Conjugation of Amphiphilic Proteins to Hydrophobic Ligands in Organic Solvent.

Protein-ligand conjugations are usually carried out in aqueous media in order to mimic the environment within which the conjugates will be used. In this work, we focus on the conjugation of amphiphilic variants of elastin-like polypeptide (ELP), short elastin (sEL), to poorly water-soluble compounds like OPPVs ( p-phenylenevinylene oligomers), triarylamines, and polypyridine-metal complexes. These conjugations are problematic when carried out in aqueous phase because hydrophobic ligands tend to avoid exposure to water, which in turn causes the ligand to self-aggregate and/or interact noncovalently with hydrophobic regions of the amphiphile. Ultimately, this behavior leads to low conjugation efficiency and contamination with strong noncovalent "conjugates". After exploring the solubility of sEL in various organic solvents, we have established an efficient conjugation methodology for obtaining covalent conjugates virtually free of contaminating noncovalent complexes. When conjugating carboxylated ligands to the amphiphile amines, we demonstrate that even when only one amine (the N-terminus) is present, its derivatization is 98% efficient. When conjugating amine moieties to the amphiphile carboxyls (a problematic configuration), protein multimerization is avoided, 98-100% of the protein is conjugated, and the unreacted ligand is recovered in pure form. Our syntheses occur in "one pot", and our purification procedure is a simple workup utilizing a combination of water and organic solvent extractions. This conjugation methodology might provide a solution to problems arising from solubility mismatch of protein and ligand, and it is likely to be widely applied for modification of recombinant amphiphiles used for drug delivery (PEG-antibodies, polymer-enzymes, food proteins), cell adhesion (collagen, hydrophobins), synthesis of nanostructures (peptides), and engineering of biocompatible optoelectronics (biological polymers), to cite a few.

Electrochromism and Nonvolatile Memory Device Derived from Triphenylamine-Based Polyimides with Pendant Viologen Units.

Three novel solution-processable polyimides containing triphenylamine and pendant viologen moieties are prepared from the newly synthesized diamine and three commercially available dianhydrides. The thermally stable polyimide with strong donor-acceptor charge-transfer possesses write-once read-many-times memory behavior with excellent operation stability. The obtained multicolored electrochromic polymer films reveal ambipolar electrochemical behavior with high optical transmittance contrast of coloration changed from transmissive neutral state to the cyan/magenta/yellow redox states, implying great potential for application in smart window and displays.

Lithium-Ion Dynamic and Storage of Atomically Precise Halogenated Nanographene Assemblies via Bottom-Up Chemical Synthesis.

Graphene has received much scientific attention as an electrode material for lithium-ion batteries because of its extraordinary physical and electrical properties. However, the lack of structural control and restacking issues have hindered its application as carbon-based anode materials for next generation lithium-ion batteries. To improve its performance, several modification approaches such as edge-functionalization and electron-donating/withdrawing substitution have been considered as promising strategies. In addition, group 7A elements have been recognized as critical elements due to their electronegativity and electron-withdrawing character, which are able to further improve the electronic and structural properties of materials. Herein, we elucidated the chemistry of nanographenes with edge-substituted group 7A elements as lithium-ion battery anodes. The halogenated nanographenes were synthesized via bottom-up organic synthesis to ensure the structural control. Our study reveals that the presence of halogens on the edge of nanographenes not only tunes the structural and electronic properties but also impacts the material stability, reactivity, and Li+ storage capability. Further systematic spectroscopic studies indicate that the charge polarization caused by halogen atoms could regulate the Li+ transport, charge transfer energy, and charge storage behavior in nanographenes. Overall, this study provides a new molecular design for nanographene anodes aiming for next-generation lithium-ion batteries.

Redox-Active High-Performance Polyimides as Versatile Electrode Materials for Organic Lithium- and Sodium-Ion Batteries.

Organic electrode materials for rechargeable batteries show great promise for improving the storage capacity, reducing production costs, and minimizing environmental impact toward sustainability. In this study, we report a series of newly synthesized arylamine-based polyimides, TPPA-PIs, with three different bridge functionalizations on the imide rings and isomeric constituents that can work as versatile battery electrodes. As a lithium-ion battery cathode, a maximum energy density of 248 Wh kg-1 with high voltage operation up to 4.0 V can be achieved. As a lithium-ion battery anode, the TPPA-PIs showed a reversible storage capacity of 806 mA h g-1 at 100 mA g-1 current density with good rate capability up to a current density of 2000 mA g-1. Moreover, when applied as sodium-ion battery anodes, TPPA-PIs delivered an optimum specific capacity of up to 218 mA h g-1 after 50 cycles at a 50 mA g-1 current density and revealed a long cycling stability up to 1000 cycles under a high current density of 1000 mA g-1. More importantly, these electrochemical performances of TPPA-PIs are among the best compared with other reported polymer-based electrodes. The mechanistic studies show that both bridge functionalization on the imide units and isomerism impact the electrochemical performance by regulating their intrinsic properties such as charge storage behavior, ion diffusivity, and activation energy. We believe that such a detailed study of the structural design to electrochemical performance of these polymeric electrodes will offer insights into materials development and optimization for next-generation multifunctional energy storage devices in a wide range of applications.

Formation of a CoMn-Layered Double Hydroxide/Graphite Supercapacitor by a Single Electrochemical Step.

Hybrid electric storage systems that combine capacitive and faradaic materials need to be well designed to benefit from the advantages of batteries and supercapacitors. The ultimate capacitive material is graphite (GR), yet high capacitance is usually not achieved due to restacking of its sheets. Therefore, an appealing approach to achieve high power and energy systems is to embed a faradaic 2D material in between the graphite sheets. Here, a simple one-step approach was developed, whereby a faradaic material [layered double hydroxide (LDH)] was electrochemically formed inside electrochemically exfoliated graphite. Specifically, GR was exfoliated under negative potentials by CoII and, in the presence of MnII , formed GR-CoMn-LDH, which exhibited a high areal capacitance and energy density. The high areal capacitance was attributed to the exfoliation of the graphite at very negative potentials to form a 3D foam-like structure driven by hydrogen evolution as well as the deposition of CoMn-LDH due to hydroxide ion generation inside the GR sheets. The ratio between the CoII and MnII in the CoMn-LDH was optimized and analyzed, and the electrochemical performance was studied. Analysis of a cross-section of the GR-CoMn-LDH confirmed the deposition of LDH inside the GR layers. The areal capacitance of the electrode was 186 mF cm-2 at a scan rate of 2 mV s-1 . Finally, an asymmetric supercapacitor was assembled with GR-CoMn-LDH and exfoliated graphite as the positive and negative electrodes, respectively, yielding an energy density of 96.1 µWh cm-3 and a power density of 5 mW cm-3 .

Graphdiyne-Based Nanofilms for Compliant On-Skin Sensing.

Thin-film electronics pliably laminated onto the epidermis for noninvasive, specific, and multifunctional sensing are ideal wearable systems for health monitoring and information technologies. However, it remains a critical challenge to fabricate ultrathin and compliant skin-like sensors with high imperceptibility and sensitivities. Here we report a design of conductive hydrogen-substituted graphdiyne (HsGDY) nanofilms with conjugated porous structure and inherent softness for on-skin sensors that allow minimization of stress and discomfort with wear. Dominated by the subtle deformation-induced changes in the interdomain tunneling conductance, the engineered HsGDY sensors show continuous and accurate results. Real-time noninvasive spatial mapping of dynamic/static strains in both tensile/compressive directions monitors various body motions with high sensitivity (GF ∼22.6, under 2% strain), fast response (∼60 ms), and long-term durability (∼5000 cycles). Moreover, such devices can dynamically distinguish between the temperature difference and frequency of air inhaled and exhaled through the nostril, revealing a quantitative assessment of the movement/health of the human body. The proof-of-concept strategy provides an alternative route for the design of next-generation wearable organic bioelectronics with multiple electronic functionalities.

Dicyanotriphenylamine-Based Polyimides as High-Performance Electrodes for Next Generation Organic Lithium-Ion Batteries.

Aromatic polyimide (PI) derivatives have recently been investigated as redox-active electrode materials for Li-ion batteries because of their high thermal stability and thermo-oxidative stability complemented by excellent solvent resistance, good electrical and mechanical properties, and chemical resistance. In this work, we report two PI derivatives from a newly synthesized 4,4'-diamino-3″,4″-dicyanotriphenylamine (DiCN-TPA) monomer and two dianhydrides, pyromellitic dianhydride (PMDA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA); designated as TPA-PMPI and TPA-NTCPI, respectively, as electrode materials for Li-ion batteries. Characterizations of the PIs reveal excellent thermal stability and bipolar property. The incorporation of DiCN-TPA into the polymer structure resulted to a disordered chain arrangement, thus giving high glass transition temperatures (Tg). Electrochemical performance tests reveal that TPA-NTCPI cathode delivered a reversible specific capacity of 150 mAh g-1 at 0.1 A g-1 and exhibited a stability up to 1000 cycles. On the other hand, TPA-PMPI anode delivered a high specific capacity of up to 1600 mAh g-1 at 0.1 A g-1 after 100 cycles. The electrochemical performance of TPA-NTCPI cathode and TPA-PMPI anode are both among the best compared with other reported aromatic PI-based electrodes. The long cycle lifetime and excellent battery performance further suggest that TPA-NTCPI and TPA-PMPI are promising organic electrode materials for next generation Li-ion batteries.

Graphene Oxides Used as a New "Dual Role" Binder for Stabilizing Silicon Nanoparticles in Lithium-Ion Battery.

For the first time, we report that graphene oxide (GO) can be used as a new "dual-role" binder for Si nanoparticles (SiNPs)-based lithium-ion batteries (LIBs). GO not only provides a graphene-like porous 3D framework for accommodating the volume changes of SiNPs during charging/discharging cycles, but also acts as a polymer-like binder that forms strong chemical bonds with SiNPs through its Si-OH functional groups to trap and stabilize SiNPs inside the electrode. Leveraging this unique dual-role of GO binder, we fabricated GO/SiNPs electrodes with remarkably improved performances as compared to using the conventional polyvinylidene fluoride (PVDF) binder. Specifically, the GO/SiNPs electrode showed a specific capacity of 2400 mA h g-1 at the 50th cycle and 2000 mA h g-1 at the 100th cycle, whereas the SiNPs/PVDF electrode only showed 456 mAh g-1 at the 50th cycle and 100 mAh g-1 at 100th cycle. Moreover, the GO/SiNPs film maintained its structural integrity and formed a stable solid-electrolyte interphase (SEI) film after 100 cycles. These results, combined with the well-established facile synthesis of GO, indicate that GO can be an excellent binder for developing high performance Si-based LIBs.

Development of Conjugated Polymers for Memory Device Applications.

This review summarizes the most widely used mechanisms in memory devices based on conjugated polymers, such as charge transfer, space charge traps, and filament conduction. In addition, recent studies of conjugated polymers for memory device applications are also reviewed, discussed, and differentiated based on the mechanisms and structural design. Moreover, the electrical conditions of conjugated polymers can be further fine-tuned by careful design and synthesis based on the switching mechanisms. The review also emphasizes and demonstrates the structure-memory properties relationship of donor-acceptor conjugated polymers for advanced memory device applications.

Large Grained Perovskite Solar Cells Derived from Single-Crystal Perovskite Powders with Enhanced Ambient Stability.

In this study, we demonstrate the large grained perovskite solar cells prepared from precursor solution comprising single-crystal perovskite powders for the first time. The resultant large grained perovskite thin film possesses a negligible physical (structural) gap between each large grain and is highly crystalline as evidenced by its fan-shaped birefringence observed under polarized light, which is very different from the thin film prepared from the typical precursor route (MAI + PbI2).

Structurally Defined 3D Nanographene Assemblies via Bottom-Up Chemical Synthesis for Highly Efficient Lithium Storage.

Functionalized 3D nanographenes with controlled electronic properties have been synthesized through a multistep organic synthesis method and are further used as promising anode materials for lithium-ion batteries, exhibiting a much increased capacity (up to 950 mAh g-1 ), three times higher than that of the graphite anode (372 mAh g-1 ).

Tyrosine-derived stimuli responsive, fluorescent amino acids.

A series of fluorescent unnatural amino acids (UAAs) bearing stilbene and meta-phenylenevinylene (m-PPV) backbone have been synthesized and their optical properties were studied. These novel UAAs were derived from protected diiodo-l-tyrosine using palladium-catalyzed Heck couplings with a series of styrene analogs. Unlike the other fluorescent UAAs, whose emissions are restricted to a narrow range of wavelengths, these new amino acids display the emission peaks at broad range wavelengths (from 400-800 nm); including NIR with QY of 4% in HEPES buffer. The incorporation of both pyridine and phenol functional groups leads to distinct red, green, and blue (RGB) emission, in its basic, acidic and neutral states, respectively. More importantly, these amino acids showed reversible pH and redox response showing their promise as stimuli responsive fluorescent probes. To further demonstrate the utility of these UAAs in peptide synthesis, one of the amino acids was incorporated into a cell penetrating peptide (CPP) sequence through standard solid phase peptide synthesis. Resultant CPP was treated with two different cell lines and the internalization was monitored by confocal fluorescence microscopy.

Novel triarylamine-based polybenzoxazines with a donor-acceptor system for polymeric memory devices.

Novel polybenzoxazines consisting of electron-donating triphenylamine derivatives and electron-withdrawing 4,4'-diphenyl sulfone moieties were successfully prepared by the thermally induced ring-opening reaction of the corresponding PB precursors and utilized for memory devices.

Colorless triphenylamine-based aliphatic thermoset epoxy for multicolored and near-infrared electrochromic applications.

In this study, two novel colorless thermoset epoxy resins with anodically electrochromism were prepared from the thermal curing of two triphenylamine-based diamine monomers, 4,4'-diamino-4″-methoxytriphenylamine (1) and N,N'-bis(4-aminophenyl)-N,N'-di(4-methoxylphenyl)-1,4-phenylenediamine (2) with aliphatic epoxy triglycidyl isocyanurate, respectively. The resulting thermoset epoxy resins showed excellent softening temperature (Ts, 270 and 280 °C) due to the rigid structure and highly crosslinking density. In addition, novel colorless epoxy resin films revealed good reversible electrochemical oxidation and interesting multi-electrochromic behavior with high contrast ratio both in visible and near-infrared regions. The aliphatic thermoset epoxy resins also exhibited high transparency in visible region as colorless and great potential for practical electrochromic applications.

Side-chain and linkage-mediated effects of anthraquinone moieties on ambipolar poly(triphenylamine)-based volatile polymeric memory devices.

Two ambipolar and thermally stable poly(triphenylamine)s with pendent anthraquinone acceptors were readily synthesized and prepared for the investigation of side-chain and linkage-mediated effects on the memory behaviour.

Flexible electrofluorochromic devices with the highest contrast ratio based on aggregation-enhanced emission (AEE)-active cyanotriphenylamine-based polymers.

Flexible electrofluorochromic devices were prepared from two electrochromic and AEE-active (AEE: aggregation-enhanced emission) cyanoarylamine-containing high-performance polymers, exhibiting the highest contrast ratio (If/If0) of 151.9 at a low working potential.

Novel high-efficiency PL polyimide nanofiber containing aggregation-induced emission (AIE)-active cyanotriphenylamine luminogen.

Two aggregation-induced emission (AIE)-active high-performance polymers and their electrospun (ES) nanofibers were synthesized and prepared. Strong luminescence is induced when they are aggregated in poor solvents or fabricated into solid films and this is further enhanced when they are prepared as ES nanofibers, demonstrating their AIE feature and great potential for optoelectronic applications.

A facile approach to multicolored electrochromic triarylamine-based thermoset epoxy materials with tunable intervalence charge transfer behavior.

By a facile curing reaction, novel electrochromic triarylamine-based thermosetting epoxy materials could be readily prepared for the first time. The resulting multielectrochromic epoxy materials exhibited good electrochemical stability and large optical changes in transmittance between their bleached and colored states with tunable intervalence charge transfer behavior.