R-3 Repository :: Browsing by Author "Alabastri, Alessandro"

Browsing by Author "Alabastri, Alessandro"

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A biophysically constrained brain connectivity model based on stimulation-evoked potentials.
(Elsevier, 2024) Schmid, William; Danstrom, Isabel A.; Crespo Echevarria, Maria; Adkinson, Joshua; Mattar, Layth; Banks, Garrett P.; Sheth, Sameer A.; Watrous, Andrew J.; Heilbronner, Sarah R.; Bijanki, Kelly R.; Alabastri, Alessandro; Bartoli, Eleonora
Background Single-pulse electrical stimulation (SPES) is an established technique used to map functional effective connectivity networks in treatment-refractory epilepsy patients undergoing intracranial-electroencephalography monitoring. While the connectivity path between stimulation and recording sites has been explored through the integration of structural connectivity, there are substantial gaps, such that new modeling approaches may advance our understanding of connectivity derived from SPES studies. New method Using intracranial electrophysiology data recorded from a single patient undergoing stereo-electroencephalography (sEEG) evaluation, we employ an automated detection method to identify early response components, C1, from pulse-evoked potentials (PEPs) induced by SPES. C1 components were utilized for a novel topology optimization method, modeling 3D electrical conductivity to infer neural pathways from stimulation sites. Additionally, PEP features were compared with tractography metrics, and model results were analyzed with respect to anatomical features. Results The proposed optimization model resolved conductivity paths with low error. Specific electrode contacts displaying high error correlated with anatomical complexities. The C1 component strongly correlated with additional PEP features and displayed stable, weak correlations with tractography measures. Comparison with existing method Existing methods for estimating neural signal pathways are imaging-based and thus rely on anatomical inferences. Conclusions These results demonstrate that informing topology optimization methods with human intracranial SPES data is a feasible method for generating 3D conductivity maps linking electrical pathways with functional neural ensembles. PEP-estimated effective connectivity is correlated with but distinguished from structural connectivity. Modeled conductivity resolves connectivity pathways in the absence of anatomical priors.
All-Optical Reconfiguration of Ultrafast Dichroism in Gold Metasurfaces
(Wiley, 2022) Schirato, Andrea; Toma, Andrea; Proietti Zaccaria, Remo; Alabastri, Alessandro; Cerullo, Giulio; Della Valle, Giuseppe; Maiuri, Margherita
Optical metasurfaces have come into the spotlight as a promising platform for light manipulation at the nanoscale, including ultrafast all-optical control via excitation with femtosecond laser pulses. Recently, dichroic metasurfaces have been exploited to modulate the polarization state of light with unprecedented speed. This work theoretically predicts and experimentally demonstrates by pump–probe spectroscopy the capability to reconfigure the ultrafast dichroic signal of a gold metasurface by simply acting on the polarization of the pump pulse, which is shown to reshape the spatio-temporal distribution of the optical perturbation. The photoinduced anisotropic response, driven by out-of-equilibrium carriers and extinguished in a sub-picosecond temporal window, is readily controlled in intensity by tuning the polarization direction of the excitation up to a full sign reversal. Hence, nonlinear metasurfaces are here demonstrated to offer the flexibility to tailor their ultrafast optical response in a fully all-optically reconfigurable platform.
All-Optically Reconfigurable Plasmonic Metagrating for Ultrafast Diffraction Management
(American Chemical Society, 2021) Schirato, Andrea; Mazzanti, Andrea; Proietti Zaccaria, Remo; Nordlander, Peter; Alabastri, Alessandro; Della Valle, Giuseppe; Laboratory for Nanophotonics
Hot-electron dynamics taking place in nanostructured materials upon irradiation with fs-laser pulses has been the subject of intensive research, leading to the emerging field of ultrafast nanophotonics. However, the most common description of nonlinear interaction with ultrashort laser pulses assumes a homogeneous spatial distribution for the photogenerated carriers. Here we theoretically show that the inhomogeneous evolution of the hot carriers at the nanoscale can disclose unprecedented opportunities for ultrafast diffraction management. In particular, we design a highly symmetric plasmonic metagrating capable of a transient symmetry breaking driven by hot electrons. The subsequent power imbalance between symmetrical diffraction orders is calculated to exceed 20% under moderate (∼2 mJ/cm2) laser fluence. Our theoretical investigation also indicates that the recovery time of the symmetric configuration can be controlled by tuning the geometry of the metaatom, and can be as fast as 2 ps for electrically connected configurations.
Chiral Plasmonic Pinwheels Exhibit Orientation-Independent Linear Differential Scattering under Asymmetric Illumination
(American Chemical Society, 2023) McCarthy, Lauren A.; Verma, Ojasvi; Naidu, Gopal Narmada; Bursi, Luca; Alabastri, Alessandro; Nordlander, Peter; Link, Stephan
Plasmonic nanoantennas have considerably stronger polarization-dependent optical properties than their molecular counterparts, inspiring photonic platforms for enhancing molecular dichroism and providing fundamental insight into light-matter interactions. One such insight is that even achiral nanoparticles can yield strong optical activity when they are asymmetrically illuminated from a single oblique angle instead of evenly illuminated. This effect, called extrinsic chirality, results from the overall chirality of the experimental geometry and strongly depends on the orientation of the incident light. Although extrinsic chirality has been well-characterized, an analogous effect involving linear polarization sensitivity has not yet been discussed. In this study, we investigate the differential scattering of rotationally symmetric chiral plasmonic pinwheels when asymmetrically irradiated with linearly polarized light. Despite their high rotational symmetry, we observe substantial linear differential scattering that is maintained over all pinwheel orientations. We demonstrate that this orientation-independent linear differential scattering arises from the broken mirror and rotational symmetries of our overall experimental geometry. Our results underscore the necessity of considering both the rotational symmetry of the nanoantenna and the experimental setup, including illumination direction and angle, when performing plasmon-enhanced chiroptical characterizations. Our results demonstrate spectroscopic signatures of an effect analogous to extrinsic chirality for linear polarizations.
Controlling Light, Heat, and Vibrations in Plasmonics and Phononics
(Wiley, 2020) Cunha, Joao; Guo, Tian-Long; Valle, Giuseppe Della; Koya, Alemayehu Nana; Zaccaria, Remo Proietti; Alabastri, Alessandro
Plasmonic nanostructures have attracted considerable attention for their ability to couple with light and provide strong electromagnetic energy confinement at subwavelength dimensions. The absorbed portion of the captured electromagnetic energy can lead to significant heating of both the nanostructure and its surroundings, resulting in a rich set of nanoscale thermal processes that defines the subfield of thermoplasmonics with applications ranging from nanochemistry and nanobiology to optoelectronics. Recently, phononic nanostructures have started to attract attention as a platform for manipulation of phonons, enabling control over heat propagation and/or mechanical vibrations. The complex interaction phenomena between photons, electrons, and phonons require appropriate modelling strategies to design nanodevices that simultaneously explore and exploit the optical, thermal, and mechanical degrees of freedom. Examples of such devices are micro- and nanoscale opto-thermo-mechanical systems for sensing, imaging, energy conversion, and harvesting applications. Here, an overview of the fundamental theory and concepts crucial to the modelling of plasmo-phonon devices is provided. Particular attention is given to micro- and nanoscale modelling frameworks, highlighting their validity ranges and the experimental works that contributed to their validation and led to compelling applications. Finally, an open-ended outlook focused on emerging applications at the intersection between plasmonics and phononics is presented.
Dry synthesis of bi-layer nanoporous metal films as plasmonic metamaterial
(De Gruyter, 2024) Caligiuri, Vincenzo; Kwon, Hyunah; Griesi, Andrea; Ivanov, Yurii P.; Schirato, Andrea; Alabastri, Alessandro; Cuscunà, Massimo; Balestra, Gianluca; Luca, Antonio De; Tapani, Tlek; Lin, Haifeng; Maccaferri, Nicolò; Krahne, Roman; Divitini, Giorgio; Fischer, Peer; Garoli, Denis
Nanoporous metals are a class of nanostructured materials finding extensive applications in multiple fields thanks to their unique properties attributed to their high surface area and interconnected nanoscale ligaments. They can be prepared following different strategies, but the deposition of an arbitrary pure porous metal is still challenging. Recently, a dry synthesis of nanoporous films based on the plasma treatment of metal thin layers deposited by physical vapour deposition has been demonstrated, as a general route to form pure nanoporous films from a large set of metals. An interesting aspect related to this approach is the possibility to apply the same methodology to deposit the porous films as a multilayer. In this way, it is possible to explore the properties of different porous metals in close contact. As demonstrated in this paper, interesting plasmonic properties emerge in a nanoporous Au–Ag bi-layer. The versatility of the method coupled with the possibility to include many different metals, provides an opportunity to tailor their optical resonances and to exploit the chemical and mechanical properties of components, which is of great interest to applications ranging from sensing, to photochemistry and photocatalysis.
Electrostatic polarization fields trigger glioblastoma stem cell differentiation
(Royal Society of Chemistry, 2022) Cabada, Tamara Fernandez; Ruben, Massimo; Merhie, Amira El; Zaccaria, Remo Proietti; Alabastri, Alessandro; Petrini, Enrica Maria; Barberis, Andrea; Salerno, Marco; Crepaldi, Marco; Davis, Alexander; Ceseracciu, Luca; Catelani, Tiziano; Athanassiou, Athanassia; Pellegrino, Teresa; Cingolani, Roberto; Papadopoulou, Evie L.
Over the last few years it has been understood that the interface between living cells and the underlying materials can be a powerful tool to manipulate cell functions. In this study, we explore the hypothesis that the electrical cell/material interface can regulate the differentiation of cancer stem-like cells (CSCs). Electrospun polymer fibres, either polyamide 66 or poly(lactic acid), with embedded graphene nanoplatelets (GnPs), have been fabricated as CSC scaffolds, providing both the 3D microenvironment and a suitable electrical environment favorable for CSCs adhesion, growth and differentiation. We have investigated the impact of these scaffolds on the morphological, immunostaining and electrophysiological properties of CSCs extracted from human glioblastoma multiform (GBM) tumor cell line. Our data provide evidence in favor of the ability of GnP-incorporating scaffolds to promote CSC differentiation to the glial phenotype. Numerical simulations support the hypothesis that the electrical interface promotes the hyperpolarization of the cell membrane potential, thus triggering the CSC differentiation. We propose that the electrical cell/material interface can regulate endogenous bioelectrical cues, through the membrane potential manipulation, resulting in the differentiation of CSCs. Material-induced differentiation of stem cells and particularly of CSCs, can open new horizons in tissue engineering and new approaches to cancer treatment, especially GBM.
Flow-Driven Resonant Energy Systems
(American Physical Society, 2020) Alabastri, Alessandro
Here we provide a physical and mathematical framework for the description of flow-driven oscillators. These oscillators, differently from frequency-driven harmonic systems, are based on countercurrent mass flows and thermal-energy exchange. We describe this class of oscillators through two countercurrent fluids separated by a heated conductive medium. We show how this configuration embeds the essential elements of harmonic oscillators, such as resonance condition, periodic orbits, and quality factor or decay time. The key advantage of recognizing flow-driven systems as oscillators lies in the possibility to engineer them according to the properties of resonant systems and utilize them to control their temperature, maximize the stored energy, or coupling them in networks. We report examples of simple configurations at their resonant condition, enhancing both thermal energy and decay time by factors larger than 10. We finally show two flow-driven oscillators coupled in series, featuring a reconfigurable internal temperature distribution, depending on the selected resonant condition.
Giant photothermoelectric effect in silicon nanoribbon photodetectors
(Springer Nature, 2020) Dai, Wei; Liu, Weikang; Yang, Jian; Xu, Chao; Alabastri, Alessandro; Liu, Chang; Nordlander, Peter; Guan, Zhiqiang; Xu, Hongxing; Laboratory for Nanophotonics
The photothermoelectric (PTE) effect enables efficient harvesting of the energy of photogenerated hot carriers and is a promising choice for high-efficiency photoelectric energy conversion and photodetection. Recently, the PTE effect was reported in low-dimensional nanomaterials, suggesting the possibility of optimizing their energy conversion efficiency. Unfortunately, the PTE effect becomes extremely inefficient in low-dimensional nanomaterials, owing to intrinsic disadvantages, such as low optical absorption and immature fabrication methods. In this study, a giant PTE effect was observed in lightly doped p-type silicon nanoribbons caused by photogenerated hot carriers. The open-circuit photovoltage responsivity of the device was 3-4 orders of magnitude higher than those of previously reported PTE devices. The measured photovoltage responses fit very well with the proposed photothermoelectric multiphysics models. This research proposes an application of the PTE effect and a possible method for utilizing hot carriers in semiconductors to significantly improve their photoelectric conversion efficiency.
Golden Plasmophores with Tunable Photoluminescence and Outstanding Thermal and Photothermal Stability
(Wiley, 2024) Gharib, Mustafa; Yates, A. J.; Sanders, Stephen; Gebauer, Johannes; Graf, Sebastian; Ziefuß, Anna Rosa; Nonappa; Kassier, Günther; Rehbock, Christoph; Barcikowski, Stephan; Weller, Horst; Alabastri, Alessandro; Nordlander, Peter; Parak, Wolfgang J.; Chakraborty, Indranath
Among various hybrid nanomaterials, the combination of plasmonic nanoparticles and fluorophores in a single multifunctional nanoplatform, so-called plasmophores, has attracted significant attention in different fields such as dark field, fluorescence, and photoacoustic imaging, biosensing, photothermal, and photodynamic therapy. Herein, author report a facile and controlled synthesis route of hybrid nanoplatforms composed of fluorescent gold nanoclusters (GNCs) coupled to plasmonic gold nanorods (GNRs) using controlled silica (SiO2) dielectric spacers of different thicknesses from now on referred to as GNR@SiO2@GNC plasmophores. The results show different degrees of plasmon-enhanced fluorescence of the GNCs in their plasmophore hybrid system when placed at different distances from the plasmonic cores of the GNRs. On the other hand, these plasmophores show enhanced thermal stability compared to GNRs@CTAB (CTAB, cetyl trimethyl ammonium bromide). This results also demonstrated that upon annealing at elevated temperatures (800–1000 °C), the GNRs in the plasmophores are more thermally stable and robust than the GNRs@CTAB. More surprisingly, despite the commonly reported very low melting temperature of smaller-size nanocrystals, the GNCs in the plasmophores showed high thermal stability and do not exhibit significant structural changes at elevated temperatures (800–1000 °C).
Hot carrier spatio-temporal inhomogeneities in ultrafast nanophotonics
(IOP Publishing, 2022) Schirato, Andrea; Crotti, Giulia; Zaccaria, Remo Proietti; Alabastri, Alessandro; Valle, Giuseppe Della
Light-induced hot carriers in nanostructures and their corresponding optical nonlinearity have been extensively examined during the last decades. However, nonlinear optical effects dictated by the spatio-temporal evolution of out-of-equilibrium electrons at the nanoscale represent a much more recent research focus. Here we theoretically discuss the role of spatial inhomogeneities that energetic electrons feature across individual nanoantennas in metasurface configuration upon illumination with femtosecond laser pulses. As exemplary cases, we consider two-dimensional geometries of gold meta-atoms having either a high aspect ratio or a tapered cross-section and model their ultrafast optical response. A comparison with numerical results obtained either neglecting or accounting for spatial effects indicates that deep sub-wavelength spatio-temporal transients of carriers may have a significant impact on the dynamics of the all-optically modulated signal, with major quantitative corrections up to predicted changes in sign. Our results present hot-electron local inhomogeneities as an emerging subject with potentially relevant applications in various ultrafast nanophotonic configurations.
Large-Scale Decentralized Solar Desalination: A Blueprint to Make Efficient Day-Long Technologies a Reality
(2023-08-08) Schmid, William; Alabastri, Alessandro
Among potential solutions to global water scarcity, thermal desalination is a flexible choice for water treatment, given its key advantages in robustness and limited salinity dependence. Light can power thermal desalination by dissipating electromagnetic energy into heat. Solar-driven photothermal desalination (SDPD) can lead to decentralized water purification, improving accessibility and reducing the environmental impact over conventional, heavy infrastructure-based desalination practices like reverse osmosis. Unfortunately, today’s best decentralizable SDPD technologies barely surpass 10% of the thermodynamic limit for thermal desalination. Furthermore, there is limited consensus on how to best evaluate and compare the efficiency of diverse solar-driven systems, particularly with respect to their day-long performance under natural, time-varying intensity. Recently, we proposed a generalized approach for achieving efficient, scalable, and day-long SDPD. Instead of optimizing individual components like solar absorbers and evaporators, our approach emphasizes the critical transfers of power underpinning the entire thermal desalination process. In particular, the minimization of environmental losses and maximization of heat recovery depend on each other, and their combination is paramount in bolstering the performance of real-world practical systems. Guided by our approach, we have determined that SDPD systems of a specific size and input salinity operate most efficiently at a specific optimal input power, a previously understudied fact with major implications on the day-long operation of modular networks of individual systems. By focusing on optimizing system-wide thermal energy recovery, loss mitigation and exploiting dynamic energy recovery schemes that can be tuned adaptively for time-varying input power, highly efficient, cost-effective systems can be designed to best take advantage of available light.
Nanoporous Metals: From Plasmonic Properties to Applications in Enhanced Spectroscopy and Photocatalysis
(American Chemical Society, 2021) Koya, Alemayehu Nana; Zhu, Xiangchao; Ohannesian, Nareg; Yanik, A. Ali; Alabastri, Alessandro; Proietti Zaccaria, Remo; Krahne, Roman; Shih, Wei-Chuan; Garoli, Denis
The field of plasmonics is capable of enabling interesting applications in different wavelength ranges, spanning from the ultraviolet up to the infrared. The choice of plasmonic material and how the material is nanostructured has significant implications for ultimate performance of any plasmonic device. Artificially designed nanoporous metals (NPMs) have interesting material properties including large specific surface area, distinctive optical properties, high electrical conductivity, and reduced stiffness, implying their potentials for many applications. This paper reviews the wide range of available nanoporous metals (such as Au, Ag, Cu, Al, Mg, and Pt), mainly focusing on their properties as plasmonic materials. While extensive reports on the use and characterization of NPMs exist, a detailed discussion on their connection with surface plasmons and enhanced spectroscopies as well as photocatalysis is missing. Here, we report on different metals investigated, from the most used nanoporous gold to mixed metal compounds, and discuss each of these plasmonic materials’ suitability for a range of structural design and applications. Finally, we discuss the potentials and limitations of the traditional and alternative plasmonic materials for applications in enhanced spectroscopy and photocatalysis.
Nanoporous Titanium Oxynitride Nanotube Metamaterials with Deep Subwavelength Heat Dissipation for Perfect Solar Absorption
(American Chemical Society, 2023) Afshar, Morteza; Schirato, Andrea; Mascaretti, Luca; Hejazi, S. M. Hossein; Shahrezaei, Mahdi; Della Valle, Giuseppe; Fornasiero, Paolo; Kment, Štěpán; Alabastri, Alessandro; Naldoni, Alberto
We report a quasi-unitary broadband absorption over the ultraviolet–visible–near-infrared range in spaced high aspect ratio, nanoporous titanium oxynitride nanotubes, an ideal platform for several photothermal applications. We explain such an efficient light–heat conversion in terms of localized field distribution and heat dissipation within the nanopores, whose sparsity can be controlled during fabrication. The extremely large heat dissipation could not be explained in terms of effective medium theories, which are typically used to describe small geometrical features associated with relatively large optical structures. A fabrication-process-inspired numerical model was developed to describe a realistic space-dependent electric permittivity distribution within the nanotubes. The resulting abrupt optical discontinuities favor electromagnetic dissipation in the deep sub-wavelength domains generated and can explain the large broadband absorption measured in samples with different porosities. The potential application of porous titanium oxynitride nanotubes as solar absorbers was explored by photothermal experiments under moderately concentrated white light (1–12 Suns). These findings suggest potential interest in realizing solar-thermal devices based on such simple and scalable metamaterials.
Photothermal Emission and Absorption in Carbon Materials
(2023-07-27) Jerome, Bryant Beau; Alabastri, Alessandro
Carbon-based materials of many varieties have long been known to act as broadband absorbers, making them useful for thermal radiation control and photothermal applications, depending on their optical and thermophysical properties. In this work, we explore the potential applications of carbon-based materials as hyperbolic thermal emitters and highly localized photothermal heat sources, showing the promise of these materials to advance thermal and optical systems across the nano- and macro-scale. The first chapter of this thesis is dedicated to exploring aligned carbon nanotube films as hyperbolic thermal emitters. Due to an extremely anisotropic optical dispersion, carbon nanotubes can display peculiar light-matter interaction properties. The hyperbolic dispersion of aligned carbon nanotubes in the infrared makes them excellent candidates for thermal emitter applications; however, there is significant difficulty in coupling photons from the bulk of the carbon nanotube film to free space, especially for macroscopic film thicknesses. Using systematic Finite Element Method calculations, we propose a novel grating scheme consisting of a deep etch cut directly into a CNT film. This allows bulk plasmon polaritons to couple to free space across the thickness of the etched grating, suggesting a strategy for the emitters for macro-scale applications. The second chapter is dedicated to using carbon black nanoparticles to generate a localized heat source from ambient sunlight for solar thermal desalination. The majority of this chapter is dedicated to using Finite Element Method calculations to improve the efficiency at which a thermal desalination system exploits the heat source provided by carbon black nanoparticles. We find that short, intense heating regions separated from the evaporating region can result in a large, power-independent efficiency for an optimized desalination system. Cost-effective carbon black nanoparticles are uniquely positioned to serve as a heat source in these systems, demonstrating their usefulness in general photothermal applications.
Plasmonic nanoparticle-based epoxy photocuring: A deeper look
(Elsevier, 2019) Roberts, Adam T.; Yang, Jian; Reish, Matthew E.; Alabastri, Alessandro; Halas, Naomi J.; Nordlander, Peter; Everitt, Henry O.
Many epoxyﾠadhesivesﾠrequire high temperatures to bondﾠcomposite materials. However, oven heating severely restricts what may be attached or enclosed within composite material-based structures and greatly limits the possibilities for repair. Inspired by initial reports of photothermal epoxy curing usingﾠplasmonicnanoparticles, we examine how laser-illuminated Au nanoparticles embedded within high-temperature epoxy films convert the conventional thermal curing process into a photothermally driven one. Our theoretical investigations reveal that plasmonic nanoparticle-based epoxy photocuring proceeds through a four-stage process: a rapid, plasmon-induced temperature increase, a slow localizedﾠinitializationﾠof the curing chemistry that increases theﾠoptical absorptionﾠof the epoxy film, a subsequent temperature increase as the epoxy absorbs theﾠlaser radiationﾠdirectly, and a final stage that completes theﾠchemical transformationﾠof the epoxy film to its cured state. Our experimental studies validate this model, and also reveal that highly local photocuring can create a stronger bond between composite materials than thermal curing without nanoparticles, at times even stronger than the composite material itself, substantially reducing the time needed for the curing process. Our findings support key advances in our understanding of this approach to the rapid, highly efficient bonding and repair of composite materials.
Polarized evanescent waves reveal trochoidal dichroism
(National Academy of Sciences, 2020) McCarthy, Lauren A.; Smith, Kyle W.; Lan, Xiang; Jebeli, Seyyed Ali Hosseini; Bursi, Luca; Alabastri, Alessandro; Chang, Wei-Shun; Nordlander, Peter; Link, Stephan; Laboratory for Nanoscale Spectroscopic Imaging at Rice; Laboratory for Nanophotonics
Matter’s sensitivity to light polarization is characterized by linear and circular polarization effects, corresponding to the system’s anisotropy and handedness, respectively. Recent investigations into the near-field properties of evanescent waves have revealed polarization states with out-of-phase transverse and longitudinal oscillations, resulting in trochoidal, or cartwheeling, field motion. Here, we demonstrate matter’s inherent sensitivity to the direction of the trochoidal field and name this property trochoidal dichroism. We observe trochoidal dichroism in the differential excitation of bonding and antibonding plasmon modes for a system composed of two coupled dipole scatterers. Trochoidal dichroism constitutes the observation of a geometric basis for polarization sensitivity that fundamentally differs from linear and circular dichroism. It could also be used to characterize molecular systems, such as certain light-harvesting antennas, with cartwheeling charge motion upon excitation.
Solar thermal desalination as a nonlinear optical process
(National Academy of Sciences, 2019) Dongare, Pratiksha D.; Alabastri, Alessandro; Neumann, Oara; Nordlander, Peter; Halas, Naomi J.; Laboratory for Nanophotonics; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment
The ever-increasing global need for potable water requires practical, sustainable approaches for purifying abundant alternative sources such as seawater, high-salinity processed water, or underground reservoirs. Evaporation-based solutions are of particular interest for treating high salinity water, since conventional methods such as reverse osmosis have increasing energy requirements for higher concentrations of dissolved minerals. Demonstration of efficient water evaporation with heat localization in nanoparticle solutions under solar illumination has led to the recent rapid development of sustainable, solar-driven distillation methods. Given the amount of solar energy available per square meter at the Earth’s surface, however, it is important to utilize these incident photons as efficiently as possible to maximize clean water output. Here we show that merely focusing incident sunlight into small “hot spots” on a photothermally active desalination membrane dramatically increases––by more than 50%––the flux of distilled water. This large boost in efficiency results from the nearly exponential dependence of water vapor saturation pressure on temperature, and therefore on incident light intensity. Exploiting this inherent but previously unrecognized optical nonlinearity should enable the design of substantially higher-throughput solar thermal desalination methods. This property provides a mechanism capable of enhancing a far wider range of photothermally driven processes with supralinear intensity dependence, such as light-driven chemical reactions and separation methods.
Synthesis of plasmonic gold nanoparticles on soft materials for biomedical applications
(Elsevier, 2023) Granata, Federica; Pirillo, Noemi; Alabastri, Alessandro; Schirato, Andrea; Bruno, Luigi; Costa, Roberta; Malara, Natalia; Onesto, Valentina; Coluccio, Maria Laura; Iodice, Mario; Coppola, Giuseppe; Gentile, Francesco
Plasmonic metal nanomaterials are usually supported by rigid substrates, typically made of silicon or glass. Recently, there has been growing interest in developing soft plasmonic devices. Such devices are low weight, low cost, exhibit elevated flexibility and improved mechanical properties. Moreover, they maintain the features of conventional nano-optic structures, such as the ability to enhance the local electromagnetic field. On account of these characteristics, they show promise as efficient biosensors in biological, medical, and bio-engineering applications. Here, we demonstrate the fabrication of soft polydimethylsiloxane (PDMS) plasmonic devices. Using a combination of techniques, including electroless deposition, we patterned thin membranes of PDMS with arrays of gold nanoparticle clusters. Resulting devices show regular patterns of gold nanoparticles extending over several hundreds of microns and are moderately hydrophilic, with a contact angle of about 80°. At the nanoscale, scanning electron and atomic force microscopy of samples reveal an average particle size of ∼50 nm. The nanoscopic size of the particles, along with their random distribution in a cluster, promotes the enhancement of electromagnetic fields, evidenced by numerical simulations and experiments. Mechanical characterization and the stress-strain relationship indicate that the device has a stiffness of 2.8 MPa. In biological immunoassay tests, the device correctly identified and detected anti-human immunoglobulins G (IgG) in solution with a concentration of 25 μg/ml.
Utilizing the broad electromagnetic spectrum and unique nanoscale properties for chemical-free water treatment
(Elsevier, 2021) Westerhoff, Paul; Alvarez, Pedro J.J.; Kim, Jaehong; Li, Qilin; Alabastri, Alessandro; Halas, Naomi J.; Villagran, Dino; Zimmerman, Julie; Wong, Michael S.; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT)
Clean water is critical for drinking, industrial processes, and aquatic organisms. Existing water treatment and infrastructure are chemically intensive and based on nearly century-old technologies that fail to meet modern large and decentralized communities. The next-generation of water processes can transition from outdated technologies by utilizing nanomaterials to harness energy from across the electromagnetic spectrum, enabling electrified and solar-based technologies. The last decade was marked by tremendous improvements in nanomaterial design, synthesis, characterization, and assessment of material properties. Realizing the benefits of these advances requires placing greater attention on embedding nanomaterials onto and into surfaces within reactors and applying external energy sources. This will allow nanomaterial-based processes to replace Victorian-aged, chemical intensive water treatment technologies.

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