Bertram John R, Ding Yuchen, Nagpal Prashant
Materials Science and Engineering, University of Colorado Boulder USA
Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder USA.
Nanoscale Adv. 2020 Apr 24;2(6):2363-2370. doi: 10.1039/d0na00017e. eCollection 2020 Jun 17.
Living nano-biohybrid organisms or nanorgs combine the specificity and well-designed surface chemistry of an enzyme catalyst site, with the strong light absorption and efficient charge injection (for biocatalytic reaction) from inorganic materials. Previous efforts in harvesting sunlight for renewable and sustainable photochemical conversion of inexpensive feedstocks to biochemicals using nanorgs focused on the design of semiconductor nanoparticles or quantum dots (QDs). However, metal nanoparticles and nanoclusters (NCs), such as gold (Au), offer strong light absorption properties and biocompatibility for potential application in living nanorgs. Here we show that optimized, sub-1 nanometer Au NCs-nanorgs can carry out selective biochemical catalysis with high turnover number (10 mol mol of cells) and turnover frequency (>2 × 10 h). While the differences of size, light absorption, and electrochemical properties between these NCs (with 18, 22, and 25 atoms) are small, large differences in their light-activated properties dictate that 22 atom Au NCs are best suited for forming living nanorgs to drive photocatalytic ammonia production from air. Based on our experiments, these Au NC-nanorgs demonstrate 29.3% quantum efficiency of converting absorbed photons to the desired chemical, and 12.9% efficiency of photon-to-fuel conversion based on energy input-output. Further, by comparing the light-driven ammonia production yield between strains producing Mo-Fe nitrogenase with and without histidine tags, we demonstrate that preferential coupling of Au NCs to the nitrogenase through Au-histidine interactions is crucial for effective electron transfer and subsequent product generation. Together, these results provide the design rules for forming Au NCs-nanorgs and can have important implications for carrying out light-driven biochemical catalysis for renewable solar fuel generation.
活的纳米生物杂交体或纳米机体将酶催化位点的特异性和精心设计的表面化学与无机材料的强光吸收和高效电荷注入（用于生物催化反应）结合在一起。此前利用纳米机体将廉价原料进行可再生且可持续的光化学转化以生成生物化学品的研究主要集中在半导体纳米颗粒或量子点（QD）的设计上。然而，金属纳米颗粒和纳米团簇（NC），如金（Au），具有强光吸收特性和生物相容性，在活的纳米机体中具有潜在应用价值。在此我们表明，优化后的亚1纳米金纳米团簇 - 纳米机体能够以高周转数（每摩尔细胞10摩尔）和周转频率（>2×10⁵ h⁻¹）进行选择性生化催化。虽然这些纳米团簇（含18、22和25个原子）在尺寸、光吸收和电化学性质上差异较小，但它们的光激活性质差异很大，这表明22原子的金纳米团簇最适合形成活的纳米机体以驱动空气中光催化制氨。基于我们的实验，这些金纳米团簇 - 纳米机体将吸收的光子转化为所需化学品的量子效率为29.3%，基于能量输入 - 输出的光子到燃料的转化效率为12.9%。此外，通过比较产生带有和不带有组氨酸标签的钼铁固氮酶的菌株之间的光驱动产氨量，我们证明金纳米团簇通过金 - 组氨酸相互作用与固氮酶的优先偶联对于有效的电子转移和随后的产物生成至关重要。总之，这些结果为形成金纳米团簇 - 纳米机体提供了设计规则，对于开展光驱动生物催化以生成可再生太阳能燃料具有重要意义。
