{"id":41,"date":"2017-05-17T04:43:37","date_gmt":"2017-05-17T04:43:37","guid":{"rendered":"http:\/\/wpdev.acsu.buffalo.edu\/watson-research\/?page_id=41"},"modified":"2026-06-10T18:28:53","modified_gmt":"2026-06-10T18:28:53","slug":"research","status":"publish","type":"page","link":"https:\/\/ubwp.buffalo.edu\/watson-research\/research\/","title":{"rendered":"Research"},"content":{"rendered":"

Quantum Dot Heterostructures for Light Harvesting, Excited-State Charge Transfer and Redox Photocatalysis<\/strong><\/h2>\n

We use coordination chemistry, organic chemistry, linker-assisted assembly, and successive ionic layer adsorption and reaction to organize nanoparticles into hybrid materials and heterostructures and to attach light-harvesting chromophores to surfaces of nanoparticles and thin films. Our goal is to assemble materials that undergo excited-state charge transfer \u2013 separating photogenerated electrons from holes and maximizing lifetimes of these charge carriers \u2013 and redox photocatalysis.<\/p>\n

We typically use time-resolved spectroscopy to characterize excited-state interfacial charge-transfer processes and photoelectrochemistry and photochemistry to evaluate photocatalytic performance. A central theme of our research is to understand the influence of interfacial composition and electronic structure on the dynamics and yield of excited-state charge-transfer processes and the mechanism and efficiency of redox photocatalysis. Additional details on several current research projects in our group are as follows.<\/p>\n

Sb2<\/sub>VO5<\/sub>\/CdS-porphyrin Heterostructures: Ultrafast Interfacial Charge Separation Enables the Photocatalytic Reduction of CO<\/strong>2<\/sub><\/strong>\u00a0with 100% Selectivity Relative to the Hydrogen Evolution Reaction<\/strong><\/h3>\n

In collaboration with the research groups of Profs. Sarbajit Banerjee and Tim Cook, we are developing ternary heterostructured photocatalysts. Building on our longstanding collaboration with the Banerjee group (see below), we recently discovered that sub-picosecond hole transfer from photoexcited CdS QDs to Sb2<\/sub>VO5<\/sub> nanorods facilitates the transfer of electrons from CdS to Zn(II) porphyrins to initiate the photocatalytic reduction of CO2<\/sub>. Ternary Sb2<\/sub>VO5<\/sub>\/CdS-porphyrin heterostructures selectively reduce CO2<\/sub>, to CO and CH4<\/sub>, whereas binary Sb2<\/sub>VO5<\/sub>\/CdS heterostructures and CdS-porphyrin dyads promote the reduction of both CO2<\/sub> and protons. Our results reveal that Sb2<\/sub>VO5<\/sub>\/CdS-porphyrin heterostructures are promising CO2<\/sub>-reduction photocatalysts and, more generally, that the light-initiated mechanisms of heterostructures can be tuned with composition and interfacial properties to engender new reactivity and selectivity in photocatalysis.<\/p>\n

\"Mechanisms<\/div>\n

Figure 1: <\/strong>Schematic representation of photocatalytic mechanisms mediated by CdS-porphyrin dyads and ternary Sb2<\/sub>VO5<\/sub>\/CdS-porphyrin heterostructures: The dyads promote both the hydrogen-evolution reaction (HER) and the\u00a0CO2<\/sub>-reduction reaction (CO2<\/sub>RR), whereas the ternary structures are selective for CO2<\/sub>RR.\u00a0 (From Wijethunga et al. J. Am. Chem. Soc. <\/em>2025, <\/strong>147,<\/em> 44834-44844. DOI:10.1021\/jacs.5c12173<\/a>)<\/p>\n

Our first publication on Sb2<\/sub>VO5<\/sub>\/CdS-porphyrin heterostructure<\/u><\/em>s:<\/u><\/em><\/p>\n

Wijethunga, U.K.; Harrell, M.A.; Ayala, J.R.; Giem, A.R.; Garc\u00eda-Pedraza, K.E.; Zhang, D.; Pakhira, A.; Crawley, M.R.; Li, Y.C.; Banerjee, S.; Cook, T.R.; Watson, D.F. \u201cPhotocatalytic CO2<\/sub> Reduction by Ternary Heterostructures of Sb2<\/sub>VO5<\/sub> Nanorods, CdS Quantum Dots, and a Zinc(II) Porphyrin Complex.\u201d J. Am. Chem. Soc.<\/em> 2025,<\/strong> 147,<\/em> 44834-44844.\u00a0DOI:10.1021\/jacs.5c12173<\/a><\/p>\n

Quantum Dot-Mx<\/sub>V2<\/sub>O5<\/sub> Heterostructures: Exploiting Quantum Confinement and Intercalative Mid-Gap States in Interfacial Charge Transfer and Photocatalysis<\/strong><\/h3>\n

As part of a broader collaborative project with Prof. Sarbajit Banerjee’s group, we are fabricating quantum dot (QD)-Mx<\/sub>V2<\/sub>O5<\/sub> heterostructures (where M is a main-group or transition metal cation and x is its stoichiometry) with intriguing electronic and optical properties for light-harvesting, charge transfer, and redox photocatalysis. Mx<\/sub>V2<\/sub>O5<\/sub> materials exhibit intercalative mid-gap electronic states that can accept photogenerated holes from QDs on ultrafast time scales. This charge-separation mechanism enables productive redox chemistry, such as the reduction of protons to hydrogen, to outcompete electron-hole recombination. We have now reported on the synthesis, characterization, excited-state charge-transfer reactivity, and photocatalytic performance of a range of heterostructures in which chalcogenide QDs are interfaced with, for example, Pb0.33<\/sub>V2<\/sub>O5<\/sub>, Sn0.23<\/sub>V2<\/sub>O5<\/sub>, and Sb2<\/sub>VO5<\/sub>\u00a0compounds.<\/p>\n

\n

\"Mechanism<\/p>\n<\/div>\n

Figure 2: <\/strong>Schematic representation of Sb2<\/sub>VO5<\/sub> and the energetic offsets and excited-state charge-transfer mechanisms of Sb2<\/sub>VO5<\/sub>\/CdS heterostructures that lead to photocatalytic hydrogen evolution. (From Zaheer et al.\u00a0Chem Catal. <\/em>2024,\u00a0<\/strong>4,<\/em>\u00a0100844.\u00a0DOI:10.1016\/j.checat.2023.100844<\/a>)<\/p>\n

\"Materials-assembly<\/div>\n

Figure 3: <\/strong>(a) Assembly of QD\/Mx<\/sub>V2<\/sub>O5<\/sub> heterostructures via SILAR and LAA, (b-f) electron microscopy images of various heterostructures, and (g) Raman spectra of CdS\/Pb0.33<\/sub>V2<\/sub>O5<\/sub> heterostructures prepared via SILAR and LAA. (From Handy et al. Chem. Mater.<\/em> 2022, <\/strong>34,<\/em> 1439. DOI:10.1021\/acs.chemmater.1c03762<\/a><\/p>\n

Recent publications on QD\/<\/u><\/em>Mx<\/sub>V2<\/sub>O5<\/sub><\/u><\/em> heterostructures:<\/u><\/em><\/p>\n

    \n
  1. Garc\u00eda-Pedraza, K.E.; Ayala, J.; Wijethunga, U.; Giem, A.R.; Agbeworvi, G.; Banerjee, S.; Watson, D.F. \u201cHeterostructures of Ni(II)-doped CdS Quantum Dots and \u03b2-Pb0.33V2O5 Nanowires: Enhanced Charge Separation and Redox Photocatalysis via Doping of QDs.\u201d Nano Research<\/em> 2024,<\/strong> 17,<\/em> 10279-10291.\u00a0DOI:10.1007\/s12274-024-6675-5<\/a><\/li>\n
  2. Ayala, J.R.; Garc\u00eda-Pedraza, K.E.; Giem, A.R.; Wijethunga, U.; Hariyani, S.; Carrillo, L.; Jaya, C.; Weiland, C.; Fischer, D.A.; Watson, D.F.; Banerjee, S. \u201cInterface-modulated kinetic differentials in electron and hole transfer rates as a key design principle for redox photocatalysis by Sb2VO5\/QD heterostructures.\u201d J. Chem. Phys.<\/em> 2024,<\/strong> 160,<\/em> 194703.\u00a0DOI:10.1063\/5.0201550<\/a><\/li>\n
  3. Zaheer, W.; McGranahan, C. R.; Ayala, J. R.; Garc\u00eda-Pedraza, K.; Carrillo, L. J.; Rothfuss, A. R. M.; Wijethunga, U.; Agbeworvi, G.; Giem, A. R.; Andrews, J. L.; Handy, J. V.; Perez-Beltran, S.; Calderon-Oliver, R; Ma, L.; Ehrlich, S. N.; Jaye, C.; Weiland, C.; Fischer, D. A.; Watson, D. F.; Banerjee, S. \u201cPhotocatalytic Hydrogen Evolution Mechanisms Mediated by Stereoactive Lone Pairs of Sb2<\/sub>VO5<\/sub> in Quantum Dot Heterostructures.\u201d Chem Catalysis<\/em> 2024,<\/strong> 4, <\/em>100844. DOI:10.1016\/j.checat.2023.100844<\/a><\/li>\n
  4. Handy, J. V.; Zaheer, W.; Rothfuss, A. R. M.; McGranahan, C. R.; Agbeworvi, G.; Andrews, J. L.; Garc\u00eda-Pedraza, K. E.; Ponis, J. D.; Ayala, J. R.; Ding, Y.; Watson, D. F.; Banerjee, S. \u201cLone but Not Alone: Precise Positioning of Lone Pairs for the Design of Photocatalytic Architectures.\u201d Chem. Mater. <\/em>2022,<\/strong> 34,<\/em> 1439-1458. DOI:10.1021\/acs.chemmater.1c03762<\/a><\/li>\n
  5. Abdel Razek, S.; Popeil, M. R.; Wangoh, L.; Rana, J.; Suwandaratne, N.; Andrews, J. L.; Watson, D. F.; Banerjee, S.; Piper, L. F. J. \u201cDesigning Catalysts for Water Splitting Based on Electronic Structure Considerations.\u201d Struct.<\/em> 2020,<\/strong> 2, <\/em>023001. DOI:10.1088\/2516-1075\/ab7d86<\/a><\/li>\n
  6. Chauhan, S.; Sheng, A.; Cho, J.; Abdel Razek, S.; Suwandaratne, N.; Sfeir, M. Y.; Piper, L. F. J.; Banerjee, S.; Watson, D. F. \u201cType-II Heterostructures of \u03b1-V2<\/sub>O5<\/sub> Nanowires Interfaced with Cadmium Chalcogenide Quantum Dots: Programmable Energetic Offsets, Ultrafast Charge Transfer, and Photocatalytic Hydrogen Evolution.\u201d Chem. Phys. <\/em>2019,<\/strong> 151, <\/em>224702. DOI: 10.1063\/1.5128148<\/a><\/li>\n
  7. Cho, J.; Sheng, A.; Suwandaratne, N.; Wangoh, L.; Andrews, J. L.; Zhang, P.; Piper, L. F. J.; Watson, D. F.; Banerjee, S. \u201cThe Middle Road Less Taken: Electronic-Structure-Inspired Design of Hybrid Photocatalytic Platforms for Solar Fuel Generation.\u201d Chem. Res. <\/em>2019,<\/strong> 52, <\/em>645-655 (cover article<\/em>). DOI:10.1021\/acs.accounts.8b00378<\/a><\/li>\n
  8. Andrews, J. L.; Cho, J.; Wangoh, L.; Suwandaratne, N.; Sheng, A.; Chauhan, S.; Nieto, K.; Mohr, A.; Kadassery, K. J.; Popeil, M. R.; Thakur, P. K.; Sfeir, M. Y.; Lacy, D. C.; Lee, T.-L.; Zhang, P.; Watson, D. F.; Piper, L. F. J.; Banerjee, S. \u201cHole Extraction by Design in Photocatalytic Architectures Interfacing CdSe Quantum Dots with Topochemically Stabilized Tin Vanadium Oxide.\u201d Am. Chem. Soc. <\/em>2018,<\/strong> 140, <\/em>17163-17174 (cover article<\/em><\/strong>). DOI:10.1021\/jacs.8b09924<\/a><\/li>\n<\/ol>\n

    \u00a0<\/strong><\/p>\n

    Quantum Dot-MoS2<\/sub> Heterostructures for Light-Harvesting, Charge Transfer, and Redox Photocatalysis<\/strong><\/h3>\n

    Our collaborative team has recently developed syntheses of QD\/MoS2<\/sub> heterostructures in which chalcogenide QDs are interfaced with MoS2<\/sub> nanosheets via linker-assisted assembly or successive ionic layer adsorption and reaction (SILAR). Photoexcitation of QDs leads to the transfer of electrons to MoS2<\/sub>, and charge transfer can be exploited in the photocatalytic reduction of protons to hydrogen in the absence of a solvated co-catalyst. Charge-transfer dynamics and photocatalytic performance are tunable with properties of the QD\/MoS2<\/sub> interface.<\/p>\n

    \n
    \"Schematic<\/div>\n<\/div>\n
    Figure 4: <\/strong>Schematic representation of ligand-bridged CdS\/MoS2<\/sub> heterostructures and ligand-dependent electron-transfer dynamics.(From Rothfuss, A. R. M. et al. ACS Appl. Mater. Interfaces<\/em> 2023, <\/strong>15, <\/em>39966-39979. DOI:10.1021\/acsami.3c06722)<\/a><\/div>\n
    <\/div>\n
    \n

    Recent publications on QD\/MoS2<\/sub> heterostructures:<\/u><\/em><\/p>\n

      \n
    1. Rothfuss, A. R. M.; Ayala, J. R.; Handy, J. V.; McGranahan, C. R.; Garc\u00eda-Pedraza, K. E.; Banerjee, S.; Watson, D. F. \u201cLinker-Assisted Assembly of Ligand-Bridged CdS\/MoS2<\/sub> Heterostructures: Tunable Light-Harvesting Properties and Ligand-Dependent Control of Charge-Transfer Dynamics and Photocatalytic Hydrogen Evolution.\u201d ACS Appl. Mater. Interfaces<\/em> 2023, <\/strong>15, <\/em>39966-39979. DOI:10.1021\/acsami.3c06722<\/a><\/li>\n
    2. Cho, J.; Suwandaratne, N. S.; Razek, S.; Choi, Y.-H.; Piper, L. F. J.; Watson, D. F.; Banerjee, S. \u201cElucidating the Mechanistic Origins of Photocatalytic Hydrogen Evolution Mediated by MoS2<\/sub>\/CdS Quantum-Dot Heterostructures.\u201d ACS Appl. Mater. Interfaces <\/em>2020, <\/strong>12,<\/em> 43728-73740. DOI:10.1021\/acsami.0c12583<\/a><\/li>\n<\/ol>\n<\/div>\n

      Fabrication of Quantum Dot Heterostructures via Covalent Bonding between Capping Ligands<\/strong><\/h3>\n

      We tether QDs to each other by forming covalent bonds between terminal functional groups of adsorbed capping ligands. To date, we have focused on the N,N\u2019-dicyclohexylcarbodiimide (DCC)-mediated formation of amide bonds between capping groups of CdS and CdSe QDs to yield QD heterostructures with programmable optical and electronic properties. Additional surface-chemistry steps can enable the formation of bilayers of QDs on charge-accepting semiconductor substrates. Our approach offers two advantages over the use of bifunctional ligands to tether QDs to one another. First, DCC-mediated coupling enables the selective attachment of two different QDs to each other to yield exclusively heterostructures without the undesired formation of homostructures of identical QDs. Second, QDs primed for incorporation into heterostructures have no affinity for each other in the absence of DCC, enabling us to trigger the assembly of materials and to control the rate and extent of coupling reactions and the relative numbers of constituent QDs in molecularly-tethered assemblies. Importantly, we have discovered that our amide-bridged CdS\/CdSe QD heterostructures undergo efficient photoinduced inter-QD charge transfer.<\/p>\n

      \n
      \"Mechanisms<\/div>\n<\/div>\n

      Figure 5: <\/strong>Mechanism of DCC-mediated assembly of CdSe\/CdTe QD heterostructures (top) and metal oxide-immobilized heterostructures (bottom). (From McGranahan, C. R. ACS Appl. Mater. Interfaces<\/em> 2021, <\/strong>13, <\/em>30980-30991. DOI:10.1021\/acsami.1c05653)<\/a><\/p>\n

      Recent publications on QD heterostructures and materials assembly<\/u><\/em><\/p>\n

        \n
      1. McGranahan, C. R.; Watson, D. F. \u201cInfluence of Donor-to-acceptor Ratio on Excited-state Electron Transfer within Covalently Tethered CdSe\/CdTe Quantum Dot Colloidal Heterostructures.\u201d J. Chem. Phys.<\/em> 2022, <\/strong>156, <\/em>054706. DOI:10.1063\/5.0078549<\/a><\/li>\n
      2. McGranahan, C. R.; Wolfe II, G. E.; Falca, A.; Watson, D. F. \u201cExcited-State Charge Transfer and Extended Charge Separation within Covalently Tethered Type-II CdSe\/CdTe Quantum Dot Heterostructures: Colloidal and Multilayered Systems.\u201d ACS Appl. Mater. Interfaces<\/em> 2021, <\/strong>13, <\/em>30980-30991. DOI:10.1021\/acsami.1c05653<\/a><\/li>\n<\/ol>\n

         <\/p>\n

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        Quantum Dot Heterostructures for Light Harvesting, Excited-State Charge Transfer and Redox Photocatalysis We use coordination chemistry, organic chemistry, linker-assisted assembly, and successive ionic layer adsorption and reaction to organize nanoparticles … Continue reading Research<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":225,"featured_media":0,"parent":0,"menu_order":2,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-41","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/pages\/41","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/users\/225"}],"replies":[{"embeddable":true,"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/comments?post=41"}],"version-history":[{"count":22,"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/pages\/41\/revisions"}],"predecessor-version":[{"id":639,"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/pages\/41\/revisions\/639"}],"wp:attachment":[{"href":"https:\/\/ubwp.buffalo.edu\/watson-research\/wp-json\/wp\/v2\/media?parent=41"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}