhanced Raman scattering (SERS) effect of the Au-nanotip arrays. Owning to the high local-electric field (∼107 V m-1) generated on the Au nanotips, the bacteria are rapidly electroporated and effectively inactivated with ≥99.9% reduction in bacteria colony counts by only applying an external voltage of +0.8 V for 10 s. The related inactivation mechanism is directly verified by the formation of the Prussian blue (PB) nanocrystals by leaking of the uptaken [Fe(CN)6]3- ions from the cleavage area on the cell membrane. These [Fe(CN)6]3- ions react with Fe2+ to form PB nanocrystals onsite as soon as they leak out. The characteristic peak of PB in the cellular Raman-silent region provides a collective monitoring approach for the destruction of microorganisms. The present strategy not only develops a facial method for future use in evaluating electroporation materials, but also paves a rapid way for offering accurate information on some antibacterial and antitumor processes.

Asymmetric coupling of Au nanospheres on TiO2 nanochannel membranes for NIR-gated artificial ionic nanochannels.

Au nanoparticles were asymmetrically fabricated at one tip of TiO2 nanochannels by combining a photocatalytic reaction and limited penetration of light. Using the asymmetrical nanochannel-based membrane as a plasma absorber, near-infrared-gated artificial ionic nanochannels were designed.