Noble metal nanoparticles due to their unique optical properties arising from their interactions with an incident light have been intensively employed in a broad range of applications. This review ...comprehensively describes fundamentals behind plasmonics, used to develop applications in the fields of biomedical, energy, and information technologies. Basic concepts (electromagnetic interaction and permittivity of metals) are discussed through Mie theory presented as the main model for interpreting phenomena of optical absorption and scattering. The effects of near‐field enhancement, shape, composition, and surrounding medium of nanoparticles on optical properties are described in detail. The review explores and identifies the potential of plasmonic nanoparticles based on their optical properties (e.g., light absorption, scattering, and field enhancement) for developing different applications (biomedical, energy and information technologies). Due to a significant impact of plasmonic nanoparticles on medicine and healthcare products and technologies, the review initially focuses on biomedical applications extensively benefited from optical features of these nanoparticles. Advantages of the optical properties outstandingly implemented are also briefly discussed in other applications, including energy and information technologies. This review concisely summarizes the explored areas based on plasmonic properties, compares advantages of plasmonic nanoparticles over other types of nanomaterials and highlights challenges.
Plasmonic‐metal nanoparticles, on account of their extraordinary optical properties, are widely applied in various fields based on the absorption, scattering, and near field enhancement effects. The fundamental mechanisms and application‐oriented plasmonic properties of plasmonic‐metal nanoparticles are comprehensively discussed and examined to illustrate their potential for developing cutting‐edge biomedical, energy, and information technologies.
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•Engineering and synthesis strategies of MOF-PMPs in chemical sensing are summarized.•Advances of MOF-PMPs based SERS platforms in food safety are firstly reviewed.•Challenges, ...opportunities and future perspectives of MOF-PMPs are presented.
Enhanced platform is a key in surface-enhanced Raman scattering (SERS) analysis. Metal-organic frameworks (MOFs) are new porous crystalline materials with large specific surface area, adjustable pore structure and facile functionalization. MOFs combining with plasmonic metal particles (PMPs) as ideal SERS platforms (MOF-PMPs) gradually attract more attentions of researchers in sensing fileds. However, few reviews have focused on this fascinating platform applied in monitoring food contaminants up to now. Thus, it is necessary to give a critical summary on advance of MOF-PMPs based SERS platforms in the field of food safety. This review systematically summarized structure engineering and synthesis strategies of MOF-PMPs-based SERS platforms in chemical sensing, and the corresponding advantages and limitations were certainly discussed. Attentions were mainly focused on the practical application of these platforms in food contaminants monitoring. Challenges and opportunities of MOF-PMPs based SERS substrates were deeply analyzed. Also, this review gives opinions and key points of constructing MOF-PMPs based SERS sensing platforms applied in complex food matrix in the future.
Surface-enhanced Raman spectroscopy (SERS) has been identified as a fundamental surface-sensitive technique that boosts Raman scattering by adsorbing target molecules on specific surfaces. The ...application of SERS highly relies on the development of smart SERS substrates, and thus the fabrication of SERS substrates has been constantly improved. Herein, we investigate the impacts of different substrates on SERS technology including plasmonic metal nanoparticles, semiconductors, and hybrid systems in quantitative food safety and quality analysis. We first discuss the fundamentals, substrate designs, and applications of SERS. We then provide a critical review of the recent progress of SERS in its usage for screening and detecting chemical and biological contaminants including fungicides, herbicides, insecticides, hazardous colorants, and biohazards in food samples to assess the analytical capabilities of this technology. Finally, we investigate the future trends and provide practical techniques that could be used to fulfill the requirements for rapid analysis of food at a low cost.
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•Piezoelectricity of UTCN was confirmed by the PFM method;•Ag NPs were anchored on the UTCN by using a thermal decomposition method;•Ag/UTCN exhibits the significantly enhanced ...photocatalytic redox activity;•Enhanced photocatalytic activity is attributed to the synergy of LSPR and piezoelectric effects.
Although plasmonic metal can provide energetic hot electrons by localized surface plasmon resonance (LSPR) effect in plasmonic metal/semiconductor systems during photocatalysis, the high Schottky barrier limits the electron migration at the interface, which is a scientific problem to be solved urgently. Herein, we employed the cooperative piezoelectric field in the plasmonic metal/semiconductor composite system to provide the strain, which can generate a polarized charge that attracts free electrons at the interface, thus moving the band edge down and facilitating the interfacial transfer of the electrons. As a demonstration case of this idea, Ag nanoparticles/ultrathin g-C3N4 nanosheets (Ag/UTCN) were constructed for realizing the synergistic plasmonic and piezoelectric effect, exhibiting the significantly enhanced photocatalytic activity, and the optimal photocatalytic TC degradation rate reached 93.7% and H2 production rate reached 2615 μmol h−1 g−1, respectively. Results of photochemical analysis illustrated that the semiconductor (in the case of UTCN nanosheets) with piezoelectric properties is employed to couple the plasmonic metal (in the case of Ag nanoparticles), which can enable more hot electron injection into the conduction band of the semiconductor to achieve effective carrier separation. This strategy provides a feasible solution for enhancing the efficiency of the photocatalytic system through the synergy of multiple fields.
The massive consumption of fossil energy leads to excessive emissions of CO2, which has caused global warming. Solar-driven CO2 conversion is a promising avenue that could solve the energy crisis and ...environmental pollution issues simultaneously. For photocatalytic CO2 conversion reactions, several photocatalysts have been developed such as semiconductors and plasmonic metal-based catalysts. Among them, plasmonic metal-based catalysts have attracted extensive attention due to their strong light harvesting capacities and low electron–hole pair recombination rates, which are beneficial for photocatalytic CO2 conversion. This review summarizes the progress of plasmonic metal-based catalysts in CO2 reduction with H2, CH4, H2O, and organic chemicals and generalizes the mechanism of plasmonic metal-based catalysts in CO2 conversion reactions.
There is little research on the visible light photocatalytic properties of the hybrids of plasmonic metals and organic molecules (OM) with the HOMO-LUMO gap in the visible range. Here, we investigate ...the mechanism of the visible light enhanced reduction of p-nitrophenol (PNP) by glycerol (a green reductant) at ambient temperature over curcumin functionalized Ag nanoparticles (c-AgNPs). The catalytic activity got significantly boosted under visible light irradiation. Reaction kinetics indicated that the catalytic mechanism followed under visible light and in the dark were different. DFT calculations showed that in the ground state, the HOMO resides on Ag while the LUMO is on the curcumin part of the composite. TD-DFT calculations demonstrated the transfer of charge from Ag to curcumin on photo-excitation. Based on this information, we propose a mechanism for understanding the role of curcumin in this photocatalytic phenomenon.
Schematic representation of the proposed mechanism for explaining photo-reduction of PNP by using glycerol as a green reducing agent over curcumin functionalized Ag nanocatalysts. Display omitted
•Nano-hybrids of plasmonic Ag and curcumin•Plasmonic photocatalysis of p-nitrophenol reduction by glycerol•DFT calculations for the photo-excitation mechanism
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•Cu, Ag, and Au NPs were loaded onto Mg-Al LDH with varying sizes Au > Ag > Cu.•Influence of plasmonic metals over physicochemical properties was investigated.•Au loaded LDH ...composites exhibited the highest degradation of tetracycline.•Schottky junction and the SPR effect were responsible for improved photoactivity.
This work focused on the enhancement of the photocatalytic activity of solvothermal synthesized Mg0.667 Al0.333 (OH)2 (CO3)0.167 (H2O)0.5 layered double hydroxide (LDH) by plasmonic metal (Cu, Ag, and Au) photodeposition (1-3 wt%). HRTEM analysis confirmed the successful loading of plasmonic nanoparticles with varying sizes (Au (∼4–25 nm) > Ag (∼3–12 nm) > Cu (∼2–7 nm)) on the surface of LDH. The effect of different plasmonic metals and their size on the surface structural, optical, electrokinetic, and photocatalytic properties of LDH was investigated. The prepared catalysts were evaluated for the degradation of tetracycline under LED irradiation for 140 min and the photoactivity trend followed the order: pristine LDH < Cu@LDH < Ag@LDH < Au@LDH. The LC-MS studies revealed that the degradation occurred by the attack of various reactive species (O2.-, h+, OḢ) via four paths mainly including hydroxylation, functional group cleavage, and ring-opening reaction. A possible mechanism was proposed for the appreciable enhancement in performance caused by the formation of Schottky barriers and surface plasmon resonance of plasmonic nanoparticles. The results of total organic carbon (TOC) indicated the acceptable mineralization of about 84 %. Less than a 10 % fall in degradation efficiency was observed within four recycle runs.
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•Stacked Au/TiO2/rGO photocatalyst with TiO2 sandwiched between rGO and Au was fabricated.•rGO substrate lowers the Schottky barrier height between Au and TiO2.•The hot electron ...injection efficiency from plasmonic Au to TiO2 is augumented.•Au/TiO2/rGO exhibits superior H2O oxidation performance compared with Au/TiO2.
Construction of plasmonic metal/semiconductor heterojunctions represents a promising approach to extending the light absorption range and simultaneously maintaining the high redox potentials of photogenerated carriers. However, unsuitable Schottky barrier height (ΦB) blocks the metal-to-semiconductor injection of hot electrons and increases the probability of their recombination with hot holes. Herein, a verstile protocol is demonstrated to address this issue based on the introduction of a reduced graphene oxide (rGO) substrate. As a proof-of-concept design, a Au/TiO2/rGO stacked photocatalyst is fabricated with TiO2 sandwiched between rGO and Au. In this smart design, rGO with work function smaller than that of Au upshifts the Fermi level of Au/TiO2 and reduces the ΦB between Au and TiO2. As a result, the hot electron injection efficiency from plasmonic Au to the conduction band of TiO2 is greatly augmented, increasing the number of separated hot holes participating in H2O oxidation. Profitting from the enhanced utilization of hot carriers, the Au/TiO2/rGO delivers markedly improved photocatalytic activity in O2 evolution as compared with Au/TiO2. This work provides us guidance to build high-efficient plasmonic photocatalysts for renewable fuel production and highlights the importance in reinforcing the separation and transfer of hot charges.
Product selectivity of alkyne hydroamination over catalytic Au2Co alloy nanoparticles (NPs) can be made switchable by a light‐on/light‐off process, yielding imine (cross‐coupling product of aniline ...and alkyne) under visible‐light irradiation, but 1,4‐diphenylbutadiyne in the dark. The low‐flux light irradiation concentrates aniline on the catalyst, accelerating the catalytic cross‐coupling by several orders of magnitude even at a very low overall aniline concentrations (1.0×10−3 mol L−1). A tentative mechanism is that Au2Co NPs absorb light, generating an intense fringing electromagnetic field and hot electrons. The sharp field‐gradient (plasmonic optical force) can selectively enhance adsorption of light‐polarizable aniline molecules on the catalyst. The light irradiation thereby alters the aniline/alkyne ratio at the NPs surface, switching product selectivity. This represents a new paradigm to modify a catalysis process by light.
Flicking the switch: The product selectivity of two competing reactions—alkyne hydroamination and alkyne–alkyne homo‐coupling—occuring on catalyst Au2Co alloy nanoparticles can be switched by visible‐light irradiation. Light irradiation concentrates aniline on the catalyst, accelerating the catalytic cross‐coupling by several orders of magnitude, while in the dark, homo‐coupling of two alkyne molecules is preferred.
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