Plasmonic Absorption Properties Research Articles

Hybrid nanoarchitectonics of carbon/titanium carbide integrated hydrogel/melamine foam for highly efficient solar steam and thermoelectric power generation

Solar driven interface water evaporation, a feasible approach to solve the global water crisis, requires a rational combination of high efficiency photothermal material and evaporation structure. In this paper, carbon/titanium carbide (C/TiC) nanohybrids from Ti-based metal-organic framework (Ti-MOF) were controllable synthesized and applied for highly efficient solar steam and thermoelectric power generation. Considering inherent defects of single-component materials, the synthesized unique porous C/TiC nanohybrids exhibit both lattice resonance and plasmonic absorption properties, achieving a high solar-steam conversion efficiency of 90 %. Further, a multi-structured hydrogel (TMH) was prepared by dipping porous melamine foam in gel containing porous C/TiC nanohybrids, and a high evaporation rate of 1.93 kg m−2 h−1 under one sun irradiation has been achieved for its excellent light absorption performance and thermal management ability. Long-term desalting experiments exhibit TMH presents desirable self-cleaning characteristic and can meet its performance requirements in 3.5–20 wt% brine. More importantly, as a proof-of-concept demonstration of synergistic solar steam and thermoelectric power generation, the synergistic system simultaneously realized a high evaporation rate of 0.93 kg m−2 h−1 and produced a stable voltage up to 150 mV under one sun irradiation. This solar-thermal evaporation and thermoelectric generation technology provides a promising avenue for practical desalination and thermoelectric power generation.

Nanosecond Laser–Assisted Tuning of the Plasmon Band of Triangular-Shaped Ag Nanostructures and Development of a Broadband Visible-Near Infrared Light Absorber

Most of the outstanding applications of silver nanoparticles (Ag NPs) have arisen from their tunable localized surface plasmon resonance (LSPR). In this report, we have systematically studied the photothermal transformation of morphology of triangular-shaped Ag NPs (TSNP) under irradiation of a nanosecond (ns)-pulsed laser of 1064-nm wavelength with the pulse duration of 10 ns at different laser fluence and irradiation time. Interestingly, at a typical value of fluence of 104–174 J/cm2 both the triangular and plate-like Ag NPs are transformed into spherical Ag NPs of size ~ 5 nm in just 20–40 min of irradiation that is found to be very much faster when it is compared with the results of well-known chemically etching–based reshaping process in the presence of KBr. We have also demonstrated the possible use of the plasmonic absorption properties of the triangular, plate-like and transformed spherical Ag NPs for the development of a broad-band visible-NIR light absorber by just mixing these Ag NPs of three different morphologies. We have got almost 20% average (overall below 35%) transmission in the wavelength range from 400 to 800 nm in the liquid phase and 57% (overall below 65%) when NPs are put into PVA matrix in 16 vol%. The applicability of the prepared broadband absorber is being verified by monitoring the current response of a light-dependent resistor and degradation process of rhodamine 6G dye in sunlight.

Monolayer and thin h–BN as substrates for electron spectro-microscopy analysis of plasmonic nanoparticles

The influence of four substrates [thin Si3N4, few-layer graphene (FLG), thin h–BN, and monolayer h–BN] on plasmon resonances of metallic nanoparticles was studied using electron energy loss spectroscopy. The h–BN monolayer is an excellent substrate for the study of plasmonic particles due to its large bandgap, negligible charging under electron irradiation, and negligible influence on the plasmon resonance full width at half maximum and peak positions. These effects were evidenced in experiments with gold nanotriangles focusing on dipolar modes. Nanotriangles on h–BN exhibit the lowest influence from the substrate compared to Si3N4 and FLG. In a dataset containing 23 triangles of similar sizes, the dipolar mode was found to have smaller redshifts, sharper peak widths, and higher resonance quality factors on h–BN, showing that it has nearly no effect on the plasmon absorption properties, provided that it is free from carbon contamination. However, light emission (cathodoluminescence) decreases as a function of electron irradiation for triangles on h–BN, even though the electron energy loss signal stays unchanged. This indicates the creation of non-radiative decay channels.

Plasmonic enhancement for high efficient and stable perovskite solar cells by employing "hot spots" Au nanobipyramids

Metal plasmonic effect is one promising way for improving the performance and stability of the perovskite solar cells via optical-electrical behalves, and the ability is in proportion to the enhanced local electromagnetic fields induced by metal nanostructures. In our work, unique gold nanobipyramids (Au NBs) structures were explored and incorporated in the hole transport layer of planar heterojunction PSCs. This typical "bipyramid-like" metal nanostructure with sharp tips has the multiple and strong plasmonic absorption properties from visible to the NIR, exhibiting high plasmonic-induced probability. In addition, generated "hot spots" around Au NBs provided much stronger EM fields enhancements than conventional Au nanoparticles, hence enhanced light harvesting and improved interfacial charge dynamic process can be achieved simultaneously. As for the further investigation of the electrical property, hot holes injection induced by Au NBs effectively filled in the interfacial traps under operation condition, contributing to the improvement of the open circuit voltage, the elimination of the hysteresis effect and the long-term stability. Accordingly, the best PSC incorporated with Au NBs showed the PCE of 18.84% whereas the reference device just showed the PCE of 16.02%. Our work demonstrated that plasmonic metal nanostructures possessing the feature of "hot spots" offered a great potential to further expand the performance limitation and operation tolerance of the PSCs.

Defects-assisted solar absorption of plasmonic nanoshell-based nanofluids

Plasmonic nanoshell-based nanofluids have recently been demonstrated to be promising candidates for efficient solar thermal conversion. During the nanoshells’ fabrication processes, more often than not, only part of the dielectric core is covered by metals. However, there are few reports on how these particle defects affect the solar thermal conversion. In this paper, we find that the coverage defects of TiO2/Ag nanoshells, instead of deteriorating, may enhance the solar absorption of nanofluids. The underlying mechanism mainly lies in the redshift of the symmetric localized surface plasmon resonance from the visible region for perfect nanoshells to the near-infrared in the presence of particle defects. The poor absorption of perfect nanoshells based nanofluids in the near-infrared is thus improved. The redshift can be quantitatively predicted and understood by an effective medium approach. This work opens a new route to enhance the solar thermal conversion of nanofluids by mediating the resonance absorption of composite nanoparticles via defects, and helps to deepen the understanding of plasmonic absorption properties of non-perfect nanoshells.

Fabrication and optical property of metal nanowire arrays embedded in anodic porous alumina membrane

Nanowires embedded in nanopores are potentially tough against surface scraping and agglomeration. In this study, we have fabricated Au and Ni nanowires embedded into anodic porous alumina (APA) and investigated their reflectance to study the effects of surface plasmon absorption properties and conversion from solar energy to thermal energy. Au nanowires embedded into APA show typical gold surface plasmon absorption at approximately 530 nm. On the other hand, Ni nanowires show quite a low reflectance under 600 nm. In the temperature elevation test, both Au and Ni nanowire samples present the same capability to warm up water. It means that Ni nanowires embedded into APA have almost the same photothermal activity as Au nanowires.

Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite

Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors (band-pass filters with high reflectivity) represent good candidates. However, their optical characteristics are determined during the fabrication stage. Heavily doped semiconductor nanocrystals (NCs), on the other hand, deliver a high degree of optical tunability through the active modulation of their carrier density, ultimately influencing their plasmonic absorption properties. Here, we propose the design of an actively tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis–NIR) spectral region when employing varying carrier densities. As the tunable component, we implemented a dispersion of copper selenide (Cu2−xSe) NCs and a film of indium tin oxide (ITO) NCs, which are known to show optical tunablility with chemical or electrochemical treatments. We utilized the Mie theory to describe the carrier-dependent plasmonic properties of the Cu2−x Se NC dispersion and the effective medium theory to describe the optical characteristics of the ITO film. The transmission properties of the Bragg mirror have been modelled with the transfer matrix method. We foresee ease of experimental realization of the coupled device, where filtering modulation is achieved upon chemical and electrochemical post-fabrication treatment of the heavily doped semiconductor NC component, eventually resulting in tunable transmission properties of the coupled device.

The Effect of Metal Type on the Separate Dielectric Layer-Dependent Plasmon Coupling in Al–Au Bimetallic Metal-Dielectric-Metal Nanoshells

Metal type-dependent plasmonic absorption properties of Al–Au bimetallic metal-dielectric-metal nanoshells have been investigated theoretically by using the quasi-static theory of classical electrodynamics. It has been found that the three-layered nanoshells present different surface plasmon resonance (SPR) properties when the metal type of the inner core and outer shell is exchanged. For Al-dielectric-Au nanoshell, the |ω−−〉 band takes the major role of the absorption spectrum. Whereas for Au-dielectric-Al nanoshell, the |ω−+〉 mode has the highest intensity. The corresponding physical origin has been attributed to the different optical parameters of Au and Al, which results in different local field enhancement and plasmon energy at each plasmon hybridization mode. The plasmonic absorption properties also depend on the thickness of the separate layer and are further affected by the metal type of the inner core and outer shell. For Al-dielectric-Au nanoshell, the increasing separate layer thickness results in distinct red shift of |ω−+〉 peak but slight blue shift of the |ω+−〉 peak. For Au-dielectric-Al nanoshell, the |ω+−〉 and |ω−+〉 modes fade down and blue shifts, whereas the major peak corresponding to the |ω−−〉 mode blue shifts and gets intense firstly and then red shifts and decreases as the thickness is increased. These results indicate that different plasmon hybridization modes of the multilayered nanoshell could be enhanced selectively by choosing different type of metal as the outer shell.

Light‐Induced Plasmon‐Assisted Phase Transformation of Carbon on Metal Nanoparticles

AbstractHighly localized light‐induced phase transformation of electron beam induced deposited carbon nanostructures (dots and squares) on noble metal surfaces is reported. The phase transformation from the amorphous phase to the disordered graphitic phase is analyzed using the characteristic Raman signatures for amorphous and graphitized carbon and conductive force microscopy. The extent of the transformation is found to be largely dependent on the plasmon absorption properties of the underlying metal film. It is observed that the amorphous carbon deposits on the silver films consisting of 12 nm particles with the plasmon absorption near the laser excitation wavelength (514 nm), undergo fast graphitization to a nanocrystalline or a disordered graphitic phase. This transformation results in the formation of a highly conductive carbon/metal interface with at least seven orders of magnitude lower electrical resistivity than the initial insulating interface. It is suggested that the fast graphitization of nanoscale carbon deposits might serve as an efficient path for the formation of complex patterned nanoscale metal‐carbon interconnects with high electrical conductivity.

Tunable infrared plasmonic absorption by metallic nanoparticles

We exploit unique infrared plasmonic absorption properties of gold (Au) nanoparticles in the range of 2.5 to 20 μm. Fabrication of Au nanoplasmon particles with variable nanometer (nm) scale size and thickness gave us full control of tuning the absorption wavelength in the above infrared (IR) spectral regions. We did not observe polarization dependence for square size plasmon particles. However, by using plateau crescent (metal crescent structure with flat instead of rounded side on the top) metal particles we observed significant polarization effects in IR absorption spectra. We observed that the position of the absorption peak has linear dependence on the size of nanoparticles, and the absorption quantity depends on the density of the nanoparticles per unit area. The proposed nanoplasmon structure can be used to improve the performance of detector and light emitting diode (LED) devices operating in the IR region.

Optically Addressable Nanostructured Capsules

The preparation of near-infrared (NIR) responsive capsules based on gold nanoparticle incorporated within a layer-by-layer assembled polyelectrolyte multilayer shell was analyzed. These core-shell structures had tunable plasmon absorption properties in the NIR. It was observed that such optically addressable capsules could release encapsulated biomaterials on demand upon irradiation with short-pulsed laser light. It was also observed that the capsules could be coated with lipid bilayers, which was then functionalized with antibodies in order to impart biorecognition capabilities.