Prashant K Jain

University of Illinois, Urbana-Champaign | UIUC · Department of Chemistry

The realization of common materials transformations in nanocrystalline systems is fostering the development of novel nanostructures and allowing a deep look into the atomistic mechanisms involved. Galvanic corrosion is one such transformation. We studied galvanic replacement within individual metal nanoparticles by using a combination of plasmonic...

Whereas pathways of chemical reactions involving small molecules are well understood, dynamics of reactions in extended solids remain difficult to elucidate. Frequently, kinetic studies on bulk materials provide a picture averaged over multiple domains or grains, smearing out interesting dynamics such as critical nucleation phenomena or sharp phase...

Co-operativity is a remarkable phenomenon mostly seen in biology, where initial reaction events significantly alter the propensity of subsequent reaction events, giving rise to a nonlinear tightly regulated synergistic response. Here we have found unique evidence of atomic level co-operativity in an inorganic material. A thousand-atom nanocrystal (...

A (nano)crystal-clear view: With doped semiconductor nanocrystals, local chemical events can be probed through their perturbation of the carrier density of the nanocrystal. Examples demonstrate that redox processes and ligand chemistry can induce changes in the vacancy density within copper(I) sulfide nanorods, allowing such events to be detected b...

Localized surface plasmon resonances (LSPRs), known for their fascinating optical properties, have thus far been limited to nanostructures of materials with high steady-state charge carrier densities. Here, we show that even a nonequilibrium charge population can support a LSPR mode. Photocharged zinc oxide (ZnO) nanocrystals show an infrared LSPR,...

Lee, Kim, and coworkers have recently claimed ambient temperature and pressure superconductivity in a modified lead apatite material named LK-99. However, the polycrystalline material synthesized has a significant fraction of copper (I) sulfide. Copper (I) sulfide has a known phase transition at 104 degrees C from an ordered low-temperature phase t...

Metal nanoparticles are attracting interest for their light-absorption properties, but such materials are known to dynamically evolve under the action of chemical and physical perturbations, resulting in changes in their structure and composition. Using a transmission electron microscope equipped for optical excitation of the specimen, the structur...

The ability of transmission electron microscopy (TEM) to image a structure ranging from millimetres to Ångströms has made it an indispensable component of the toolkit of modern chemists. TEM has enabled unprecedented understanding of the atomic structures of materials and how structure relates to properties and functions. Recent developments in TEM...

Electroconversion is seeing a resurgence due to its utility for the manufacturing of chemicals and fuels powered by renewable energy. While catalyst design and engineering has been the key strategy for optimizing electroconversions, we have found that light excitation can instead be used to modulate the electrochemical activity in cases where the e...

Hot carriers generated by localized surface plasmon resonance (LSPR) excitation of plasmonic metal nanoparticles are known to enhance electrocatalytic reactions. However, the participation of plasmonically generated carriers in interfacial electrochemical reactions is often limited by fast relaxation of these carriers. Herein, we address this chall...

Nanostructuring has become a powerful tool for tuning the electronic properties of materials and enhancing transport. As an example of relevance to next-generation battery technologies, nanocrystals have shown promise for realizing fast-ion conduction in solids; however, dissipationless ion transport over extended length scales is hindered by lossy...

Ammonia is a promising liquid-phase carrier for the storage, transport, and deployment of carbon-free energy. However, the realization of an ammonia economy is predicated on the availability of green methods for the production of ammonia powered by electricity from renewable sources or by solar energy. Here, we demonstrate the synthesis of ammonium...

Hybrid plasmonic nanostructures are built on plasmonic metalnanostructures surrounded by catalytic metals or metal oxides. Recent studies have shown that hybrid plasmonic nanocatalysts can concurrently utilize thermal energy and photon stimuli and exhibit high catalytic activity, selectivity, and stability that are not attainable in conventional pu...

The chlorination of methane presents a route for the upgrading of natural gas to value-added products. However, due to the low reactivity of methane, existing chlorination processes require the use of elevated temperatures and catalysts. Here, we report a simple process for the chlorination of methane at near-ambient temperatures using minimal reag...

The plasmonic excitations of metal nanostructures have been shown to result in the generation of energetic charge carriers. In this chapter, we discuss how energetic carriers produced by plasmonic excitation of Au nanoparticles can be harvested and utilized for driving multi-electron redox reactions. While such plasmon-driven photoredox chemistry i...

The understanding and rational design of heterogeneous catalysts for complex reactions, such as CO2 reduction, requires knowledge of elementary steps and chemical species prevalent on the catalyst surface under operating conditions. Using in situ nanoscale surface-enhanced Raman scattering, we probe the surface of a Ag nanoparticle during plasmon-e...

Because plasmonic metal nanostructures combine strong light absorption with catalytically active surfaces, they have become platforms for the light-assisted catalysis of chemical reactions. The enhancement of reaction rates by plasmonic excitation has been extensively discussed. This review focuses on a less discussed aspect: the induction of new r...

Quantum phenomena are typically observable at length and time scales smaller than those of our everyday experience, often involving individual particles or excitations. The past few decades have seen a revolution in the ability to structure matter at the nanoscale, and experiments at the single particle level have become commonplace. This has opene...

Quantum phenomena are typically observable at length and time scales smaller than those of our everyday experience, often involving individual particles or excitations. The past few decades have seen a revolution in the ability to structure matter at the nanoscale, and experiments at the single particle level have become commonplace. This has opene...

Superionic conductors are prime candidates for the electrolytes of all-solid-state batteries. Our understanding of the mechanism and performance of superionic conductors is largely based on their idealized lattice structures. But how do defects in the lattice affect ionic structure and transport in these materials? This is a question answered here...

In plasmon‐excitation‐driven photosynthesis on Au nanoparticles, the primary step is the hole‐mediated splitting of water, which supplies protons and electrons for carbon dioxide conversion. This mechanistic insight into a complex, multistep transformation was obtained from measurements of kinetic isotope effects in the reaction (see picture). Abs...

The photoexcitation of plasmonic nanoparticles has been shown to drive multi-step, multi-carrier transformations like the conversion of CO2 to hydrocarbons. But for such plasmon-driven chemistry to be precisely understood and modeled, the critical photo-initiation step in the reaction cascade must be identified. We meet this goal by measuring H/D a...

A range of chemical reactions occurring on the surfaces of metal nanoparticles exhibit enhanced rates under plasmonic excitation. It is not straightforward to distinguish between photochemical and photothermal effect using Arrhenius fitting of the reaction rates alone.

ConspectusPlasmonic nanostructures have garnered widescale scientific interest because of their strong light-matter interactions and the tunability of their absorption across the solar spectrum. At the heart of their superlative interaction with light is the resonant excitation of a collective oscillation of electrons in the nanostructure by the in...

We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual functionality: the Pt component catalyses the electrochemical oxidation of ammonia to liberate hydrogen and the Au component absorbs visible light by the excitation of localized surface plasmon reso...

A photochemical potential generated by the excitation of localized surface plasmon resonances of a bimetallic Au@Pt nanoparticle catalyst boosts electrochemical ammonia oxidation activity. Abstract We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual...

New advances in label-free optical imaging methods are allowing a wide range of chemical processes in surface science, catalysis, and photochemistry to be probed on the nanoscale and single-molecule levels.

Spin-filtered surface conduction channels set topological insulator (TI) materials apart as a distinct class and grant them physical properties that are suited to discovery of new quantum phenomena and advanced applications such as topological quantum computing. Even though high-throughput band structure investigations have uncovered new TI materia...

Using plasmonically generated carriers as redox equivalents - Volume 45 Issue 1 - Sungju Yu, Varun Mohan, Prashant K. Jain

Noble metals are prime candidates for electrocatalysts for electrochemical energy conversions. In a separate realm, nanostructured noble metals are being found to exhibit photocatalytic activity under plasmonic excitation with no electrical bias. Here, we explore the convergence of the electrocatalytic and photocatalytic activity of nanostructured...

By the photoexcitation of localized surface plasmon resonances of metal nanoparticles, one can generate reaction equivalents for driving redox reactions. We show that, in such cases, there is a chemical potential contributed by the plasmonic excitation. This chemical potential is a function of the concentration of light, as we determine from the li...

By the photoexcitation of localized surface plasmon resonances of metal nanoparticles, one can generate reaction equivalents for driving redox reactions. We show that, in such cases, there is a chemical potential contributed by the plasmonic excitation. This chemical potential is a function of the concentration of light, as we determine from the li...

Several chemical reactions catalyzed by plasmonic nanoparticles show enhanced rates under visible-light-excitation of the localized surface plasmon resonance of the nanoparticles. But it has been argued that there is an associated photothermal effect that can complicate the analysis and/or interpretation of the nature of the role played by plasmon...

The photochemical conversion of CO 2 into fuels has promise as a strategy for storage of intermittent solar energy in the form of chemical bonds. However, higher-energy-value hydrocarbons are rarely produced by this strategy, because of the kinetic challenges associated with multi-electron, multi-proton, and C–C coupling reactions required for hydr...

Electrocatalytic and photocatalytic carbon fixation suffer from a major challenge: the undesirable hydrogen evolution reaction (HER) typically outcompetes the CO2 reduction reaction (CO2RR) amounting to a loss of energetic charge carriers and a reduced selectivity for hydrocarbon production. Likewise, hydrocarbon production by CO2RR and HER also co...

Several chemical reactions catalyzed by plasmonic nanoparticles show enhanced rates under visible-light-excitation of the localized surface plasmon resonance of the nanoparticles. But it has been argued that there is an associated photothermal effect that can complicate the analysis and/or interpretation of the nature of the role played by plasmon...

A range of chemical reactions occurring on the surfaces of metal nanoparticles exhibit enhanced rates under plasmonic excitation. Recent analyses based on Arrhenius law fitting have argued in favor of a purely photothermal mechanism of enhancement and suggested the lack of an involvement of hot electrons. However, there is a caveat as shown here: u...

The engineering of nanoscale features enables the properties of solid-state materials to be tuned. Here, we show the tunable preparation of cuprous sulfide nanocrystals ranging in internal structures from single-domain to multi-domain. The synthetic method utilizes in-situ oxidation to grow nanocrystals with a controlled degree of copper deficiency...

Understanding of the thermodynamic properties of elementary chemical steps of a reaction is important for the development of fundamental reaction theories and for effective industrial practice. In this work, temperature-variable single molecule fluorescence microscopy was employed to study a reversible redox chemical process and reveal the thermody...

Photochemical conversion of CO2 into fuels has promise as a strategy for storage of intermittent solar energy in the form of chemical bonds. However, higher-energy-value hydrocarbons are rarely produced by this strategy, because of kinetic challenges. Here we demonstrate a strategy for green-light-driven synthesis of C1–C3 hydrocarbons from CO2 and...

Multi-electron redox reactions are known to be kinetically sluggish and there has been an ongoing search for synthetic catalysts for such reactions. In recent work from my laboratory, plasmonic nanoparticles have been found to photocatalyze multi-electron processes such as CO 2 reduction and the condensation of ethylene to graphene. However, there...

To mimic natural photosynthesis, one requires a synthetic photocatalyst that can absorb sunlight and direct that energy to the conversion of CO 2 into energy-dense hydrocarbons. My talk will make the case that plasmonic metal nanostructures may be well-suited to this task. With Au, Ag, and Cu nanostructures, it is possible to pair strong light-matt...

Localized surface plasmon resonance (LSPR) excitation of noble metal nanoparticles has been shown to accelerate and drive photochemical reactions. Here, LSPR excitation is shown to enhance the electrocatalysis of a fuel cell‐relevant reaction. The electrocatalyst consists of PdxAg alloy nanotubes (NTs), which combine the catalytic activity of Pd to...

Localized surface plasmon resonance (LSPR) excitation of noble metal nanoparticles has been shown to accelerate and drive photochemical reactions. Here, LSPR excitation is shown to enhance the electrocatalysis of a fuel cell‐relevant reaction. The electrocatalyst consists of PdxAg alloy nanotubes (NTs), which combine the catalytic activity of Pd to...

Cuprous selenide nanocrystals have hallmark attributes, especially tunable localized surface plasmon resonances (LSPRs) and super‐ionic behavior. Here, we integrate these attributes of cuprous selenide with a one‐dimensional morphology. Essentially, Cu2Se nanowires (NWs) of micron‐scale lengths and ca. 10 nm diameters are prepared. The NWs exhibit...

Solid-solid phase transitions are processes ripe for the discovery of correlated atomic motion in crystals. Here, we monitor an order-disorder transition in real-time in nanoparticles of the super-ionic solid, Cu2−xSe. The use of in-situ high-resolution transmission electron microscopy allows the spatiotemporal evolution of the phase transition wit...

Cuprous selenide nanocrystals have hallmark attributes, especially tunable localized surface plasmon resonances (LSPRs) and super‐ionic behavior. Here, we integrate these attributes of cuprous selenide with a one‐dimensional morphology. Essentially, Cu2Se nanowires (NWs) of micron‐scale lengths and ca. 10 nm diameters are prepared. The NWs exhibit...

Long-range order imparts both complexity and diversity to crystalline solid materials, resulting in novel crystal phases and new physical properties. We report the finding of an unconventional long-range ordering of copper ions (Cu⁺) in Cu2-xSe, a well-known ion conductor. High-resolution electron microscopy of Cu2-xSe nanocrystals (NCs) reveals at...

ZnO has industrial utility as a solid sorbent for the removal of polluting sulfur compounds from petroleum-based fuels. Small ZnO nanoparticles may be more effective in terms of sorption capacity and ease of sulfidation as compared to bulk ZnO. Motivated by this promise, here, we study the sulfidation of ZnO NPs and uncover the solid-state mechanis...

Photocatalytic reduction of carbon dioxide (CO2) by visible light has the potential to mimic plant photosynthesis and facilitate the renewable production of storable fuels. Accomplishing desirable efficiency and selectivity in artificial photosynthesis requires understanding of light-driven pathways on photocatalyst surfaces. Here, we probe with si...

Ethylene epoxidation is used to produce 2 × 107 ton per year of ethylene oxide, a major feedstock for commodity chemicals and plastics. While high pressures and temperatures are required for the reaction, plasmonic photoexcitation of the Ag catalyst enables epoxidation at near-ambient conditions. Here, we use surface-enhanced Raman scattering to mo...

Multi-electron redox reactions, although central to artificial photosynthesis, are kinetically sluggish. Amidst the search for synthetic catalysts for such processes, plasmonic nanoparticles have been found to catalyse multi-electron reduction of CO2 under visible light. This example motivates the need for a general, insight-driven framework for pl...

Conversion of solar energy into liquid fuel often relies on multi-electron redox processes that include highly reactive intermediates, with back reaction routes that hinder the overall efficiency of the process. Here we reveal that these undesirable reaction pathways can be minimized, rendering the photocatalytic reactions more efficient, when char...

The search for ion‐conductive solid electrolytes for Li+ batteries is an important scientific and technological challenge with economic and sustainable energy implications. In this study, nanocrystals (NCs) of the ion conductor copper selenide (Cu2Se) were doped with Li by the process of cation exchange. Li2xCu2‐2xSe alloy NCs were formed at interm...

The search for ion‐conductive solid electrolytes for Li+ batteries is an important scientific and technological challenge with economic and sustainable energy implications. In this study, nanocrystals (NCs) of the ion conductor copper selenide (Cu2Se) were doped with Li by the process of cation exchange. Li2xCu2‐2xSe alloy NCs were formed at interm...

Oxygenic photosynthesis in nature occurs via water splitting catalyzed by the oxygen evolving complex (OEC) of photo-system II. To split water, the OEC cycles through a sequence of oxidation states (Si, i = 0-4), the structural mechanism of which is not fully understood under physiological conditions. We monitored the OEC in visible light-driven wa...

An optically modulated scanning tunneling microscopy technique developed for measurement of single-molecule optical absorption is used here to image the light absorption by individual Au nanoislands and Au nanostructures. The technique is shown to spatially map, with nanometer resolution, localized surface plasmons (LSPs) excited within the nanoisl...

Superionic (SI) phases have utility as solid electrolytes for next generation battery technology, but these phases are typically not stable at room temperature. Our density functional theory calculations demonstrate that compressive lattice strain can stabilize SI phases of Cu2Se and Li2Se, two potential solid electrolytes. Electronic and bonding i...

Artificial photosynthesis relies on the availability of synthetic photocatalysts that can drive CO2 reduction in the presence of water and light. From the stand-point of solar fuel production, it is desirable that these photocatalysts perform under visible light and produce energy-rich hydrocarbons from CO2 reduction. However, the multi-step nature...

Lithium-ion (Li-ion) batteries have been dominating the global market for consumer electronics and power vehicles. However, significant safety concerns arise from degradation reactions (reduction/decomposition) of the electrolyte during cycling, potentially causing dendrite formation resulting in leakage and fires. A potential solution is the repla...

The ability of plasmonic nanoparticles to harness visible light can be being combined with their catalytic activity to drive photocatalytic transformations. This Perspective introduces the promise of this new class of photocatalysts for fulfilling the quest for sunlight-driven recycling of CO2 into transportable liquid fuels. We discuss the prospec...

Solution-processed films of methylammonium lead bromide (MAPbBr3) perovskites have remarkable photoluminescence (PL), with utility in light emitting devices (LEDs) and photodiodes; however, the PL emission is often complex, heterogeneous, anomalous, or poorly understood. We provide a deeper understanding by studying PL spectra of single MAPbBr3 cry...

This article demonstrates the power of topotactic synthesis coupled with density functional theory (DFT) for accessing and exploring new phases of matter. Naturally occurring HgSe is a semimetal with a zero gap. Unlike this natural zincblende form of HgSe, our DFT investigations predict that wurtzite HgSe has both an inverted band structure and a b...

The formation of bimetallic nanostructures through the process of galvanic exchange of metal nanoparticle (NP) templates involves a drastic phase transformation with a complex atomistic mechanism. We measured using single-NP plasmonic spectroscopy the true kinetics of galvanic corrosion of Ag by Au3+ salts. An individual Ag NP undergoes an abrupt t...

This work provides mechanistic understanding of hot electron-based catalysis on Au nanoparticles (NPs) induced under plas-monic excitation. Plasmon excitation-induced hot electron transfer from an Au NP (donor) to a ferricyanide anion (acceptor) was stud-ied as a function of the donor-acceptor distance set by a thiolate-based self-assembled monolay...

Super-ionic solids, which exhibit ion mobilities as high as those in liquids or molten salts, have been employed as solid-state electrolytes in batteries, improved thermoelectrics and fast-ion conductors in super-capacitors and fuel cells. Fast-ion transport in many of these solids is supported by a disordered, ‘liquid-like’ sub-lattice of cations...

Supplementary Figures and Supplementary References.

Ultrasmall semiconductor clusters are an exciting class of materials due to their molecularly precise structures and their unique optical spectra. “Magic-sized” CdSe clusters are transformed to their Cu2Se counterparts by means of ion exchange. We leverage the molecularly precise structure and high sensitivity of these clusters to investigate the m...

Anisotropic plasmonic nanostructures are known to exhibit large enhancements of surface-enhanced Raman scattering (SERS) of adsorbed molecules at their sharp tips or edges, where the near-field is intense. We show that the SERS enhancement at such field hotspots decays over a distance of ca. 4 Å, much shorter than the typical decay length reported...

Self-assembled monolayer (SAM) formation of alkanethiols on nanoparticle surfaces is an extensively studied surface reaction. But the nanoscale aspects of the rich microscopic kinetics of this reaction may remain hidden due to ensemble-averaging in colloidal samples, which is why we investigated in real-time how alkanethiol SAMs form on a single Ag...

Bimetallic nanostructures (NSs), with utility in catalysis, are typically prepared using galvanic exchange (GE), but the final catalyst morphology is dictated by the dynamics of the process. In situ single nanoparticle (NP) optical scattering spectroscopy, coupled with ex situ electron microscopy, is used to capture the dynamic structural evolution...

Plasmonic nanorattles comprised of solid plasmonic core and porous and hollow plasmonic shell are a novel class of nanostructures that are highly attractive for surface enhanced Raman scattering (SERS)-based chemical and biological sensing and bioimaging. In this report, we demonstrate the polarization-dependent SERS activity of cuboidal plasmonic...

Bimetallic nanostructures (NSs), with utility in catalysis, are typically prepared using galvanic exchange (GE), but the final catalyst morphology is dictated by the dynamics of the process. In situ single nanoparticle (NP) optical scattering spectroscopy, coupled with ex situ electron microscopy, is used to capture the dynamic structural evolution...

Transition metal nanoparticles, including those employed in catalytic, electrocatalytic, and photocatalytic conversions, have surfaces that are typically coated with a layer of short or long-chain ligands. There is little systematic understanding of how much this ligand layer affects the reactivity of the underlying surface. We show for Ag nanopart...