Bacteria Inspired Internal Standard SERS Substrate for Quantitative Detection.

Metal-respiring bacteria are frequently used to recycle metal resources by biosynthesizing nanoparticles on its surface in environment treatment. However, further utilization of biogenetic nanoparticles through combining the advantages of both bacteria and nanoparticles is still limited. Herein, biogenetic Au@Ag nanoislands are utilized as the surface-enhanced Raman spectroscopy (SERS) substrate for quantitative detection. Specifically, Au@Ag nanoislands enhance the Raman signal via surface plasmon resonance, while biomolecules (phospholipid, tyrosine, and phenylalanine, etc.) on bacterium serve as an internal standard to eliminate the discrepancy of the target SERS intensity in different hot spots. Gene-controlled biomolecules in bacteria guarantee the reproducibility of this SERS substrate. The generality of this analytical method is demonstrated by determining rhodamine 6G, malachite green, and uric acid. This discovery solves a pervasive problem in SERS analysis through a simple biogenetic nanosystem, which opens up an avenue to address scientific challenges by using versatile organisms from nature.

Microbial synthesis of highly dispersed PdAu alloy for enhanced electrocatalysis.

Biosynthesis based on the reducing capacity of electrochemically active bacteria is frequently used in the reduction of metal ions into nanoparticles as an eco-friendly way to recycle metal resources. However, those bionanoparticles cannot be used directly as electrocatalysts because of the poor conductivity of cell substrates. This problem was solved by a hydrothermal reaction, which also contributes to the heteroatom doping and alloying between Pd and Au. With the protection of graphene, the aggregation of nanoparticles was successfully avoided, and the porous structure was maintained, resulting in better electrocatalytic activity and durability than commercial Pd/C under both alkaline (CH3CH2OH, 6.15-fold of mass activity) and acidic (HCOOH, 6.58-fold of mass activity) conditions. The strategy developed in this work opens up a horizon into designing electrocatalysts through fully utilizing the abundant resources in nature.