Plasmonic Noble Metal Research Articles

Chiral Polar Bifunctional Polyimide Enantiomers for Asymmetric Photo- and Piezo-catalysis.

Chiral catalysts for asymmetric catalysis represent a crucial research focus in chemistry and materials science. However, a few cases about chiral-dependent photocatalysts primarily focus on plasmonic noble metals. Particularly, developing chiral nano-catalysts that can be driven by mechanical energy remains in the blank stage. Herein, organic polymer-based enantiomers, chiral polar polyimide (PI) microspheric nano-assembly are synthesized as novel bifunctional catalysts for asymmetric photocatalysis and piezocatalysis. The PI catalyst enantiomers present enantioselectivity towards left- and right-circularly polarized light, demonstrating chiral-dependent H2O2 photoproduction. Interestingly, enantioselectivity of the catalyst reverses under irradiation of different bands, presenting tunability in the interaction between chiral catalysts and circularly polarized light. For the first time, enantioselective piezocatalytic behavior is demonstrated by the chiral polar PI catalysts. They show remarkable chiral preference for asymmetric Diels-Alder reaction and enantioselective conversion of tyrosine substrates under ultrasonic vibration. The findings provide a new perspective into exploring metal-free chiral catalysts and their asymmetric catalysis applications across multiple energy forms.

Chiral Polar Bifunctional Polyimide Enantiomers for Asymmetric Photo‐ and Piezo‐catalysis

Chiral catalysts for asymmetric catalysis represent a crucial research focus in chemistry and materials science. However, a few cases about chiral‐dependent photocatalysts primarily focus on plasmonic noble metals. Particularly, developing chiral nano‐catalysts that can be driven by mechanical energy remains in the blank stage. Herein, organic polymer‐based enantiomers, chiral polar polyimide (PI) microspheric nano‐assembly are synthesized as novel bifunctional catalysts for asymmetric photocatalysis and piezocatalysis. The PI catalyst enantiomers present enantioselectivity towards left‐ and right‐circularly polarized light, demonstrating chiral‐dependent H2O2 photoproduction. Interestingly, enantioselectivity of the catalyst reverses under irradiation of different bands, presenting tunability in the interaction between chiral catalysts and circularly polarized light. For the first time, enantioselective piezocatalytic behavior is demonstrated by the chiral polar PI catalysts. They show remarkable chiral preference for asymmetric Diels‐Alder reaction and enantioselective conversion of tyrosine substrates under ultrasonic vibration. The findings provide a new perspective into exploring metal‐free chiral catalysts and their asymmetric catalysis applications across multiple energy forms.

Selective Photocatalytic CO2 Reduction Through Plasmonic Z‐Scheme Ag‐Bi2O3‐ZnO Heterostructures

AbstractCombination of plasmonic noble metal with semiconductors offers a promising and potential solar energy harvesting and conversion route. Herein, plasmonic Z‐scheme Ag‐Bi2O3‐ZnO (AgBZ) heterostructure is designed and synthesized via solution combustion and photo‐deposition method. Metallic Ag nanoparticles (NPs) were deposited over Bi2O3‐ZnO heterostructure; thus, they exhibit strong visible light absorption owing to surface plasmon resonance (SPR). The photocatalytic efficiency of the synthesized catalysts is investigated by the photocatalytic CO2 reduction to fuels under simulated solar light irradiation. The present system has shown an outstanding photocatalytic CO2 reduction and excellent selectivity of CO. The evolved rate of CO fuel, the amount of CO produced per unit time, over optimized Ag‐Bi2O3‐ZnO (3AgBZ) heterostructures was (96.74 μmol g−1/h) which was approximately 12 times larger than that of Bi2O3‐ZnO (0AgBZ) and 49‐fold than the quantity of evolved CO fuels over pure ZnO photocatalyst. The percentage of evolved CO to CH4 fuels over optimized Ag‐Bi2O3‐ZnO (3AgBZ) heterostructures was about 50 : 1compared to that of 2 : 3 over Bi2O3‐ZnO (0AgBZ). The great improvement and the high selectivity would be ascribed to the synergistic effect of metallic surface plasmon resonance and the Z‐scheme charges transfer system. This work would open a window to construct a single photocatalyst with different charge separation systems and excellent CO2 reduction selectivity. Finally, the mechanism for the enhanced photocatalytic performance by the synergistic effect was described and discussed.

Phase-Tunable Molybdenum Boride Ceramics as an Emerging Sensitive and Reliable SERS Platform in Harsh Environments.

Traditional surface-enhanced Raman scattering (SERS) sensors rely heavily on the use of plasmonic noble metals, which have limitations due to their high cost and lack of physical and chemical stability. Hence, it is imperative to explore new materials as SERS platforms that can withstand high temperatures and harsh conditions. In this study, the SERS effect of molybdenum boride ceramic powders is presented with an enhancement factor of 5 orders, which is comparable to conventional noble metal substrates. The molybdenum boride powders synthesized through liquid-phase precursor and carbothermal reduction have β-MoB, MoB2, and Mo2B5 phases. Among these phases, β-MoB demonstrates the most significant SERS activity, with a detection limit for rhodamine 6G (R6G) molecules of 10-9m. The impressive SERS enhancement can be attributed to strong molecule interactions and prominent charge interactions between R6G and the various phases of molybdenum boride, as supported by theoretical calculations. Additionally, Raman measurements show that the SERS activity remains intact after exposure to high temperature, strong acids, and alkalis. This research introduces a novel molybdenum boride all-ceramic SERS platform capable of functioning in harsh conditions, thereby showing the promising of boride ultrahigh-temperature ceramics for detection applications in extreme environments.

On the unique temperature-dependent interplay of a B-exciton and its trion in monolayer MoSe2.

Plasmonics in metal nanoparticles can enhance their near field optical interaction with matter, promoting emission into selected optical modes. Here, using Ga nanoparticles with carefully tuned plasmonic resonance in proximity to MoSe2 monolayers, we show selective photoluminescence enhancement from the B-exciton and its trion with no observable A-exciton emission. The nanoengineered substrate allows for the first direct experimental observation of the B-trion binding energy in semiconducting monolayers. Using temperature-dependent photoluminescence measurements, we show the following features of the MoSe2 B-exciton family: (i) the trion binding energy has an observable temperature dependence with a decreasing trend towards low temperatures and (ii) the exciton-trion emission ratio varies non-monotonically with temperature with a steep increase in the trion emission at lower temperatures. Using detailed models, we identify the particle size required for selective excitation and describe the underlying physical processes. This opens newer avenues for selectively promoting excitonic species and tuning the effective particle lifetimes in monolayer semiconductors. These results demonstrate the excellent plasmonic properties of Ga nanoparticles, which along with facile processing techniques makes it an attractive alternative to the prevalent noble metal plasmonics having applications in flexible/stretchable materials and textiles.

Bio‐Templated Silver Nanopatterns for Photothermal and Antifogging Coatings

AbstractTransparent photothermal coatings based on plasmonic noble metals often face a trade‐off between achieved temperatures and transmittances. This challenge arises from the fact that plasmonic nanoparticles (NPs), which rely on their size and structures, selectively absorb light of various wavelengths and convert it into heat. In the cases of randomly arranged plasmonic NPs, absorbances are predominantly in the visible range, leading to lowered transmittances. In this work, the self‐assembly behavior of a biotemplate containing flexible potato virus A (PVA) is used to produce network‐like surface patterns with controllable intermittent vacancies. These templates effectively anchor silver nanoparticles (AgNPs), forming dense arrays of plasmonic hotspots interspersed with vacant regions. With this approach, a temperature increase of 21 °C above ambient temperature under 1‐sun radiation is achieved while maintaining a visible light transmittance as high as 78% measured at 550 nm wavelength. The PVA biotemplated AgNPs show excellent potential as antifogging coating, exhibiting 2–3 times faster defogging rates compared to uncoated samples in both indoor and outdoor conditions. Overall, a platform is presented for biotemplating metal NPs, the development of long‐range surface patterns with controlled vacancies, and the demonstration of transparent photothermal activity with an antifogging application.

Colloidal Plasmonic TiN Nanoparticles for Efficient Solar Seawater Desalination.

Transferring traditional plasmonic noble metal nanomaterials from the laboratory to industrial production has remained challenging due to the high price of noble metals. The development of cost-effective non-noble-metal alternatives with outstanding plasmonic properties has therefore become essential. Herein, we report on the gram-scale production of differently shaped TiN nanoparticles with strong plasmon-enabled broadband light absorption, including differently sized TiN nanospheres, nanobipyramids, and nanorod arrays. The TiN nanospheres and nanobipyramids are further coembedded in highly porous poly(vinyl alcohol) films to function as a photothermal material for solar seawater desalination. A seawater evaporation rate of 3.8 kg m-2 h-1 is achieved, which marks the record performance among all plasmonic solar seawater desalination systems reported so far. The removal percentage of phenol reaches 98.3%, which is attributed to the joint action of the excellent photocatalytic ability and the superhydrophilicity of the porous TiN-based composite film.

THz time-domain spectroscopy modulated with semiconductor plasmonic perfect absorbers.

Terahertz time-domain spectroscopy (THz-TDS) at room temperature and standard atmosphere pressure remains so far the backbone of THz photonics in numerous applications for civil and defense levels. Plasmonic microstructures and metasurfaces are particularly promising for improving THz spectroscopy techniques and developing biomedical and environmental sensors. Highly doped semiconductors are suitable for replacing the traditional plasmonic noble metals in the THz range. We present a perfect absorber structure based on semiconductor III-Sb epitaxial layers. The insulator layer is GaSb while the metal-like layers are Si doped InAsSb (∼5·1019 cm-3). The doping is optically measured in the IR with polaritonic effects at the Brewster angle mode. Theoretically, the surface can be engineered in frequency selective absorption array areas of an extensive THz region from 1.0 to 6.0 THz. The technological process is based on a single resist layer used as hard mask in dry etching defined by electron beam lithography. A wide 1350 GHz cumulative bandwidth experimental absorption is measured in THz-TDS between 1.0 and 2.5 THz, only limited by the air-exposed reflectance configuration. These results pave the way to implement finely tuned selective surfaces based on semiconductors to enhance light-matter interaction in the THz region.

Plasmonic Nanomaterials for Micro- and Nanoplastics Detection

Detecting and quantifying micro- and nanoplastics (MNPs) in the environment is a crucial task that needs to be addressed as soon as possible by the scientific community. Many analytical techniques have been proposed, but a common agreement on analytical protocols and regulations still has to be reached. Nanomaterial-based techniques have shown promising results in this field. In this review, we focus on the recent results published on the use of plasmonic noble metal materials for the detection of MNPs. Plasmonic materials can be exploited in different ways due to their peculiar optical end electronic properties. Surface plasmon resonance, plasmon enhanced fluorescence, UV–Vis spectroscopy, and surface enhanced Raman scattering (SERS) will be considered in this review, examining the advantages and drawbacks of each approach.

Bi-MOF-derived plasmonic Bi-C on carbon felt for efficient solar evaporation, water purification and salt-resistant desalination

Plasmonic nanostructures have been demonstrated to be an important class of photothermal absorbers, facilitating solar vapor generation by plasmonic heating. However, the high cost and sophisticated preparation of commonly used plasmonic noble metals pose significant obstacles to practical applications. Here, we report for the first time an affordable plasmonic evaporation system that combines the porous carbon frameworks encapsulated semimetal Bi nanoparticles (Bi-C) and carbon felt (CF). The hydrophilic Bi-C and porous network structure of CF favor effective light harvesting and fast water transmission, promoting photothermal conversion and mass transfer during solar evaporation. Under one sun irradiation, the designed Bi-C/CF exhibits the robust behavior for solar steam generation, achieving an expected high evaporation rate of 1.50 kg·m−2·h−1 and a comparable evaporation efficiency of 91.9 %. As a result, the excellent performance of Bi-C/CF not only benefits the sustainable freshwater production from saline water and seawater, but also enables efficient wastewater purification for energy-saving water source remediation.

Smart Design of Noble Metal–Copper Chalcogenide Dual Plasmonic Heteronanoarchitectures for Emerging Applications: Progress and Prospects

Dual plasmonic metal–semiconductor heteronanostructures have been actively investigated due to their outstanding functional characteristics arising from the merging of two materials. In this review, the synthetic approaches, various designs, enhanced properties, and prospective applications of noble metal–nonstoichiometric copper chalcogenide nanosystems are summarized. The tunable size, shape, structure type (solid or hollow), composition, and doping level of the constituents produce several configurations of heteronanocomposites reported here. The colloidal synthetic approaches for the fabrication of dual plasmonic nanomaterials with controllable plasmonic properties are presented as well. The unique features of dual plasmonic nanostructures show synergistic and plasmon resonance coupling effects and enhanced light–matter interactions, which cannot be simply assigned to the mixture of pristine materials. Dual plasmonic hybrid nanosystems are promising candidates for enhanced photocatalysis, photothermal cancer therapy, improved sensing, photovoltaic devices, and upconversion luminescence. In conclusion, a brief outlook of the identified challenges in the area of dual plasmonic noble metal–vacancy-doped copper chalcogenide nanomaterials to be addressed in the nearest future is provided.

Flexible SERS strip based on HKUST-1(cu)/biomimetic antibodies composite multilayer for trace determination of ethephon

A surface-enhanced Raman scattering (SERS) sensor based on the folding and assembly characteristics of the three-dimensional structure of paper fibers, the skeleton controllability of metal-organic framework materials (MOFs), and the morphology designability of plasmonic noble metal materials has been established for rapid on-site determination of ethephon in food. HKUST-1(Cu) was assembled onto a carbon-treated chromatographic paper matrix by electrodeposition, and its skeleton respiration and sponge effect were used to overcome the bottleneck problem of poor affinity of SERS substrate for target molecules. Further coupled with the targeted recognition specificity of biomimetic antibodies, a paper-based interface with high specificity of molecular sensitivity was constructed. A sandwich multi-stage progressive enhancement structure was designed to couple plasma pine branch-shaped silver material in situ at the interface to realize superposition and collaborative amplification of SERS signals. When the paper-based strip sensor was used to monitor ethephon, it demonstrated a linear range of 10−3 to 10 mg kg−1 and a detection limit of around 1.39 × 10−4 mg kg−1. The construction and application of the paper-based HKUST-1(Cu)/biomimetic antibodies/pine branch-shaped silver material sensor will provide technical means and theoretical support for the rapid and efficient identification of biological ripening agent residues in food with multi-level signal enhancement.

Insights into the Machine Learning Predictions of the Optical Response of Plasmon@Semiconductor Core-Shell Nanocylinders

The application domain of deep learning (DL) has been extended into the realm of nanomaterials, photochemistry, and optoelectronics research. Here, we used the combination of a computer vision technique, namely convolutional neural network (CNN), with multilayer perceptron (MLP) to obtain the far-field optical response at normal incidence (along cylinder axis) of concentric cylindrical plasmonic metastructures such as nanorods and nanotubes. Nanotubes of Si, Ge, and TiO2 coated on either their inner wall or both their inner and outer walls with a plasmonic noble metal (Au or Ag) were thus modeled. A combination of a CNN and MLP was designed to accept the cross-sectional images of cylindrical plasmonic core-shell nanomaterials as input and rapidly generate their optical response. In addition, we addressed an issue related to DL methods, namely explainability. We probed deeper into these networks’ architecture to explain how the optimized network could predict the final results. Our results suggest that the DL network learns the underlying physics governing the optical response of plasmonic core-shell nanocylinders, which in turn builds trust in the use of DL methods in materials science and optoelectronics.

Flexible optical limiters based on Cu3VSe4 nanocrystals.

Optical limiters are greatly needed to protect eyes and sensitive optoelectronic devices such as photodetectors and sensors from laser damage, but they are currently plagued by low efficiency. In this work, we utilized Cu3VSe4 nanocrystals (NCs) to enhance laser protection performance, and they exhibit higher saturation intensity and broader nonlinear spectral response extending into the near IR region than the C60 benchmark. A flexible optical limiter goggle prototype based on the NCs significantly attenuated the incident laser beam, with Z scan and I scan measurements demonstrating a giant nonlinear absorption coefficient β value of 1.0 × 10-7 m W-1, a large optical damage threshold of 3.5 J cm-2, and a small starting threshold of 0.22 J cm-2. Transient absorption spectroscopy disclosed that the origin of the excellent nonlinearity was associated with quasi-static dielectric resonance behavior and a large TPA cross-section of 3.3 × 106 GM was measured for Cu3VSe4 NCs, suggesting the potential of intermediate bandgap (IB) semiconductors as alternatives to plasmonic noble metals for ultrafast photonics. Hence, optical limiters based on such semiconductors offer new avenues for laser protection in optoelectronic and defense fields.

Photo-activation of Ag chemicals for enhanced Nb2O5 optoelectronic device employing plasmonic effects

This new work contributes to enhance the pulsed laser fabricated Nb2O5 nanostructures via silver (Ag) NPs plasmonic noble metal for the first time, for the best of our knowledge. Silver (Ag) NPs were incorporated into Nb2O5 nanomatrix structure by UV photo-activation mechanism of Nb2O5 immersed in AgNO3 for 5, 15, 25, 35, and 45 s, respectively. The results revealed that the optical band gap of Nb2O5 was reduced from 3.37 to 3.28 eV when silver (Ag) NPs were incorporated. Photoluminescence (PL) analyzes showed an enhanced Nb2O5 quality by showing defects reduction within the UV region (<375 nm) of the emission wavelengths. XRD analyzes revealed the successful decoration of silver (Ag)NPs into Nb2O5 nanostructure by showing silver diffraction planes at (200) and (111) among Nb2O5 diffraction planes. Surface-enhanced Raman spectroscopic (SERS) analyzes revealed an enhancement in the monoclinic (HNb2O5) at 1156.2 cm−1 demonstrating a successful hot electrons transfer.

A novel Ag/g-C3N4/ZnO/Fe3O4 nanohybrid superparamagnetic photocatalyst for efficient degradation of emerging pharmaceutical contaminant (Pantoprazole) from aqueous sources

Owing to their remarkable properties, such as concentration of energetic photons, scattering of photons and demonstration of surface plasmon resonance (SPR), the use of plasmonic noble metals in the construction of a nanohybrid photocatalyst holds great promise of enhancing photodegradation rates. The current work puts forth a facile route of fabrication of a robust Ag/g-C3N4/ZnO/Fe3O4 hybrid, superparamagnetic nano-photocatalyst for express photodegradation of pantoprazole, a prototype of a pharmaceutical. The absorption edge of the nano-scaled hybrid photocatalyst was found to be ~ 2.25 eV suggesting fine-tuning of band edges of its moieties. Photoluminescence studies and photoelectrochemical investigations of the hybrid photocatalyst revealed a diminished rate of electron-hole recombination that further suggested enhanced separation of charge carriers attained through synergistic effects of individual moieties. g-C3N4 and Fe3O4 proved to be of immense consequence vis-à-vis separation of photoinduced charge carriers. Alone the photocatalyst achieved 98.24% disintegration of pantoprazole within 40 min with a stupendous pseudo-first order velocity constant of 0.10231 min−1. The performance of the quaternary photocatalyst was also evaluated in presence of various co-existing substances as well as in environmental water samples.

Ultrathin Film Amorphous Silicon Solar Cell Performance using Rigorous Coupled Wave Analysis Method

The issues related to global energy needs and environmental safeties as well as health crisis are some of the major challenges faced by the human, which make us to generate new pollution-free and sustainable energy sources. For that the optical functional nanostructures can be manipulated the confined light at the nanoscale level. These characteristics are emerging and leading candidate for the solar energy conversion. The combination of photonic (dielectric) and plasmonic (metallic) nanostructures are responsible for the development of better optical performance in solar cells. Here, the enhancement of light trapping within the thin active region is the primary goal. In this work, we have studied the influence of front-ITO (rectangular) and back-Ag (triangular) nanogratings were incorporated with ultrathin film amorphous silicon (a-Si) solar cell by using rigorous coupled wave analysis (RCWA) method. The improvement of light absorption, scattering (large angle), diffraction and field distributions (TE/TM) were demonstrated by the addition of single and dual nanogratings structures. Significantly, the plasmonic (noble metal) nanogratings are located at the bottom of the cell structure as a backside reflector which is helpful for the omni-directional reflection and increased the path length (life time) of the photons due to that the collection of the charge carriers were enhanced. Further, the proposed solar cell structure has optimized and compared to a back-Ag, front-ITO and dual nanogratings based ultrathin film amorphous silicon solar cell. Finally, the obtained results were evidenced for the assistance of photonic and plasmonic modes and achieved the highest current density (Jsc) of 23.82 mA/cm2(TE) and 22.75 mA/cm2 (TM) with in 50 nm thin active layers by integration of (dual) cell structures.

Plasmonic photoelectrochemical reactions on noble metal electrodes of nanostructures

Plasmonic noble metal nanostructures have been targeted due to their strong surface plasmon resonance at photoelectrochemical interfaces. Recently, it has been concluded that, the plasmonic noble metal nanostructures on photoexcitation permit the transfer of effective hot carriers (hot electron/hole pair) to nearby adsorbed molecules where, the transformed hot carriers can efficiently decrease the activation barrier of a reaction. In this review, our recent achievements in the plasmon-mediated chemical reactions of organic molecules such as para -aminothiophenol, substituted para -aminothiophenol and para -nitrothiophenol at nanostructures modified noble metal electrodes using surface enhanced Raman spectroscopy, electrochemical methods, and theoretical calculations will be discussed.

Nanomaterial-based single-molecule optical immunosensors for supersensitive detection

Unlike bulk materials, nanomaterials have unique properties that make them suitable for biosensor applications. Nanomaterial-based biosensors have a series of advantages that can help realize high throughput and ultrasensitive detection. In recent years, considerable research has been performed on integrating nanomaterials and single-molecule immunosensors. This review provides an overview on the various types of nanomaterials used for signal amplification in single-molecule immunosensors, with a focus on the development of optics-based immunosensors using precious plasmonic noble metals (e.g., gold, silver), magnetic beads, quantum dots, upconversion nanoparticles, and nanocomposites. In particular, an approach is presented of using single-molecule immunosensors to detect and quantify biomolecular interactions (e.g., antibody–antigen). Integrating supersensitive bio-devices and nanomaterials is expected to offer significant advantages for trace element diagnosis and early diagnosis.

(Digital Presentation) The Photoresponse Enhancement of Graphene Photodetector By Metasurface Under Mid-Infrared Region

As a zero bandgap material, graphene has excellent optical properties and electrical doping characteristics. Graphene plasmons exhibit much larger confinement and longer propagation distances than noble-metal plasmons. The surface plasmons technique has been widely used in photodetectors because it can couple light to the devices for signal detection. In this paper, we combine graphene with existing surface-plasmon-based devices and show that the photocurrent is twice as intrinsic graphene devices under the same infrared light source. Metasurface on graphene/SiO2 under infrared light will induce plasmon–phonon quasi-particle, which will decay into electron-hole pairs and phonons. The former increases the total transport current and dominates in the graphene lightly doping condition. The latter decreases the total transport current and dominates in the graphene highly doping condition. As a result, the responsivity can be tailored by Fermi-level tuning. We demonstrate that the responsivity of the metasurface graphene photodetector can reach the ~5e-4 A/W in the mid-infrared region. It's believed that the high responsivity and photoresponse modulation has promising and flexible application scenarios in photodetectors.