BINA

Carbon dots (CDs) are a novel type of carbon-based nanomaterial that has gained considerable attention for their unique optical properties, including tunable fluorescence, stability against photobleaching and photoblinking, and strong fluorescence, which is attributed to a large number of organic functional groups (amino groups, hydroxyl, ketonic, ester, and carboxyl groups, etc.). In addition, they also demonstrate high stability and electron mobility. This article reviews the topic of doped CDs with organic and inorganic atoms and molecules. Such doping leads to their functionalization to obtain desired physical and chemical properties for biomedical applications. We have mainly highlighted modification techniques, including doping, polymer capping, surface functionalization, nanocomposite and core-shell structures, which are aimed at their applications to the biomedical field, such as bioimaging, bio-sensor applications, neuron tissue engineering, drug delivery and cancer therapy. Finally, we discuss the key challenges to be addressed, the future directions of research, and the possibilities of a complete hybrid format of CD-based materials.

Pt–Ni polyhedral nanoparticles (NPs) are extensively studied as electrocatalysts, mainly for oxygen reduction reaction (ORR), but they display a poor activity for the oxygen evolution reaction (OER). Here, ultralow platinum Pt@Ni@Pt core–bishell nanorods were designed (less than 1 wt % of Pt), synthesized, and characterized to yield bifunctional electrocatalysts with high efficiency toward ORR and OER in alkaline media. Ultralow platinum Pt@Ni@Pt core–bishell nanorods achieve an unprecedented (for a Pt-based catalyst) overpotential of 0.29 V at 10 mA cm–2 and current density of 162 mA μg–1Pt at 1.6 V (vs RHE) for the OER, while still maintaining a very decent value of 0.32 A mg–1Pt at 0.85 V for the ORR. These values outperform the standard Pt catalyst for the ORR and the Ni catalyst for the OER, using less than 1 wt % Pt. We describe the two-step synthesis of the Pt@Ni@Pt nanorods, demonstrating the …

Ultra-thin hydrophobic capping layers of two-dimensional (2D) onto three-dimensional (3D) metal halide perovskites (HaPs) are an attractive strategy for preventing ambient-induced degradation and minimizing interfacial non-idealities of 3D HaPs. However, it is not obvious in how far the unusual 3D HaP lattice dynamics affect 2D-on-3D HaP composites’ stability, especially at their interface, an issue important for devices made with such composites. Using low electron–fluence, four-dimensional scanning transmission electron microscopy and nanobeam electron diffraction, we show formation of the 2D (n = 1) phase on top of 3D perovskite, using focused-ion beam-prepared cross-sections, under conditions that minimize radiation damage. The 2D-on-3D HaP composites were prepared by controlled gas-phase surface cation exchange of 3D MAPbI3 films to form A2PbI4, where A = (fluoro-)phenyl-ethyl-ammonium …

Thin-film lithium niobate has shown promise for scalable applications ranging from single-photon sources to high-bandwidth data communication systems.Realization of the next generation high-performance classical and quantum devices, however, requires much lower optical losses than the current state of the art resonator (Q-factor of 10 million). Yet material limitations of ion-sliced thin film lithium niobate have not been explored, and therefore it is unclear how high the quality factor can be achieved in this platform. Here, using our newly developed characterization method, we find out that the material limited quality factor of thin film lithium niobate photonic platform can be improved using post-fabrication annealing, and can be as high as Q~1.6×108 at telecommunication wavelengths, corresponding to a propagation loss of ~0.2 dB/m.

Highly reflective crystals of the nucleotide base guanine are widely distributed in animal coloration and visual systems. Organisms precisely control the morphology and organization of the crystals to optimize different optical effects, but little is known about how this is achieved. Here we examine a fundamental question that has remained unanswered after over 100 years of research on guanine: what are the crystals made of? Using solution-state and solid-state chemical techniques coupled with structural analysis by powder XRD and solid-state NMR, we compare the purine compositions and the structures of seven biogenic guanine crystals with different crystal morphologies, testing the hypothesis that intracrystalline dopants influence the crystal shape. We find that biogenic “guanine” crystals are not pure crystals but molecular alloys (aka solid solutions and mixed crystals) of guanine, hypoxanthine, and …

Bone is a fascinating biomaterial comprised mostly of type-I collagen fibers as an organic phase, apatite as an inorganic phase, with water molecules residing at the interfaces between these phases. They are hierarchically organized with minor constituents such as non-collagenous proteins, citrate ions and glycosaminoglycans into a composite structure that is mechanically durable yet contains enough porosity to accommodate cells and blood vessels. The nanometer scale organization of the collagen fibrous structure and the mineral constituents in bone were recently extensively scrutinized. However, molecular details at the lowest hierarchical level still need to be unraveled to better understand the exact atomic-level arrangement of all these important components in the context of the integral structure of the bone. In this report, we unfold some of the molecular characteristics differentiating between two load …

The study of recurrences and revivals in quantum systems has attracted a great deal of interest because of its importance in the control of quantum systems and its potential use in developing new technologies. In this paper, we introduce a protocol to induce full-state revivals in a huge class of quantum walks on a d-dimensional lattice governed by a c-dimensional coin system. The protocol requires two repeated interventions in the coin degree of freedom. We also present a characterization of the walks that admit such a protocol. Moreover, we modify the quantity known as the Pólya number, typically used in the study of recurrences in classical random walks and quantum walks, to create a witness of the first revival of the walk.

Catalyst poisoning and leaching is a problem faced in almost all catalyst applications. A specific technology where catalyst poisoning and leaching are a major concern is the hydrogen bromine redox flow battery (H 2–B r 2 RFB), one of the most promising energy storage technologies. However, it is currently hindered through degradation of the hydrogen oxidation/evolution catalyst, caused by B r−/B r 3− which have crossed the membrane. To prevent this degradation, Pt nanoparticles were synthesized inside 2 nm single-walled carbon nanotubes (SWCNTs). Electrochemical and spectroscopic techniques show that the Pt@ SWCNT has a vastly improved stability and higher mass activity over a commercial 50% Pt/C catalyst. Density functional theory (DFT) calculations show that the stability results from the selective diffusion of H 2 and H+ over the B r− and B r 3− species through the SWCNT to the Pt catalyst …

We demonstrate a simple and robust high-resolution ghost spectroscopy approach for x-ray and extreme ultraviolet absorption spectroscopy at free-electron laser sources. Our approach requires an on-line spectrometer before the sample and a downstream bucket detector. We use this method to measure the absorption spectrum of silicon, silicon carbide and silicon nitride membranes in the vicinity of the silicon L2,3-edge. We show that ghost spectroscopy allows the high-resolution reconstruction of the sample spectral response using a coarse energy scan with self-amplified spontaneous emission radiation. For the conditions of our experiment the energy resolution of the ghost-spectroscopy reconstruction is higher than the energy resolution reached by scanning the energy range by narrow spectral bandwidth radiation produced by the seeded free-electron laser. When we set the photon energy resolution of the ghost spectroscopy to be equal to the resolution of the measurement with the seeded radiation, the measurement time with the ghost spectroscopy method is shorter than scanning the photon energy with seeded radiation. The exact conditions for which ghost spectroscopy can provide higher resolution at shorter times than measurement with narrow band scans depend on the details of the measurements and on the properties of the samples and should be addressed in future studies.

Supplement 1 - A comprehensive theoretical treatment of quasi-static optical parametric amplification in the frequency domain, with an example waveguide design.

Conducting polymers, mainly polyaniline (PANI) and polypyrrole (PPY) with positive charges bind to the negatively charged bacterial membrane to interfere with bacterial activities. After this initial electrostatic adherence, the conducting polymers might partially penetrate the bacterial membrane and interact with other intracellular biomolecules. Conducting polymers can form polymer composites with metal, metal oxides, and nanoscale carbon materials as a new class of antimicrobial agents with enhanced antimicrobial properties. The accumulation of elevated oxygen reactive species (ROS) from composites of polymers-metal nanoparticles has harmful effects and induces cell death. Among such ROS, the hydroxyl radical with one unpaired electron in the structure is most effective as it can oxidize any bacterial biomolecules, leading to cell death. Future endeavors should focus on the combination of conducting polymers and their composites with antibiotics, small peptides, and natural molecules with antimicrobial properties. Such arsenals with low cytotoxicity are expected to eradicate the ESKAPE pathogens: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.

The performance of SwissSPAD2 (SS2), a large scale, widefield time-gated CMOS SPAD imager developed for fluorescence lifetime imaging, has recently been described in the context of visible range and fluorescence lifetime imaging microscopy (FLIM) of dyes with lifetimes in the 2.5–4 ns range. Here, we explore its capabilities in the NIR regime relevant for small animal imaging, where its sensitivity is lower and typical NIR fluorescent dye lifetimes are much shorter (1 ns or less). We carry out this study in a simple macroscopic imaging setup based on a compact NIR picosecond pulsed laser, an engineered diffuser-based illumination optics, and NIR optimized imaging lens suitable for well-plate or small animal imaging. Because laser repetition rates can vary between models, but the synchronization signal frequency accepted by SS2 is fixed to 20 MHz, we first checked that a simple frequency-division scheme …

Liposomes are a promising drug delivery system, owing to their biocompatibility and ability to efficiently encapsulate and protect a wide range of molecules for medical applications. Active targeting of the liposomes is typically performed by surface modification, which enables delivery of the liposomes to a specific target tissue. Tumor cells are characterized by high glucose demand and high metabolic activity, because of the increased requirement of energy to feed uncontrolled proliferation. Taking advantage of the increased glucose uptake by cancer cells, we developed a glucose-labeled liposome, which is tumor-targeted - both by recognition of over-expressed glucose transporters on tumor cells, and by the unique characteristics of tumor vasculature that allow greater accumulation of nanoparticles. In this study, glucosecoated liposome uptake was evaluated in different types of cancer cells, both quantitatively …

RNA editing by adenosine deaminases changes the information encoded in the mRNA from its genomic blueprint. Editing of protein-coding sequences can introduce novel, functionally distinct, protein isoforms and diversify the proteome. The functional importance of a few recoding sites has been appreciated for decades. However, systematic methods to uncover these sites perform poorly, and the full repertoire of recoding in human and other mammals is unknown. Here we present a new detection approach, and analyze 9125 GTEx RNA-seq samples, to produce a highly-accurate atlas of 1517 editing sites within the coding region and their editing levels across human tissues. Single-cell RNA-seq data shows protein recoding contributes to the variability across cell subpopulations. Most highly edited sites are evolutionary conserved in non-primate mammals, attesting for adaptation. This comprehensive set can …

We present a study of various compositions of the chalcogenide family used for static and active metasurfaces. We start with large area CVD grown amorphous spherical Selenium nanoparticles on various substrates and show that their Mie-resonant response spans the entire mid-infrared (MIR) range. By coupling Se Mie-resonators to ENZ substrates we demonstrate an order of magnitude increase in quality factor. Next, we investigate topological insulators Bi2Se3 and Bi2Te3 metasurfaces. We study the optical constants of single crystal Bi2Te3 in the NIR to the MIR range, followed by fabrication and characterization of metasurface disk arrays. We show that these high permittivity metasurfaces can yield very large absorption resonances using deep subwavelength structures. Finally, we demonstrate ultra-wide dynamic tuning of PbTe meta-atoms and metasurfaces, utilizing the anomalously large thermo-optic …

The intercalation of layered compounds is a promising route for scalable synthesis of 2D heterostructures with novel emergent optoelectronic properties. Here, we investigate, via first principles calculations, the intercalation of zerovalent metals within the van der Waals gap of bulk MoS 2. Specifically, we focus on a novel Cu-MoS 2 hybrid that accommodates uniform, continuous 2D layers of metallic Cu within the vdW gap of MoS 2. We study the evolution of the Cu-MoS 2 hybrid with increasing Cu content and examine the consequences for intercalation energetics and optoelectronic properties as the intercalated Cu evolves from disordered clusters to contiguous layers. We identify an emergent plasmon resonance (~ 1eV) that is unique to the Cu-MoS 2 hybrid, arising from resonant 2D Cu states within the MoS 2 band gap. Our calculations are shown to be in good agreement with experiments and help explain the …

Delivery of therapeutics to tumors is a major challenge, due to the sequence of formidable biological barriers in the body and tumor, which limit the penetration of various nano-carriers and drugs into the tumor. Exosomes are promising vectors for delivery of anti-tumor therapies, due to their biocompatibility, ability to evade clearance, and innate ability to home to, and interact with, target cells. However, promoting clinical application of exosome-based therapeutics requires elucidation of key issues, including exosome bio-distribution, tumor targeting, and the ability to overcome tumor barriers. Here, we examined these parameters using mesenchymal stem cell (MSCs)-derived exosomes loaded with gold nanoparticles (GNPs), aiming to delineate design principles for therapy loading and delivery. This novel technology provides essential and fundamental knowledge on exosomes for enhanced targeted drug …

Topological insulators (TIs) are a new class of condensed matter system that host topologically protected surface states, leading to dissipationless electron transport. This intrinsic characteristic makes them potential candidate for quantum computing owing to their ability to preserve quantum coherence. Recently, these systems and the concept of topology have been embraced by the photonics community as well. In this work, we study the mid-infrared optical properties of high index (n~5.2) TI bismuth selenide (Bi2Se3) nanobeams (NBs), grown by chemical vapor deposition. Using Finite-difference time-domain (FDTD) simulations and FTIR nanospectroscopy, we find that these NBs support size-tunable Mie-resonant modes across the infrared (~1-16 µm). Furthermore, polarized measurements reveal that the total optical response of these deep subwavelength NBs is composed of TE and TM resonant mode. Finally …

Functional polymers are increasingly recognized for their ability to engineer the electronic properties of 2D materials for device performance enhancement. Although dipole-rich polymer zwitterions have shown significant work function modulation of 2D materials, the contribution of zwitterion structure is not well understood. To this end, a series of zwitterionic sulfobetaine-based random copolymers with varying substituents has been prepared and applied as negative-tone resists on graphene, enabling evaluation of surface potential contrast. The influence of steric footprint on calculated dipole moment and resulting work function measured by ultraviolet photoelectron spectroscopy will be presented. To assess the nature of graphene surface doping by polymer zwitterions, a sample geometry that permits direct access to either the polymer or graphene side is employed using a zwitterionic phosphorylcholine-based …

We present a study of various compositions of the chalcogenide family used for static and active metasurfaces. We start with large area CVD grown amorphous spherical Selenium nanoparticles on various substrates and show that their Mie-resonant response spans the entire mid-infrared (MIR) range. By coupling Se Mie-resonators to ENZ substrates we demonstrate an order of magnitude increase in quality factor. Next, we investigate topological insulators Bi2Se3 and Bi2Te3 metasurfaces. We study the optical constants of single crystal Bi2Te3 in the NIR to the MIR range, followed by fabrication and characterization of metasurface disk arrays. We show that these high permittivity metasurfaces can yield very large absorption resonances using deep subwavelength structures. Finally, we demonstrate ultra-wide dynamic tuning of PbTe meta-atoms and metasurfaces, utilizing the anomalously large thermo-optic …