A metal-organic framework-based fluorescence resonance energy transfer nanoprobe for highly selective detection of Staphylococcus Aureus.

Survival and infection of pathogenic bacteria, such as Staphylococcus aureus (S. aureus), pose a serious threat to human health. Efficient methods for recognizing and quantifying low levels of bacteria are imperiously needed. Herein, we introduce a metal-organic framework (MOF)-based fluorescence resonance energy transfer (FRET) nanoprobe for ratiometric detection of S. aureus. The nanoprobe utilizes blue-emitting 7-hydroxycoumarin-4-acetic acid (HCAA) encapsulated inside zirconium (Zr)-based MOFs as the energy donor and green-emitting fluorescein isothiocyanate (FITC) as the energy acceptor. Especially, vancomycin (VAN) is employed as the recognition moiety to bind to the cell wall of S. aureus, leading to the disassembly of VAN-PEG-FITC from MOF HCAA@UiO-66. As the distance between the donor and acceptor increases, the donor signal correspondingly increases as the FRET signal decreases. By calculating the fluorescence intensity ratio, S. aureus can be quantified with a dynamic range of 1.05 × 103-1.05 × 107 CFU mL-1 and a detection limit of 12 CFU mL-1. Due to the unique high affinity of VAN to S. aureus, the nanoprobe shows high selectivity and sensitivity to S. aureus, even in real samples like lake water, orange juice, and saliva. The FRET-based ratiometric fluorescence bacterial detection method demonstrated in this work has a prospect in portable application and may reduce the potential threat of pathogens to human health.

Stretchable and self-healable spoof plasmonic meta-waveguide for wearable wireless communication system.

Microwave transmission lines in wearable systems are easily damaged after frequent mechanical deformation, posing a severe threat to wireless communication. Here, we report a new strategy to achieve stretchable microwave transmission lines with superior reliability and durability by integrating a self-healable elastomer with serpentine-geometry plasmonic meta-waveguide to support the spoof surface plasmon polariton (SSPP). After mechanical damage, the self-healable elastomer can autonomously repair itself to maintain the electromagnetic performance and mechanical strength. Meanwhile, the specially designed SSPP structure exhibits excellent stability and damage resistance. Even if the self-healing process has not been completed or the eventual repair effect is not ideal, the spoof plasmonic meta-waveguide can still maintain reliable performance. Self-healing material enhances strength and durability, while the SSPP improves stability and gives more tolerance to the self-healing process. Our design coordinates the structural design with material synthesis to maximize the advantages of the SSPP and self-healing material, significantly improving the reliability and durability of stretchable microwave transmission lines. We also perform communication quality experiments to demonstrate the potential of the proposed meta-waveguide as interconnects in future body area network systems.

A high mobility air-stable n-type organic small molecule semiconductor with high UV-visible-to-NIR photoresponse.

An organic semiconductor with high carrier mobility and efficient light absorption over a wide spectral range is of the most important yet challenging material for constructing a broadband responsive organic photodetector. However, the development of such organic semiconductors, especially for air-stable n-type organic small molecule semiconductors, is still at an early stage. Here we report the fabrication of high-performance n-type semiconducting crystalline nanosheets and the development of air-stable field-effect transistors, phototransistors, with high response over a broad spectrum. The n-type small molecule semiconductor is assembled into a crystalline nanosheet based on the solvent-phase interfacial self-assembly method. N-type field-effect transistors with high electron mobility are fabricated and their electrical performances exhibit excellent air stability. Impressively, the demonstrated phototransistors exhibit an ultrahigh responsivity over a wide spectral range from 365 to 940 nm, with a maximum photoresponsivity of 9.2 × 105 A W-1 and specific detectivity of 5.26 × 1013 Jones, which is the best performance among the reported n-type organic small molecule-based phototransistors.

Air/water interfacial assembled rubbery semiconducting nanofilm for fully rubbery integrated electronics.

A rubber-like stretchable semiconductor with high carrier mobility is the most important yet challenging material for constructing rubbery electronics and circuits with mechanical softness and stretchability at both microscopic (material) and macroscopic (structural) levels for many emerging applications. However, the development of such a rubbery semiconductor is still nascent. Here, we report the scalable manufacturing of high-performance stretchable semiconducting nanofilms and the development of fully rubbery transistors, integrated electronics, and functional devices. The rubbery semiconductor is assembled into a freestanding binary-phased composite nanofilm based on the air/water interfacial assembly method. Fully rubbery transistors and integrated electronics, including logic gates and an active matrix, were developed, and their electrical performances were retained even when stretched by 50%. An elastic smart skin for multiplexed spatiotemporal mapping of physical pressing and a medical robotic hand equipped with rubbery multifunctional electronic skin was developed to show the applications of fully rubbery-integrated functional devices.

Ultra-conformal drawn-on-skin electronics for multifunctional motion artifact-free sensing and point-of-care treatment.

An accurate extraction of physiological and physical signals from human skin is crucial for health monitoring, disease prevention, and treatment. Recent advances in wearable bioelectronics directly embedded to the epidermal surface are a promising solution for future epidermal sensing. However, the existing wearable bioelectronics are susceptible to motion artifacts as they lack proper adhesion and conformal interfacing with the skin during motion. Here, we present ultra-conformal, customizable, and deformable drawn-on-skin electronics, which is robust to motion due to strong adhesion and ultra-conformality of the electronic inks drawn directly on skin. Electronic inks, including conductors, semiconductors, and dielectrics, are drawn on-demand in a freeform manner to develop devices, such as transistors, strain sensors, temperature sensors, heaters, skin hydration sensors, and electrophysiological sensors. Electrophysiological signal monitoring during motion shows drawn-on-skin electronics' immunity to motion artifacts. Additionally, electrical stimulation based on drawn-on-skin electronics demonstrates accelerated healing of skin wounds.

A highly conductive, transparent molecular charge-transfer salt with reversible lithiation.

Here, we describe the high conductivity in a molecular charge-transfer hydrocarbon both as a bulk solid and films. In particular, the high electrical conductivity (∼30 S cm-1) and transparency (∼80%) of the TTF-TCNQ thin film allowed us to develop its application in all-organic freestanding photodetectors. More importantly, the fabricated TTF-TCNQ thin film can be used as a lithium-ion battery electrode with a specific capacity of ∼250 mA h g-1.

Exciton-dipole coupling in two-dimensional rubrene assembly sensors.

The selective detection of molecules with less energy consumption depends critically on novel sensing concepts and the emergence of new sensor materials. Excitons and dipole moments are two strongly correlated states that have shown coupled electronic interactions on the nanoscale, and they are highly sensitive to changes in their surroundings. Here, we present exciton-dipole coupling in the two-dimensional (2D) assembly of molecular rubrene excitonic crystals to selectively detect molecules. The presence of molecules with a dipole moment transforms excitons into charge transfer, resulting in a pronounced conductivity change of freestanding rubrene nanosheets. The exciton-dipole coupling exhibits highly efficient molecular selectivity, as it offers an unambiguous electronic fingerprint for the detection of molecules - in contrast to common sensing schemes relying on the quantification of intensity changes and optical peak shifts.

Strongly Correlated Aromatic Molecular Conductor.

Strongly correlated electronic molecules open the way for strong coupling between charge, spin, and lattice degrees of freedom to enable interdisciplinary fields, such as molecular electronic switches and plasmonics, spintronics, information storage, and superconducting circuits. However, despite exciting computational predictions and promising advantages to prepare flexible geometries, the electron correlation effect in molecules has been elusive. Here, the electron correlation effects of molecular plasmonic films are reported to uncover their coupling of charge, spin, lattice, and orbital for the switchable metal-to-insulator transition under external stimuli, at which the simultaneous transition occurs from the paramagnetic, electrical, and thermal conducting state to the diamagnetic, electrical, and thermal insulating state. In addition, density functional theory calculation and spectroscopic studies are combined to provide the mechanistic understanding of electronic transitions and molecular plasmon resonance observed in molecular conducting films. The self-assembled molecular correlated conductor paves the way for the next generation integrated micro/nanosystems.

Ubiquitous energy conversion of two-dimensional molecular crystals.

Two-dimensional (2D) atomic crystals have triggered significant excitement due to their rich physics as well as potential industrial applications. The possibility of a molecular counterpart with scalable processability and superior performance is intriguing from both fundamental and applied perspectives. Here, we present the freestanding 2D molecular charge-transfer bis(ethylenedithio)tetrathiafulvalene-C60 crystals prepared by a modified Langmuir-Blodgett method, with precisely controlled few-layer thickness and centimeter-scale lateral dimension. The interconversion of intrinsic excited process, the long-range ordering and anisotropic stacking arrangement of the molecular layered crystals generate external stimuli responsive behaviors and anisotropic spin-charge conversion with magnetic energy conversion ability, as well as a superior UV photosensitivity. Moreover, the 2D freestanding crystals demonstrate superior magneto-electrical properties. These results suggest that a new class of 2D atomically thin molecular crystals with novel electronic, optical and magnetic properties have great potential for spintronic, energy and sensor applications.

Alkali-Metal-Intercalated Percolation Network Regulates Self-Assembled Electronic Aromatic Molecules.

In the continuously growing field of correlated electronic molecular crystals, there is significant interest in addressing alkali-metal-intercalated aromatic hydrocarbons, in which the possibility of high-temperature superconductivity emerges. However, searching for superconducting aromatic molecular crystals remains elusive due to their small shielding fraction volume. To exploit this potential, a design principle for percolation networks of technologically important film geometry is indispensable. Here the effect of potassium-intercalation is shown on the percolation network in self-assembled aromatic molecular crystals. It is demonstrated that one-dimensional (1D) dipole pairs, induced by dipole interaction, regulate the conductivity, as well as the electronic and optical transitions, in alkali-metal-intercalated molecular electronic crystals. A solid-solution growth methodology of aromatic molecular films with a broad range of stability is developed to uncover electronic and optical transitions of technological importance. The light-induced electron interactions enhance the charge-carrier itinerancy, leading to a switchable metal-to-insulator transition. This discovery opens a route for the development of aromatic molecular electronic solids and long-term modulation of electronic efficacy in nanotechnologically important thin films.

Magnetoelectric Radical Hydrocarbons.

The molecular radicals, systems with unpaired electrons of open-shell electronic structures, set the stage for a multidisciplinary science frontier relevant to the cooperative magnetic exchange interaction and magnetoelectric effect. Here ferroelectricity together with magnetic spin exchange coupling in molecular radical hydrocarbon solids is reported, representing a new class of magnetoelectrics. Electronic correlation through radical-radical interactions plays a decisive role in the coupling between magnetic and charge orders. A substantial photoconductance and visible-light photovoltaic effect are found in radical hydrocarbons. The ability to simultaneously control and retrieve the changes in magnetic and electrical responses opens up a new breadth of applications, such as radical magnetoelectrics, magnets, and optoelectronics.

Three-dimensional directed assembly of organic charge-transfer heterostructure.

Multicomponent crystalline heterostructures are a powerful approach to integrate different functional materials into the ordered structures. Here we describe three-dimensional spherical assembly of binary organic solids that consist of electron donor and acceptor molecules. A mechanistic study of heterostructure formation reveals that the dewetting and drying-mediated assembly processes are responsible for the spherical crystallite formation. The assembled spherical heterostructures are highly tunable, crystalline and chemically stable, exhibiting phase separation controlled optoelectronic behavior. This simple, generalizable three-dimensional assembly can be modified for the formation of ordered functional organic multicomponent heterostructures for emerging applications.

Kirigami-Inspired Conducting Polymer Thermoelectrics from Electrostatic Recognition Driven Assembly.

Two-dimensional (2D) conducting polymers are expected to offer emergent topological, structural, and physical properties, which has become the "holy grail" for the development of plastic electronics. Here, we report the assembly of a free-floating metallic polymer layer, consisting of poly(3,4-ethylenedioxythiophene) complexed with poly(styrenesulfonate) anions, directed by electrostatic recognition, amphiphilicity, and aromatic interactions. The obtained large-area crystalline nanosheets exhibit excellent environmental stability and mechanical robustness, meanwhile showing an electrical conductivity of 1216 S·cm-1, the highest among the nanometer-thick conducting polymers. The kirigami-inspired freestanding polymer thermoelectrics, repeatedly stretching up to 200% strain, is demonstrated with high Seebeck coefficient with an optimized power factor of 95 µW m-1 K-2. The large-scale assembly and aqueous compatibility of 2D conducting polymers provide an exciting platform for integrating thermoelectricity into free-floating polymer nanostructures.

Kirigami-Inspired Nanoconfined Polymer Conducting Nanosheets with 2000% Stretchability.

Stretchable conductors are essential components of wearable electronics. However, such materials typically sacrifice their electronic conductivity to achieve mechanical stretchability and elasticity. Here, the nanoconfinement and air/water interfacial assembly is explored to grow freestanding mechanical endurance conducting polymer nanosheets that can be stretched up to 2000% with simultaneously high electrical conductivity, inspired by kirigami. Such stretchable conductors show remarkable electronic and mechanical reversibility and reproducibility under more than 1000 cycle durability tests with 2000% deformability, which can be accurately predicted using finite element modeling. The conductivity of nanoconfined freestanding conductor nanosheets increases by three orders of magnitude from 2.2 × 10-3 to 4.002 S cm-1 is shown, due to the charge-transfer complex formation between polymer chain and halogen, while the electrical conductance of the stretchable kirigami nanosheets can be maintained over the entire strain regime. The nanoconfined polymer nanosheets can also act as a sensor capable of sensing the pressure with high durability and real-time monitoring.

Flexible n-Type High-Performance Thermoelectric Thin Films of Poly(nickel-ethylenetetrathiolate) Prepared by an Electrochemical Method.

Flexible thin films of poly(nickel-ethylenetetrathiolate) prepared by an electrochemical method display promising n-type thermoelectric properties with the highest ZT value up to 0.3 at room temperature. Coexistence of high electrical conductivity and high Seebeck coefficient in this coordination polymer is attributed to its degenerate narrow-bandgap semiconductor behavior.

Donor-acceptor co-assembled supramolecular nanofibers with high and well-balanced ambipolar charge transport properties under ambient conditions.

Single-bundle nanofiber based OFETs were fabricated from co-assembled supramolecular nanofibers which comprise TCAT and PDI-13, using a simple gelation method. The co-assembled supramolecular nanoarchitecture was fully characterized by means of optical microscopy, TEM, SEM, 2D-GIWAXS and so on. The devices exhibited typical ambipolar charge transport characteristics with very well-balanced hole and electron mobilities as well as high photoresponsivity under ambient conditions.

Single-bundle nanofiber based OFETs fabricated from a cyclic conjugated organogelator with high field-effect mobility and high photoresponsivity.

Single-bundle nanofiber based OFETs were fabricated from a cyclic conjugated organogelator, using a simple gelation method. The devices exhibited typical p-type semiconductor properties with dominant hole transport both in the dark and upon illumination under ambient conditions.

Thiophene-Diketopyrrolopyrrole-Based Quinoidal Small Molecules as Solution-Processable and Air-Stable Organic Semiconductors: Tuning of the Length and Branching Position of the Alkyl Side Chain toward a High-Performance n-Channel Organic Field-Effect Transistor.

A series of thiophene-diketopyrrolopyrrole-based quinoidal small molecules (TDPPQ-2-TDPPQ-5) bearing branched alkyl chains with different side-chain lengths and varied branching positions are synthesized. Field-effect transistor (FET) measurement combined with thin-film characterization is utilized to systematically probe the influence of the side-chain length and branching position on the film microstructure, molecular packing, and, hence, charge-transport property. All of these TDPPQ derivatives show air-stable n-channel transporting behavior in spin-coated FET devices, which exhibit no significant decrease in mobility even after being stored in air for 2 months. Most notably, TDPPQ-3 exhibits an outstanding n-channel semiconducting property with electron mobilities up to 0.72 cm(2) V(-1) s(-1), which is an unprecedented value for spin-coated DPP-based n-type semiconducting small molecules. A balance of high crystallinity, satisfactory thickness uniformity and continuity, and strong intermolecular interaction accounts for the superior charge-transport characteristics of TDPPQ-3 films. Our study demonstrates that tuning the length and branching position of alkyl side chains of semiconducting molecules is a powerful strategy for achieving high FET performance.

A fluorometric paper-based sensor array for the discrimination of heavy-metal ions.

A fluorometric paper-based sensor array has been developed for the sensitive and convenient determination of seven heavy-metal ions at their wastewater discharge standard concentrations. Combining with nine cross-reactive BODIPY fluorescent indicators and array technologies-based pattern-recognition, we have obtained the discrimination capability of seven different heavy-metal ions at their wastewater discharge standard concentrations. After the immobilization of indicators and the enrichment of analytes, identification of the heavy-metal ions was readily acquired using a standard chemometric approach. Clear differentiation among heavy-metal ions as a function of concentration was also achieved, even down to 10(-7)M. A semi-quantitative estimation of the heavy-metal ion concentration was obtained by comparing color changes with a set of known concentrations. The sensor array was tentatively investigated in spiked tap water and sea water, and showed possible feasibility for real sample testing.

BODIPY-based fluorometric sensor array for the highly sensitive identification of heavy-metal ions.

A BODIPY(4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)-based fluorometric sensor array has been developed for the highly sensitive detection of eight heavy-metal ions at micromolar concentration. The di-2-picolyamine (DPA) derivatives combine high affinities for a variety of heavy-metal ions with the capacity to perturb the fluorescence properties of BODIPY, making them perfectly suitable for the design of fluorometric sensor arrays for heavy-metal ions. 12 cross-reactive BODIPY fluorescent indicators provide facile identification of the heavy-metal ions using a standard chemometric approach (hierarchical clustering analysis); no misclassifications were found over 45 trials. Clear differentiation among heavy-metal ions as a function of concentration was also achieved, even down to 10(-7)M. A semi-quantitative interpolation of the heavy-metal concentration is obtained by comparing the total Euclidean distance of the measurement with a set of known concentrations in the library.