scholarly journals Hot Electrons in TiO2–Noble Metal Nano-Heterojunctions: Fundamental Science and Applications in Photocatalysis

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1249
Author(s):  
Ajay P. Manuel ◽  
Karthik Shankar
Keyword(s):  
Noble Metal ◽  
Focal Point ◽  
Solar Spectrum ◽  
Metal Nanoparticle ◽  
Hot Electrons ◽  
Localized Surface Plasmon ◽  
Quantum Yields ◽  
Hot Electron ◽  
Interband Transitions ◽  
Metal Metal

Plasmonic photocatalysis enables innovation by harnessing photonic energy across a broad swathe of the solar spectrum to drive chemical reactions. This review provides a comprehensive summary of the latest developments and issues for advanced research in plasmonic hot electron driven photocatalytic technologies focusing on TiO2–noble metal nanoparticle heterojunctions. In-depth discussions on fundamental hot electron phenomena in plasmonic photocatalysis is the focal point of this review. We summarize hot electron dynamics, elaborate on techniques to probe and measure said phenomena, and provide perspective on potential applications—photocatalytic degradation of organic pollutants, CO2 photoreduction, and photoelectrochemical water splitting—that benefit from this technology. A contentious and hitherto unexplained phenomenon is the wavelength dependence of plasmonic photocatalysis. Many published reports on noble metal-metal oxide nanostructures show action spectra where quantum yields closely follow the absorption corresponding to higher energy interband transitions, while an equal number also show quantum efficiencies that follow the optical response corresponding to the localized surface plasmon resonance (LSPR). We have provided a working hypothesis for the first time to reconcile these contradictory results and explain why photocatalytic action in certain plasmonic systems is mediated by interband transitions and in others by hot electrons produced by the decay of particle plasmons.

scholarly journals Mechanistic insight into deep holes from interband transitions in Palladium nanoparticle photocatalysts

2021 ◽  
Author(s):  
Pin Lyu ◽  
Randy Espinoza ◽  
Md. Imran Khan ◽  
William C. Spaller ◽  
Sayantani Ghosh ◽  
...  
Keyword(s):  
Metallic Nanoparticles ◽  
Aryl Halide ◽  
Localized Surface Plasmon ◽  
Quantum Yields ◽  
Mechanistic Study ◽  
Hot Electron ◽  
Interband Transitions ◽  
Electron Transfer Mechanism ◽  
Pd Nanoparticle

Photocatalysis of metallic nanoparticles, especially utilizing hot electrons generated from localized surface plasmon resonance, is of widespread interest. However, the role of hot holes, especially generated from interband transitions, has not been emphasized in exploring the photocatalytic mechanism yet. In this study, a photocatalyzed Suzuki-Miyaura reaction using mesoporous Pd nanoparticle photocatalyst served as a model reaction to study the role of hot holes by accurately measuring the quantum yields of the photocatalyst. The quantum yields increase under shorter wavelength excitations and correlate to the “deeper” energy of the holes from the Fermi level. Our mechanistic study suggests that deeper holes in the d-band can catalyze the oxidative addition of aryl halide R-X onto Pd0 at the surface of nanoparticles to form the R-PdII-X complex, the rate-determining step of the established catalytic cycle. We pointed out that this deep hole mechanism should deserve as much attention as the well-known hot electron transfer mechanism in previous studies.

Gold Nanorods Coated Metallic Photonic Crystal for Enhanced Hot Electron Transfer in Electrochemical Cells

MRS Advances ◽  
2015 ◽  
Vol 1 (13) ◽  
pp. 831-837 ◽  
Author(s):  
A. Elfaer ◽  
Y. Wang ◽  
X. H. Li ◽  
J. B. Chou ◽  
S-G. Kim
Keyword(s):  
Electron Transfer ◽  
Gold Nanorods ◽  
Near Infrared ◽  
Fuel Efficiency ◽  
Solar Spectrum ◽  
Localized Surface Plasmon ◽  
Bandgap Energy ◽  
Hot Electron ◽  
Photocurrent Measurement ◽  
Hot Electron Transfer

ABSTRACTWe recently demonstrated a sub-bandgap photoresponse with our wafer-scale Au/TiO2 metallic-semiconductor photonic crystals (MSPhC). The sub-bandgap energy with 590 nm peak could be absorbed in the form of hot electron and injected to TiO2, which provides 5.28 times more energy for photolysis than that of energy absorbed to flat TiO2. If the solar energy already absorbed above 700 nm could be injected to the catalyst, higher than 10 times improvement will be achieved, and above 20% solar to fuel efficiency will be feasible with the robust but inefficient TiO2 catalyst. In order to achieve photocurrent near and above 700 nm spectrum, we deposited gold nanorods on the surface of MSPhC to incur localized surface plasmon (LSP) modes absorption and subsequent injection to the TiO2 catalyst. We used electrophoretic deposition (EPD) method to deposit nanorods on the top, sidewall and bottom well surface of the photonic nanocavities. The deposition of nanorods was achieved reasonably uniform and sparse not to block the optical cavities of MSPhC. Flat gold surfaces were tested at 4 different suspension densities to get the optimum gold nanorods density. Under 10V applied electric field, positively charged gold nanorods at the concentration of 6.52×1013 #/mL could deposit MSPhC surface with the density of 230 #/µm2, which was reasonably uniform and sparse. Preliminary tests show an absorbance increase near 700 nm on flat device coated with gold nanorods. Photocurrent measurement is under way to demonstrate the enhanced hot electron transfer over full visible light and near-infrared solar spectrum.

scholarly journals Understanding Electromagnetic Interactions and Electron Transfer in Ga Nanoparticle–Graphene–Metal Substrate Sandwich Systems

2019 ◽  
Vol 9 (19) ◽  
pp. 4085 ◽  
Author(s):  
Yael Gutiérrez ◽  
Maria M. Giangregorio ◽  
April S. Brown ◽  
Fernando Moreno ◽  
Maria Losurdo
Keyword(s):  
Contact Angle ◽  
Electron Transfer ◽  
Noble Metal ◽  
Metal Substrate ◽  
Metal Nanoparticle ◽  
Localized Surface Plasmon ◽  
Graphene Layers ◽  
Electromagnetic Enhancement ◽  
Electromagnetic Interactions ◽  
Surface Enhanced

Plasmonic metal nanoparticle (NP)–graphene (G) systems are of great interest due their potential role in applications as surface-enhanced spectroscopies, enhanced photodetection, and photocatalysis. Most of these studies have been performed using noble metal NPs of silver and gold. However, recent studies have demonstrated that the noble metal–graphene interaction leads to strong distortions of the graphene sheet. In order to overcome this issue, we propose the use of Ga NPs that, due to their weak interaction with graphene, do not produce any deformation of the graphene layers. Here, we analyze systems consisting of Ga NP/G/metal sandwich coupling structures, with the metal substrate being, specifically, copper (Cu) and nickel (Ni), i.e., Ga NP/G/Cu and Ga NPs/G/Ni. We experimentally show through real-time plasmonic spectroscopic ellipsometry and Raman spectroscopy measurements of the quenching of the Ga NP localized surface plasmon resonance (LSPR) depending on the wetting of the graphene by the Ga NPs and on the electron transfer through graphene. Theoretical finite-difference time-domain (FDTD) simulations supportively demonstrate that the LSPR in such sandwich structures strongly depends on the contact angle of the NP with graphene. Finally, we also provide evidence of the electron transfer from the Ga NPs into the graphene and into the metal substrate according to the work function alignments. These considerations about the contact angle and, consequently, geometry and wetting of the metal NPs on graphene, are useful to guide the design of those plasmonic systems to maximize electromagnetic enhancement.

SERS and RI sensing properties of heterogeneous dimers of Au and Si nanospheres

2021 ◽  
pp. 2150378
Author(s):  
Tian Yi Fu ◽  
Chao Ling Du ◽  
Yang Xi Chen ◽  
Ru Xin Zhang ◽  
Lu Sun ◽  
...  
Keyword(s):  
Noble Metal ◽  
Near Field ◽  
Resonance Energy ◽  
Metal Nanoparticle ◽  
Localized Surface Plasmon ◽  
Sensitivity Factor ◽  
Field Coupling ◽  
Extinction Spectra ◽  
Surface Enhanced Raman ◽  
Potential Applications

Heterogeneous dimers of Au and Si nanoparticles are expected to exhibit different plasmon properties from that of homogeneous noble metal nanoparticle dimers. It is crucial to unveil the potential applications in surface-enhanced Raman scattering (SERS) and refractive-index (RI) sensing of the prototype dimer of Au and Si nanospheres. The near-field coupling between the two components within the dimer is revealed to not affect the resonance energy of Si mode in the extinction spectra, but decrease that of Au mode. It also accounts for the plasmon ruler behavior of the fractional shifts of both its dipolar peak wavelength of localized surface plasmon resonance (LSPR) and corresponding RI sensitivity factor [Formula: see text], which provide another kind of substitute to estimate the gap distance in between components within the dimer as that of noble metal nanoparticle dimers. Additionally, by tracking the inflection point shift of the corresponding extinction spectra, its [Formula: see text] is revealed to improve 36% than that of traditional one. The maximum [Formula: see text] and SERS enhancement factor [Formula: see text] at 2 nm gap distance are demonstrated to reach 336 nm RIU[Formula: see text] and [Formula: see text], respectively. This work paves a new way for developing efficient SERS and RI sensing substrates by combining noble metal and dielectric nanoparticles.

scholarly journals Hot-Electron Intraband Luminescence from Single Hot Spots in Noble-Metal Nanoparticle Films

2015 ◽  
Vol 115 (6) ◽  
Author(s):  
Tobias Haug ◽  
Philippe Klemm ◽  
Sebastian Bange ◽  
John M. Lupton
Keyword(s):  
Noble Metal ◽  
Hot Spots ◽  
Metal Nanoparticle ◽  
Hot Electron ◽  
Nanoparticle Films

scholarly journals Plasmonic hot-electron photodetection with quasi-bound states in the continuum and guided resonances

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenhao Wang ◽  
Lucas V. Besteiro ◽  
Peng Yu ◽  
Feng Lin ◽  
Alexander O. Govorov ◽  
...  
Keyword(s):  
Bound States ◽  
Structural Parameters ◽  
Hybrid Structure ◽  
Fine Tuning ◽  
Hot Electrons ◽  
Hot Electron ◽  
Perfect Absorption ◽  
High Loss ◽  
Guided Mode ◽  
The Continuum

Abstract Hot electrons generated in metallic nanostructures have shown promising perspectives for photodetection. This has prompted efforts to enhance the absorption of photons by metals. However, most strategies require fine-tuning of the geometric parameters to achieve perfect absorption, accompanied by the demanding fabrications. Here, we theoretically propose a Ag grating/TiO2 cladding hybrid structure for hot electron photodetection (HEPD) by combining quasi-bound states in the continuum (BIC) and plasmonic hot electrons. Enabled by quasi-BIC, perfect absorption can be readily achieved and it is robust against the change of several structural parameters due to the topological nature of BIC. Also, we show that the guided mode can be folded into the light cone by introducing a disturbance to become a guided resonance, which then gives rise to a narrow-band HEPD that is difficult to be achieved in the high loss gold plasmonics. Combining the quasi-BIC and the guided resonance, we also realize a multiband HEPD with near-perfect absorption. Our work suggests new routes to enhance the light-harvesting in plasmonic nanosystems.

scholarly journals Current Strategies for Noble Metal Nanoparticle Synthesis

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Giyaullah Habibullah ◽  
Jitka Viktorova ◽  
Tomas Ruml
Keyword(s):  
Noble Metal ◽  
Noble Metals ◽  
Drug Carriers ◽  
Industrial Applications ◽  
Metal Nanoparticle ◽  
Noble Metal Nanoparticles ◽  
Synthesis Methods ◽  
Gold And Silver Nanoparticles ◽  
Diverse Range ◽  
The Past

AbstractNoble metals have played an integral part in human history for centuries; however, their integration with recent advances in nanotechnology and material sciences have provided new research opportunities in both academia and industry, which has resulted in a new array of advanced applications, including medical ones. Noble metal nanoparticles (NMNPs) have been of great importance in the field of biomedicine over the past few decades due to their importance in personalized healthcare and diagnostics. In particular, platinum, gold and silver nanoparticles have achieved the most dominant spot in the list, thanks to a very diverse range of industrial applications, including biomedical ones such as antimicrobial and antiviral agents, diagnostics, drug carriers and imaging probes. In particular, their superior resistance to extreme conditions of corrosion and oxidation is highly appreciated. Notably, in the past two decades there has been a tremendous advancement in the development of new strategies of more cost-effective and robust NMNP synthesis methods that provide materials with highly tunable physicochemical, optical and thermal properties, and biochemical functionalities. As a result, new advanced hybrid NMNPs with polymer, graphene, carbon nanotubes, quantum dots and core–shell systems have been developed with even more enhanced physicochemical characteristics that has led to exceptional diagnostic and therapeutic applications. In this review, we aim to summarize current advances in the synthesis of NMNPs (Au, Ag and Pt).

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