The interpretation of mechanisms governing hot carrier reactivity on metallic nanostructures is critical, yet elusive, for advancing plasmonic photocatalysis. In this work, we explored the influence of the diffusion of molecules on the hot carrier extraction rate at the solid-liquid interface, which is of fundamental interest for increasing the efficiency of photodevices. Through a spatially defined scanning photoelectrochemical microscopy investigation, we identified a diffusion-controlled regime hindering the plasmon-driven photochemical activity of metallic nanostructures. Using low-power monochromatic illumination (<2 W cm-2), we unveiled the hidden influence of mass transport on the quantum efficiency of plasmonic photocatalysts. The availability of molecules at the solid-liquid interface directly limits the extraction of hot holes, according to their nature and energy, at the reactive spots in Au nanoislands on an ultrathin TiO2 substrate. An intriguing question arises: does the mass transport enhancement caused by thermal effects unlock the reactivity of nonthermal carriers under steady state?

CEET Nanotechnology Centre VŠB Technical University of Ostrava 17 Listopadu 2172 15 Ostrava Poruba 708 00 Czech Republic

Czech Advanced Technology and Research Institute Regional Centre of Advanced Technologies and Materials Department Palacký University Olomouc Šlechtitelů 27 Olomouc 78371 Czech Republic

Department of Chemistry and NIS Centre University of Turin Turin 10125 Italy

See more in PubMed

Mukherjee S.; Libisch F.; Large N.; Neumann O.; Brown L. V.; Cheng J.; Lassiter J. B.; Carter E. A.; Nordlander P.; Halas N. J. Hot Electrons Do the Impossible: Plasmon-Induced Dissociation of H2 on Au. Nano Lett. 2013, 13 (1), 240–247. 10.1021/nl303940z. PubMed DOI

Zhang Y.; He S.; Guo W.; Hu Y.; Huang J.; Mulcahy J. R.; Wei W. D. Surface-Plasmon-Driven Hot Electron Photochemistry. Chem. Rev. 2018, 118 (6), 2927–2954. 10.1021/acs.chemrev.7b00430. PubMed DOI

Zhang C.; Jia F.; Li Z.; Huang X.; Lu G. Plasmon-Generated Hot Holes for Chemical Reactions. Nano Res. 2020, 13 (12), 3183–3197. 10.1007/s12274-020-3031-2. DOI

Mubeen S.; Lee J.; Singh N.; Krämer S.; Stucky G. D.; Moskovits M. An Autonomous Photosynthetic Device in Which All Charge Carriers Derive from Surface Plasmons. Nat. Nanotechnol. 2013, 8, 247–251. 10.1038/nnano.2013.18. PubMed DOI

Swaminathan S.; Rao V. G.; Bera J. K.; Chandra M. The Pivotal Role of Hot Carriers in Plasmonic Catalysis of C-N Bond Forming Reaction of Amines. Angew. Chem., Int. Ed. 2021, 60 (22), 12532–12538. 10.1002/anie.202101639. PubMed DOI

Baffou G.; Cichos F.; Quidant R. Applications and Challenges of Thermoplasmonics. Nat. Mater. 2020, 19 (9), 946–958. 10.1038/s41563-020-0740-6. PubMed DOI

Mascaretti L.; Naldoni A. Hot Electron and Thermal Effects in Plasmonic Photocatalysis. J. Appl. Phys. 2020, 128 (4), 041101.10.1063/5.0013945. DOI

Brongersma M. L.; Halas N. J.; Nordlander P. Plasmon-Induced Hot Carrier Science and Technology. Nat. Nanotechnol. 2015, 10 (1), 25–34. 10.1038/nnano.2014.311. PubMed DOI

Tian Y.; Tatsuma T. Mechanisms and Applications of Plasmon-Induced Charge Separation at TiO2 Films Loaded with Gold Nanoparticles. J. Am. Chem. Soc. 2005, 127 (20), 7632–7637. 10.1021/ja042192u. PubMed DOI

Kontoleta E.; Tsoukala A.; Askes S. H. C.; Zoethout E.; Oksenberg E.; Agrawal H.; Garnett E. C. Using Hot Electrons and Hot Holes for Simultaneous Cocatalyst Deposition on Plasmonic Nanostructures. ACS Appl. Mater. Interfaces 2020, 12 (32), 35986–35994. 10.1021/acsami.0c04941. PubMed DOI PMC

Wang S.; Gao Y.; Miao S.; Liu T.; Mu L.; Li R.; Fan F.; Li C. Positioning the Water Oxidation Reaction Sites in Plasmonic Photocatalysts. J. Am. Chem. Soc. 2017, 139 (34), 11771–11778. 10.1021/jacs.7b04470. PubMed DOI

Zhu H.; Xie H.; Yang Y.; Wang K.; Zhao F.; Ye W.; Ni W. Mapping Hot Electron Response of Individual Gold Nanocrystals on a TiO2 Photoanode. Nano Lett. 2020, 20 (4), 2423–2431. 10.1021/acs.nanolett.9b05125. PubMed DOI

Lee H.; Lee H.; Park J. Y. Direct Imaging of Surface Plasmon-Driven Hot Electron Flux on the Au Nanoprism/TiO2. Nano Lett. 2019, 19 (2), 891–896. 10.1021/acs.nanolett.8b04119. PubMed DOI

Cortés E.; Xie W.; Cambiasso J.; Jermyn A. S.; Sundararaman R.; Narang P.; Schlücker S.; Maier S. A. Plasmonic Hot Electron Transport Drives Nano-Localized Chemistry. Nat. Commun. 2017, 8, 14880.10.1038/ncomms14880. PubMed DOI PMC

Tatsuma T.; Nishi H. Plasmonic Hole Ejection Involved in Plasmon-Induced Charge Separation. Nanoscale Horiz. 2020, 5 (4), 597–606. 10.1039/C9NH00649D. PubMed DOI

Ogata R.; Nishi H.; Ishida T.; Tatsuma T. Visualization of Nano-Localized and Delocalized Oxidation Sites for Plasmon-Induced Charge Separation. Nanoscale 2021, 13 (2), 681–684. 10.1039/D0NR08552A. PubMed DOI

Hong F.; Wang S.; Zhang J.; Zhang B.; Sun K.; Huang J.; Qiao B.; Ta N.; Li M.; Li D.; Huang W.; Haruta M.; Li C. Blocking the Non-Selective Sites through Surface Plasmon-Induced Deposition of Metal Oxide on Au/TiO2 for CO-PROX Reaction. Chem. Catal. 2021, 1 (2), 456–466. 10.1016/j.checat.2021.04.003. DOI

Aizpurua J.; Ashfold M.; Baletto F.; Baumberg J.; Christopher P.; Cortes E.; de Nijs B.; Diaz Fernandez Y.; Gargiulo J.; Gawinkowski S.; Halas N.; Hamans R.; Jankiewicz B.; Khurgin J.; Kumar P. V.; Liu J.; Maier S.; Maurer R. J.; Mount A; Mueller N. S.; Oulton R.; Parente M.; Park J. Y.; Polanyi J.; Quiroz J.; Rejman S.; Schlucker S.; Schultz Z.; Sivan Y.; Tagliabue G.; Thangamuthu M.; Torrente-Murciano L.; Xiao X.; Zayats A.; Zhan C. Dynamics of Hot Electron Generation in Metallic Nanostructures: General Discussion. Faraday Discuss. 2019, 214 (0), 123–146. 10.1039/C9FD90011J. PubMed DOI

Cortés E.; Besteiro L. V.; Alabastri A.; Baldi A.; Tagliabue G.; Demetriadou A.; Narang P. Challenges in Plasmonic Catalysis. ACS Nano 2020, 14 (12), 16202–16219. 10.1021/acsnano.0c08773. PubMed DOI

Zhou X.; Gossage Z. T.; Simpson B. H.; Hui J.; Barton Z. J.; Rodríguez-López J. Electrochemical Imaging of Photoanodic Water Oxidation Enhancements on TiO2 Thin Films Modified by Subsurface Aluminum Nanodimers. ACS Nano 2016, 10 (10), 9346–9352. 10.1021/acsnano.6b04004. PubMed DOI

Yu Y.; Sundaresan V.; Willets K. A. Hot Carriers versus Thermal Effects: Resolving the Enhancement Mechanisms for Plasmon-Mediated Photoelectrochemical Reactions. J. Phys. Chem. C 2018, 122 (9), 5040–5048. 10.1021/acs.jpcc.7b12080. DOI

Schorr N. B.; Counihan M. J.; Bhargava R.; Rodríguez-López J. Impact of Plasmonic Photothermal Effects on the Reactivity of Au Nanoparticle Modified Graphene Electrodes Visualized Using Scanning Electrochemical Microscopy. Anal. Chem. 2020, 92 (5), 3666–3673. 10.1021/acs.analchem.9b04754. PubMed DOI

Yu Y.; Wijesekara K. D.; Xi X.; Willets K. A. Quantifying Wavelength-Dependent Plasmonic Hot Carrier Energy Distributions at Metal/Semiconductor Interfaces. ACS Nano 2019, 13 (3), 3629–3637. 10.1021/acsnano.9b00219. PubMed DOI

Henrotte O.; Santiago E. Y.; Movsesyan A.; Mascaretti L.; Afshar M.; Minguzzi A.; Vertova A.; Wang Z. M.; Zboril R.; Kment S.; Govorov A. O.; Naldoni A. Local Photochemical Nanoscopy of Hot-Carrier-Driven Catalytic Reactions Using Plasmonic Nanosystems. ACS Nano 2023, 17 (12), 11427–11438. 10.1021/acsnano.3c01009. PubMed DOI

Kiani F.; Bowman A. R.; Sabzehparvar M.; Karaman C. O.; Sundararaman R.; Tagliabue G. Transport and Interfacial Injection of D-Band Hot Holes Control Plasmonic Chemistry. ACS Energy Lett. 2023, 8, 4242–4250. 10.1021/acsenergylett.3c01505. PubMed DOI PMC

Henrotte O.; Kment Š.; Naldoni A. Interfacial States in Au/Reduced TiO2 Plasmonic Photocatalysts Quench Hot-Carrier Photoactivity. J. Phys. Chem. C 2023, 127 (32), 15861–15870. 10.1021/acs.jpcc.3c04176. PubMed DOI PMC

Bard A. J.; Fan F. R. F.; Kwak J.; Lev O. SCANNING ELECTROCHEMICAL MICROSCOPY - INTRODUCTION AND PRINCIPLES. Anal. Chem. 1989, 61 (2), 132–138. 10.1021/ac00177a011. DOI

Sun P.; Mirkin M. V. Electrochemistry of Individual Molecules in Zeptoliter Volumes. J. Am. Chem. Soc. 2008, 130 (26), 8241–8250. 10.1021/ja711088j. PubMed DOI

Yu Y.; Sun T.; Mirkin M. V. Scanning Electrochemical Microscopy of Single Spherical Nanoparticles: Theory and Particle Size Evaluation. Anal. Chem. 2015, 87 (14), 7446–7453. 10.1021/acs.analchem.5b01690. PubMed DOI

Kwak J.; Bard A. J. Scanning Electrochemical Microscopy. Theory of the Feedback Mode. Anal. Chem. 1989, 61 (11), 1221–1227. 10.1021/ac00186a009. DOI

Amphlett J. L.; Denuault G. Scanning Electrochemical Microscopy (SECM): An Investigation of the Effects of Tip Geometry on Amperometric Tip Response. J. Phys. Chem. B 1998, 102 (49), 9946–9951. 10.1021/jp982829u. DOI

Eloul S.; Compton R. G. General Model of Hindered Diffusion. J. Phys. Chem. Lett. 2016, 7 (21), 4317–4321. 10.1021/acs.jpclett.6b02275. PubMed DOI

Rodríguez O.; Denuault G. The Influence of the Oxygen Reduction Reaction (ORR) on Pt Oxide Electrochemistry. ChemElectroChem. 2021, 8 (18), 3525–3532. 10.1002/celc.202100710. DOI

Eckhard K.; Chen X.; Turcu F.; Schuhmann W. Redox Competition Mode of Scanning Electrochemical Microscopy (RC-SECM) for Visualisation of Local Catalytic Activity. Phys. Chem. Chem. Phys. 2006, 8 (45), 5359–5365. 10.1039/b609511a. PubMed DOI

Henrotte O.; Boudet A.; Limani N.; Bergonzo P.; Zribi B.; Scorsone E.; Jousselme B.; Cornut R. Steady-State Electrocatalytic Activity Evaluation with the Redox Competition Mode of Scanning Electrochemical Microscopy: A Gold Probe and a Boron-Doped Diamond Substrate. ChemElectroChem. 2020, 7, 4633–4640. 10.1002/celc.202001088. DOI

Martin R. D.; Unwin P. R. Theory and Experiment for the Substrate Generation Tip Collection Mode of the Scanning Electrochemical Microscope: Application as an Approach for Measuring the Diffusion Coefficient Ratio of a Redox Couple. Anal. Chem. 1998, 70 (2), 276–284. 10.1021/ac970681p. DOI

Sánchez-Sánchez C. M.; Rodríguez-López J.; Bard A. J. Scanning Electrochemical Microscopy. 60. Quantitative Calibration of the SECM Substrate Generation/Tip Collection Mode and Its Use for the Study of the Oxygen Reduction Mechanism. Anal. Chem. 2008, 80 (9), 3254–3260. 10.1021/ac702453n. PubMed DOI

El-Sayed M. A. Some Interesting Properties of Metals Confined in Time and Nanometer Space of Different Shapes. Acc. Chem. Res. 2001, 34 (4), 257–264. 10.1021/ar960016n. PubMed DOI

Kang M.; Park S.-G.; Jeong K.-H. Repeated Solid-State Dewetting of Thin Gold Films for Nanogap-Rich Plasmonic Nanoislands. Sci. Rep. 2015, 5 (1), 14790.10.1038/srep14790. PubMed DOI PMC

Cornut R.; Lefrou C. A Unified New Analytical Approximation for Negative Feedback Currents with a Microdisk SECM Tip. J. Electroanal. Chem. 2007, 608 (1), 59–66. 10.1016/j.jelechem.2007.05.007. DOI

Scanlon D. O.; Dunnill C. W.; Buckeridge J.; Shevlin S. A.; Logsdail A. J.; Woodley S. M.; Catlow C. R. A.; Powell M. J.; Palgrave R. G.; Parkin I. P.; Watson G. W.; Keal T. W.; Sherwood P.; Walsh A.; Sokol A. A. Band Alignment of Rutile and Anatase TiO2. Nat. Mater. 2013, 12 (9), 798–801. 10.1038/nmat3697. PubMed DOI

Santiago E. Y.; Besteiro L. V.; Kong X.; Correa-duarte M. A.; Wang Z.; Govorov A. O. Efficiency of Hot-Electron Generation in Plasmonic Nanocrystals with Complex Shapes: Surface-Induced Scattering, Hot Spots, and Interband Transitions. ACS Photonics 2020, 7, 2807–2824. 10.1021/acsphotonics.0c01065. DOI

Brown A. M.; Sundararaman R.; Narang P.; Goddard W. A.; Atwater H. A. Nonradiative Plasmon Decay and Hot Carrier Dynamics: Effects of Phonons, Surfaces, and Geometry. ACS Nano 2016, 10, 957–966. 10.1021/acsnano.5b06199. PubMed DOI

Khurgin J. B. Fundamental Limits of Hot Carrier Injection from Metal in Nanoplasmonics. Nanophotonics 2020, 9 (2), 453–471. 10.1515/nanoph-2019-0396. DOI

Oleinick A. I.; Battistel D.; Daniele S.; Svir I.; Amatore C. Simple and Clear Evidence for Positive Feedback Limitation by Bipolar Behavior during Scanning Electrochemical Microscopy of Unbiased Conductors. Anal. Chem. 2011, 83 (12), 4887–4893. 10.1021/ac2006075. PubMed DOI

Mao Z.; Vang H.; Garcia A.; Tohti A.; Stokes B. J.; Nguyen S. C. Carrier Diffusion—The Main Contribution to Size-Dependent Photocatalytic Activity of Colloidal Gold Nanoparticles. ACS Catal. 2019, 9 (5), 4211–4217. 10.1021/acscatal.9b00390. DOI

Jain P. K.; Lee K. S.; El-Sayed I. H.; El-Sayed M. A. Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine. J. Phys. Chem. B 2006, 110 (14), 7238–7248. 10.1021/jp057170o. PubMed DOI