Center for Nanoscience and Nanotechnology

Superhydrophobic surfaces are of high importance for generating self-cleaning surfaces that can also prevent corrosion, biofouling, fogging, and icing. Current superhydrophobic surfaces, often based on fluorinated compounds, pose environmental concerns, have high fabrication costs, and exhibit low stability. Herein, we designed fluorine-free amino acid-based nanoparticles (SiO2-Phe-Cbz NPs) to fabricate a superhydrophobic coating on elastomers that can be utilized in soft electroadhesive (EA) grippers. The synthesized SiO2-Phe-Cbz NPs are spherical with a diameter of ∼100 nm. Importantly, the synthesized NPs are non-toxic to mammalian cells. The SiO2-Phe-Cbz coating is achieved by spray-coating resulting in a water contact angle of ∼160° and a sliding angle of ∼1°. Notably, the SiO2-Phe-Cbz superhydrophobic coating presents high stability and self-cleaning properties. Furthermore, the coating …

In this work, we present a free-space transmissive light amplitude modulator based on thin-film lithium niobate on an insulator platform with an indium tin oxide meta-grating. The design leverages guided mode resonances induced by the transparent conductive oxide layer, enabling efficient electrooptical modulation in the near-infrared region. By integrating transparent conductive oxide both as electrical contact and as the resonating structure, the device eliminates the need for complex alignment during fabrication and minimizes optical losses associated with metallic contacts. We experimentally demonstrate that the device achieves a fundamental mode resonance at 968.5 nm with a quality factor of 440. The electrooptical tuning efficiency is thoroughly investigated across different modes using measurements and simulations. A notable resonance shift of 0.38 nm is observed for the fundamental mode under a ±10 …

Nano-patterned magnetic materials have opened new venues on the investigation of strongly correlated phenomena including artificial spin-ice systems, geometric frustration, magnetic monopoles, for technologically important applications such as reconfigurable ferromagnetism. With the advent of atomically thin two-dimensional (2D) van der Waals (vdW) magnets a pertinent question is whether such compounds could make their way into this realm where interactions can be tailored so that unconventional states of matter could be assessed. Here we show that square islands of CrGeTe3 vdW ferromagnets distributed in a grid manifest antiferromagnetic correlations, essential to enable frustration resulting in an artificial spin-ice. By using a combination of SQUID-on-tip microscopy, focused ion beam lithography, and atomistic spin dynamic simulations, we show that pristine, isolated CGT flakes as small as 150*150*60 nm3 have tunable dipole-dipole interactions, which can be precisely controlled by their lateral spacing. There is a crossover between non-interacting islands and significant inter-island anticorrelation depending how they are spatially distributed allowing the creation of complex magnetic patterns not observable at the isolated flakes. Our findings suggest that the cross-talk between the nano-patterned magnets can be explored in the generation of even more complex spin configurations where exotic interactions may be manipulated in an unprecedent way.

Interactions of electron spins with rotational degrees of freedom during collisions or with external fields are fundamental processes that limit the coherence time of spin gases. We experimentally study the decoherence of warm cesium spins dominated by spin rotation-interaction during binary collisions with N molecules or by absorption of near-resonant light. We report an order of magnitude suppression of the spin decoherence rate by either of those processes at low magnetic fields. We find that the excess decoherence at higher magnetic fields originates from an asynchronous Larmor precession, which is a mechanism that universally affects all alkali atoms, and can yet be suppressed at low magnetic-fields. This work extends the widely-used regime of Spin-Exchange Relaxation Free (SERF), which provides protection from decoherence by random spin-conservative processes, now for random processes which do not conserve but rather destruct electron spins.

Photonic technologies continue to drive the quest for new optical materials with unprecedented responses. A major frontier in this field is the exploration of nonlocal (spatially dispersive) materials, going beyond the local, wavevector-independent assumption traditionally made in optical material modeling. On one end, the growing interest in plasmonic, polaritonic and quantum materials has revealed naturally occurring nonlocalities, emphasizing the need for more accurate models to predict and design their optical responses. This has major implications also for topological, nonreciprocal, and time-varying systems based on these material platforms. Beyond natural materials, artificially structured materials--metamaterials and metasurfaces--can provide even stronger and engineered nonlocal effects, emerging from long-range interactions or multipolar effects. This is a rapidly expanding area in the field of photonic metamaterials, with open frontiers yet to be explored. In the case of metasurfaces, in particular, nonlocality engineering has become a powerful tool for designing strongly wavevector-dependent responses, enabling enhanced wavefront control, spatial compression, multifunctional devices, and wave-based computing. Furthermore, nonlocality and related concepts play a critical role in defining the ultimate limits of what is possible in optics, photonics, and wave physics. This Roadmap aims to survey the most exciting developments in nonlocal photonic materials, highlight new opportunities and open challenges, and chart new pathways that will drive this emerging field forward--toward new scientific discoveries and technological …

The formation of ice and frost on surfaces poses significant challenges to aviation, crop protection, organ preservation, and other fields. This paper presents the formation of sustainable antifreeze coating by the self-assembly of short peptides. The peptide design is inspired by and combines different elements from distinct natural proteins: (i) a sequence of amino acids from an antifreeze protein and (ii) the amino acids 3,4-dihydroxyphenylalanine (DOPA) and lysine from mussel adhesion proteins that anchor the peptide to a surface. The peptide, termed AFPep1, incorporates the repetitive ice-binding motif found in the antifreeze protein of the longhorn beetle (Rhagium inquisitor). Surfaces coated with the peptide exhibited antifreeze activity with a delay of the initial freezing of 5 °C degrees compared to a bare surface. Furthermore, AFPep1 exhibited relatively effective ice recrystallization inhibition (IRI) activity in …

Quantum dots (QDs) are prominent nanometric light emitters, featuring quantum behavior due to the quantum confinement effect. This effect is responsible for the size‐dependent optoelectronic properties of QDs, which makes them a versatile building block for various applications. Moreover, the bright emission of QDs and narrow spectral lines make them ideal for display applications. However, QDs also undergo nonradiative processes that can impair their functionality in display devices. This chapter delves into the physics and photophysics of QDs. It discusses quantum confinement and size and shape effects, heterostructures and surface effects, the absorption and emission spectra, charge dynamics, stability, and collective effects, aiming to shed light on the intricate nature of the QDs' photophysics.

Spin-exchange relaxation-free magnetometers based on dense ensembles of alkali-metal spins are precision quantum sensors that hold the record of measured and projected sensitivity to magnetic fields, in the microgauss to milligauss range. At geomagnetic fields however, these sensors quickly lose their magnetic sensitivity due to spin decoherence by random spin-exchange collisions. Here we discover that atoms with nuclear spin can operate in the spin-exchange relaxation-free regime even at high magnetic field. We counterintuitively show that frequent collisions between a dense and optically inaccessible gas with another optically accessible spin gas () improve the fundamental magnetic sensitivity of the latter. We analyze the performance of a dual-species potassium and atomic hydrogen magnetometer and project a fundamental sensitivity of about at geomagnetic fields for …

Continuous-Wave Terahertz (CW-THz) phase and amplitude imaging provides valuable insights into the interaction between THz waves and matter, particularly in low-absorption materials. This information is also essential for enhancing CW-THz beam profiling, a critical aspect in the design of free-space THz devices. Hereby, we introduce a single-pixel THz amplitude and phase imaging technique based on frequency scanning and fringe analysis, incorporated into a straightforward experimental setup. We validate the usefulness of the proposed approach by demonstrating two representative case studies. The first is a 3-D measurement of the amplitude and phase profile of a THz wave that is transmitted through a 3-D printed metalens. The second is beam profiling of a THz beam emitted from a photomixer antenna. In both cases, our results are in excellent agreement with previous predictions and validate the …

Metalenses have become ubiquitous in academic research and have begun to make their transition to industry. However, chromatic aberration still greatly limits the applications of metalenses. Achieving a wide field-of-view (FOV) is another challenge that has been dealt with successfully by using a removed stop, but when combined with broadband spectrum, lateral chromatic aberration severely limits performance. In this paper we tackle this grand challenge and present a comprehensive design methodology for a simultaneously wide-FOV and achromatic metalens which is inspired by the human visual system. As a design example, we present a metalens operating in the near infrared (NIR), with 10% relative spectral bandwidth (807-893nm), focal length of 5mm, F/5, and FOV of +/-20 degrees. In particular, we show how to optimize the stop position, and correct the lateral chromatic aberration, both of which have not been reported in the past. In addition, we evaluate the performance of the metalens using accurate performance metrics, and demonstrate the improvement compared to a chromatic metalens. Our approach paves the way for the design of wide FOV metalenses that can operate over a relatively large bandwidth, effectively contributing to the widespread implementation of metalens science and technology.

This review atempts to summarize my three decades-long involvement in, and contribution to, the design, construction and testing of bioluminescent microbial sensor strains (bioreporters). With the understanding that such a document cannot be completely free of bias, the review focuses on studies from my own lab only, with almost no coverage of the parallel progress made by others in similar fields. This admitedly subjective approach by no way detracts from the achievements of countless excellent researchers who are not mentioned here, and whose contributions to the field are at least as important as that of my own. The review covers basic aspects of microbial sensor design, and then progresses to describe approaches to performance improvement of sensor strains aimed at the detection of either specific chemicals, groups of chemicals sharing similar characteristics, or global effects, such as toxicity and …

With the increasing consumption of nanomaterials in a variety of applications, our environment becomes more and more exposed to different kinds of (possibly toxic) nanomaterials having variable sizes and shapes, raising up the requirement to sense and monitor the presence of nanomaterials. Here, we propose and demonstrate a porous-silicon based optical sensing platform, capable of sensing nanoparticles of a given distribution of sizes and shapes, but independent of their chemical, mechanical, or electrical properties. A white light optical interference technique has been utilized to transduce nanoparticles trapped in the porous matrix into an optical signal. We have found an unusual optical sensing response that substantially increases the sensing bandwidth of the porous-silicon based optical sensor, which follows a Hill-equation type behavior that is characterized by a logarithmic response at low …

This review attempts to summarize my three decades-long involvement in, and contribution to, the design, construction and testing of bioluminescent microbial sensor strains (bioreporters). With the understanding that such a document cannot be completely free of bias, the review focuses on studies from my own lab only, with almost no coverage of the parallel progress made by others in similar fields. This admittedly subjective approach by no way detracts from the achievements of countless excellent researchers who are not mentioned here, and whose contributions to the field are at least as important as that of my own. The review covers basic aspects of microbial sensor design, and then progresses to describe approaches to performance improvement of sensor strains aimed at the detection of either specific chemicals, groups of chemicals sharing similar characteristics, or global effects, such as toxicity and …

Continuous-Wave Terahertz (CW-THz) phase and amplitude imaging provides valuable insights into the interaction between THz waves and matter, particularly in low-absorption materials. This information is also essential for enhancing CW-THz beam profiling, a critical aspect in the design of free-space THz devices. Hereby, we introduce a single-pixel THz amplitude and phase imaging technique based on frequency scanning and fringe analysis, incorporated into a straightforward experimental setup. We validate the usefulness of the proposed approach by demonstrating two representative case studies. The first is a 3-D measurement of the amplitude and phase profile of a THz wave that is transmitted through a 3-D printed metalens. The second is beam profiling of a THz beam emitted from a photomixer antenna. In both cases, our results are in excellent agreement with previous predictions and validate the …

Superhydrophobic surfaces are of high importance for generating self-cleaning surfaces that can also prevent corrosion, biofouling, fogging, and icing. Current superhydrophobic surfaces, often based on fluorinated compounds, pose environmental concerns, have high fabrication costs, and exhibit low stability. Herein, we design fluorine-free amino acid-based nanoparticles (SiO2-Phe-Cbz NPs) to fabricate a superhydrophobic coating on elastomers that can be utilized in soft electroadhesive (EA) grippers. The synthesized SiO2-Phe-Cbz NPs are spherical with a diameter of ∼100 nm. Importantly, the synthesized NPs are non-toxic to mammalian cells. The SiO2-Phe-Cbz coating is achieved by spray-coating resulting in a water contact angle of ∼160° and a sliding angle of ∼1°. Notably, the SiO2-Phe-Cbz superhydrophobic coating presents high stability and self-cleaning properties. Furthermore, the coating does …

The increasing interest in protein and peptide coacervates is accompanied by the development of various applications, from drug delivery to biosensor preparation. However, the impact of peptide end groups and charges on the coacervation remains unclear. For this purpose, we designed four peptide derivatives with varying end groups and net charges. These inherently fluorescent peptides readily formed coacervates in solution or during evaporation. The ability to control the coacervation process, the coacervate’s appearance, and the encapsulation capabilities were thoroughly investigated. The coacervates displayed significant antioxidant properties, protecting the encapsulated material. Additionally, control of the deposition of the coacervates on surfaces was achieved. These abilities highlight the potential of these coacervates in biotechnological applications, including biosensor development and delivery of …

Semiconductor–metal hybrid nanoparticles (HNPs) are promising materials for photocatalytic applications, such as water splitting for green hydrogen generation. While most studies have focused on Cd containing HNPs, the realization of actual applications will require environmentally compatible systems. Using heavy-metal free ZnSe-Au HNPs as a model, we investigate the dependence of their functionality and efficiency on the cocatalyst metal domain characteristics ranging from the single-atom catalyst (SAC) regime to metal-tipped systems. The SAC regime was achieved via the deposition of individual atomic cocatalysts on the semiconductor nanocrystals in solution. Utilizing a combination of electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy, we established the presence of single Au atoms on the ZnSe nanorod surface. Upon increased Au concentration, this transitions …

Bioinspired piezoelectric amino acids and peptides are attracting attention due to their designable sequences, versatile structures, low cost, and biodegradability. However, it remains a challenge to design amino acids and peptides with high piezoelectricity. Herein, a high piezoelectric amino acid by simple fluorination in its side chain is presented. The three phenylalanine derivatives are designed: Cbz‐Phe, Cbz‐Phe(4F), and Cbz‐pentafluoro‐Phe. The effect of fluorination on self‐assembly and piezoelectricity is investigated. Cbz‐Phe(4F) can self‐assemble into crystals with a C2 space group, while Cbz‐Phe and Cbz‐pentafluoro‐Phe form aggregated self‐assemblies. Moreover, Cbz‐Phe(4F) crystals exhibit a remarkably higher piezoelectric coefficient (d33eff$d_{\ 33}^{\ eff}$) of ≈17.9 pm V−1 than Cbz‐Phe and Cbz‐pentafluoro‐Phe. When fabricated as a piezoelectric nanogenerator, it generates an open …

Semiconductor–metal hybrid nanoparticles (HNPs) are promising materials for photocatalytic applications, such as water splitting for green hydrogen generation. While most studies have focused on Cd containing HNPs, the realization of actual applications will require environmentally compatible systems. Using heavy-metal free ZnSe-Au HNPs as a model, we investigate the dependence of their functionality and efficiency on the cocatalyst metal domain characteristics ranging from the single-atom catalyst (SAC) regime to metal-tipped systems. The SAC regime was achieved via the deposition of individual atomic cocatalysts on the semiconductor nanocrystals in solution. Utilizing a combination of electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy, we established the presence of single Au atoms on the ZnSe nanorod surface. Upon increased Au concentration, this transitions …

Bioinspired piezoelectric amino acids and peptides are attracting attention due to their designable sequences, versatile structures, low cost, and biodegradability. However, it remains a challenge to design amino acids and peptides with high piezoelectricity. Herein, a high piezoelectric amino acid by simple fluorination in its side chain is presented. The three phenylalanine derivatives are designed: Cbz‐Phe, Cbz‐Phe(4F), and Cbz‐pentafluoro‐Phe. The effect of fluorination on self‐assembly and piezoelectricity is investigated. Cbz‐Phe(4F) can self‐assemble into crystals with a C2 space group, while Cbz‐Phe and Cbz‐pentafluoro‐Phe form aggregated self‐assemblies. Moreover, Cbz‐Phe(4F) crystals exhibit a remarkably higher piezoelectric coefficient (d33eff$d_{\ 33}^{\ eff}$) of ≈17.9 pm V−1 than Cbz‐Phe and Cbz‐pentafluoro‐Phe. When fabricated as a piezoelectric nanogenerator, it generates an open …