Apt-Conjugated PDMS-ZnO/Ag-Based Multifunctional Integrated Superhydrophobic Biosensor with High SERS Activity and Photocatalytic Sterilization Performance.

Sensitive detection and efficient inactivation of pathogenic bacteria are crucial for halting the spread and reproduction of foodborne pathogenic bacteria. Herein, a novel Apt-modified PDMS-ZnO/Ag multifunctional biosensor has been developed for high-sensitivity surface-enhanced Raman scattering (SERS) detection along with photocatalytic sterilization towards Salmonella typhimurium (S. typhimurium). The distribution of the electric field in PDMS-ZnO/Ag with different Ag sputtering times was analyzed using a finite-difference time-domain (FDTD) algorithm. Due to the combined effect of electromagnetic enhancement and chemical enhancement, PDMS-ZnO/Ag exhibited outstanding SERS sensitivity. The limit of detection (LOD) for 4-MBA on the optimal SERS substrate (PZA-40) could be as little as 10-9 M. After PZA-40 was modified with the aptamer, the LOD of the PZA-40-Apt biosensor for detecting S. typhimurium was only 10 cfu/mL. Additionally, the PZA-40-Apt biosensor could effectively inactivate S. typhimurium under visible light irradiation within 10 min, with a bacterial lethality rate (Lb) of up to 97%. In particular, the PZA-40-Apt biosensor could identify S. typhimurium in food samples in addition to having minimal cytotoxicity and powerful biocompatibility. This work provides a multifunctional nanoplatform with broad prospects for selective SERS detection and photocatalytic sterilization of pathogenic bacteria.

A novel strategy for specific sensing and inactivation of Escherichia coli: Constructing a targeted sandwich-type biosensor with multiple SERS hotspots to enhance SERS detection sensitivity and near-infrared light-triggered photothermal sterilization performance.

Human health is greatly threatened by bacterial infection, which raises the risk of serious illness and death in humans. For early screening and accurate treatment of bacterial infection, there is a strong desire to undertake ultrasensitive detection and effective killing of pathogenic bacteria. Herein, a novel surface-enhanced Raman scattering (SERS) biosensor based on sandwich structure consisting of capture probes/bacteria/SERS tags was established for specific identification, capture and photothermal killing of Escherichia coli (E. coli). Finite-difference time-domain (FDTD) technique was used to simulate the electromagnetic field distribution of capture probes, SERS tags and sandwich-type SERS substrate, and a possible SERS enhancement mechanism based on sandwich structure was presented and discussed. Sandwich-type SERS biosensor successfully achieved distinctive identification and magnetic beneficiation of E. coli. In addition, a single SERS substrate, including capture probes and SERS tags, could also achieve outstanding photothermal effects as a consequence of localized surface plasmon resonance (LSPR) effect. Intriguingly, sandwich-type SERS biosensor demonstrated a higher photothermal conversion efficiency (50.03 %) than the single substrate, which might be attributed to the formation of target bacterial clusters. The superior biocompatibility and the low toxicity of the sandwich-type biosensor were confirmed. Our approach offers a fresh method for constructing sandwich-type biosensor with multiple SERS hotspots based on extremely effective hybrid plasmonic nanoparticles, and has a wide range of potential applications in the recognition and treatment of bacteria.

Further Boosting Solar Cell Performance via Bandgap-Graded Ag Doping in Cu2ZnSn(S,Se)4 Solar Cells Compared to Uniform Ag Doping.

Cu2ZnSn(S,Se)4 (CZTSSe) is a hopeful substitution to commercialized Cu(In,Ga)Se2 (CIGSe) devices with similar structure and optoelectronic properties and has advantages of nontoxicity, low cost, and abundant reserves. However, the traditional flat bandgap structure of the CZTSSe absorber layer does not efficiently enhance the collection of photogenerated electrons and decrease recombination. Graded bandgap engineering toward the interfaces of CIGSe solar cells is the key to realize high-efficiency devices. In this study, we obtained (Cu1-xAgx)2ZnSn(S,Se)4 (CAZTSSe) absorber layers with high-concentration Ag doping at both ends of the absorption layer and undoped or low-concentration Ag doping in the middle part through a new miscible layered precursor method. This bandgap structure suppressed CuZn defects, delayed Fermi level pinning near the CZTSSe/CdS interface, sustained good electrical conductivity and light absorption in the middle of the absorption layer, improved the conversion efficiency of incident light, and inhibited recombination of carriers toward the Mo back electrode. In addition, we also compared the performance of undoped, uniformly Ag-doped, and V-type Ag-doped CZTSSe devices to acquire a deeper understanding of the reasons for the enhanced performance. It can be found that compared with undoping, the open-circuit voltage (Voc) of the best devices with uniform doping (x = 15%) increased from 379 to 386 mV, the fill factor (FF) increased from 44.70 to 54.14%, and the photoelectric conversion efficiency (PCE) increased from 4.63 to 6.21%. More surprisingly, the Voc of the optimal CAZTSSe devices (sample D) with Ag-graded doping was increased to 413 mV and the FF was increased to 59.63%. It also achieved an impressive PCE of 7.35%. The above results prove the importance of tuning Ag gradient doping of CZTSSe films for improving solar cell performance.