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Powering implanted medical devices (IMDs) is a long-term challenge since their use in biological environments requires a long-term and stable supply of power and a biocompatible and biodegradable battery system. Here, silk fibroin-based ion-exchange membranes are developed using bionics principles for reverse electrodialysis devices (REDs). Silk fibroin nanofibril (SNF) membranes are negatively and positively modified, resulting in strong cation and anion selectivity that regulates ion diffusion to generate electric power. These oppositely charged SNF membranes are assembled with Ag/AgCl electrodes into a multicompartment RED. By filling them with 10 and 0.001 mM NaCl solutions, a maximum output power density of 0.59 mW/m

In this work, we demonstrate the principle of mesoscopic construction of silk fibroin (SF) hybrid materials, which endows the materials with new performance. In implementing this strategy, mediating molecules, wool keratin (WK) molecules, were adopted to in-line synthesize Au nanoparticles (WK@AuNPs), which further create the stable linkage of AuNPs with SF nanofibril networks via templated β-crystallization. Fourier transform infrared spectroscopy, X-ray diffraction, and atomic force microscopy demonstrate that the mesoscopic hybrid network structure of the hybrid materials is different from neat SF materials, which gives rise to various new performances, that is, long-stable fluorescence emission. As the fluorescence emission can be characteristically annealed by Cu ions, therefore be adopted as the highly selective ion probes. Moreover, as WK@AuNPs are homogeneously connected to SF nanofibril networks, the carbonization of the materials leads to secondary hybrid materials of carbon-Au, where nano-sized Au particles are well distributed in carbonized mesoscopic conductive carbon networks. Such hybrid materials of carbon-Au can be further fabricated into electrochemical (i.e., dopamine) sensors, which are demonstrated to have excellent sensing performance.

Transmission of energy and signals through human skin is critically important for implantable devices. Because near-infrared (NIR) light can easily penetrate through human skin/tissue, in this study we report on silk fibroin (SF) up-conversion photonic amplifiers (SFUCPAs) integrated into optoelectronic devices, which provide a practical approach for subcutaneous charging and communication via NIR lasers. SFUCPAs achieve a 4 times higher fluorescence than the control, which gives rise to a 47.3 time increase in subcutaneous NIR energy conversion efficiency of a single fibrous dye-sensitized solar cell compared with the control. Moreover, the hybrid printed electrodes exhibited reversible switching to NIR exposure with a response time of ∼1.06/1.63 s for a 3 s ON/OFF switch. Owing to the flexible, biocompatible, and cost-efficient design NIR-driven optoelectronic performance, the SFUCPAs are promising for use in applications of subcutaneous medical electronics for charging, storing information, and controlling implanted devices.

NiCoAl layered double hydroxide nanosheets (NiCoAl-LDHNs) were prepared by a one-step solvothermal method. The shape and size of the obtained nanosheets are optimized by adjusting the solvothermal time and the molar concentration ratio of Ni2+/Co2+ to obtain the electrode material with the best performance. When the solvothermal time is 9 h and the molar concentration ratio of Ni2+/Co2+ is 1:1, NiCoAl-LDHNs has the best morphology and electrochemical performance. When assembled into a supercapacitor, NiCoAl-LDHN-9 has a high specific capacitance of 1228.5 F g−1 at 1 A g−1. As the current density is increased to 20 A g−1, the specific capacitance is 1001.8 F g−1, which still has a high capacitance retention of 81.6%. When NiCoAl-LDHN-9 was assembled into an asymmetric supercapacitor, NiCoAl-LDHN-9//AC has a specific capacitance of 102.1 F g−1 at 0.5 A g−1. The asymmetric supercapacitor devices also show excellent electrochemical performance in terms of energy density (35.9 Wh kg−1 at 225.8 W kg−1), power density (4.8 kW kg−1 at 22.2 Wh kg−1) and cycle life (capacitance retention rate after 10,000 cycles is 87.1%). Those results indicate that NiCoAl-LDHN have the potential to be promising electrode materials for high performance supercapacitors.

Transient devices have attracted extensive interest because they allow changes in physical form and device function under the control of external stimuli or related commands and have very broad application prospects for information security, biomedical care and the environment. Transient bioelectrical devices were fabricated inspired by a silkworm moth breaking out of its cocoon, which has shown many advantages, including the use of mild stimulation, biocompatible materials, a simple process, and a universal strategy. For the fabrication of the transient devices, heat-sensitive microspheres with a 9.3 mol L−1 LiBr solution in wax shells were prepared by microfluidic technology, which were then assembled into silk fibroin (SF) electronic materials/devices, such as SF conductive film, an LED circuit on SF film, and a Ag/SF film/Pt/SF film memristor. The contribution from the LiBr/wax microspheres to the transient time of the SF films upon exposure to heat was quantitatively investigated. This approach was applied to transiently dissolve a flexible Ag-nanowire resistance circuit line on a SF substrate. Moreover, memristors constructed with a functional layer of SF were destroyed by melting the LiBr/wax microspheres. This technique paves the way for realizing transient bioelectrical devices inspired by biological behavior, which have been well optimized by nature via evolution.

A novel flower-like polyaniline/graphene hybrid (PANI-ATRGO) is prepared by a one-pot synthesis and used as electrode materials for supercapacitors. The structure, formation mechanism and electrochemical properties of such unique architecture are systematically investigated by combining Fourier transform infrared spectroscopy, Ultraviolet–visible absorption spectroscopy, Raman spectroscope, X-ray diffraction and electrochemical techniques. The results suggest that “V-type” amino groups of ATRGO and supermolecular assembly between PANI chains play the key role in the formation of flower-like nanostructures. Compare to pristine PANI (487 F g −1 at 1 A g −1 ), PANI-ATRGO electrode materials exhibit a remarkable improvement of the specific capacitance (1510 F g −1 at 1 A g −1 ) for supercapacitor in addition to excellent rate capacity and long-term cycling stability. Moreover, it is found that flower-like PANI-ATRGO hybrids exhibit better electrochemical properties than the corresponding nanorod-array hybrids in our previous study. This reveals the significance of controlling the hierarchical structure of hybrid materials in the development of high-performance supercapacitor.

Turning insulating silk fibroin materials into conductive ones turns out to be the essential step toward achieving active silk flexible electronics. This work aims to acquire electrically conductive biocompatible fibers of regenerated Bombyx mori silk fibroin (SF) materials based on carbon nanotubes (CNTs) templated nucleation reconstruction of silk fibroin networks. The electronical conductivity of the reconstructed mesoscopic functional fibers can be tuned by the density of the incorporated CNTs. It follows that the hybrid fibers experience an abrupt increase in conductivity when exceeding the percolation threshold of CNTs >35 wt%, which leads to the highest conductivity of 638.9 S m-1 among organic-carbon-based hybrid fibers, and 8 times higher than the best available materials of the similar types. In addition, the silk-CNT mesoscopic hybrid materials achieve some new functionalities, i.e., humidity-responsive conductivity, which is attributed to the coupling of the humidity inducing cyclic contraction of SFs and the conductivity of CNTs. The silk-CNT materials, as a type of biocompatible electronic functional fibrous material for pressure and electric response humidity sensing, are further fabricated into a smart facial mask to implement respiration condition monitoring for remote diagnosis and medication.

A series of functional polyacetylenes bearing the fluorene moiety with different conjugated lengths and terminal substituents, poly[2-ethynyl-7-(4-nitrostyryl)-9,9-dioctyl-9H-fluorene] (P1), poly[2-ethynyl-7-(4-(4-nitrostyryl)styryl)-9,9-dioctyl-9H-fluorene] (P2), poly[2-ethynyl-7-(4-(4-methoxystyryl)styryl)-9,9-dioctyl-9H-fluorene] (P3), poly[2-ethynyl-7-(4-(4-methylstyryl)styryl)-9,9-dioctyl-9H-fluorene] (P4), and poly[2-ethynyl-7-(4-(4-methylstyryl)styryl)-9,9-didodecyl-9H-fluorene] (P5), were designed and prepared using [Rh(nbd)Cl]2 as the catalyst. Their structures and properties were characterized and evaluated by FTIR, NMR, UV, FL, GPC and TGA analyses. The optical limiting properties were investigated using 450 fs laser pulses at 780 nm. These results show that the incorporation of styryl/stilbene functionalized polyfluorenylacetylenes has endowed resultant polyacetylenes with novel near-infrared laser protection properties and enhanced thermal stability. The optical limiting mechanism for laser protection was studied. It was found that the optical limiting properties mainly originated from two-photon absorption (TPA) of molecules in the resulting polyacetylenes. Additionally, it was also found that the functionalized polyacetylene with a longer fluorene-based conjugated chromophore and a stronger terminal electron acceptor group exhibits better optical limiting properties because of the larger π-electron delocalization and dipolar effect.

Silk fibers spun by silkworms or spiders at ambient temperature display unique mechanical strength, excellent biocompatibility and optical transparency, which offer unconventional interfaces to soft and curved biological systems. In comparison with conventional materials, the performance of soft matter, i.e., animal silks, is mainly determined by the structure at the mesoscale. To further extend the applications, functionalization of silk materials becomes is required, and mesoscopic material assembly (MMA) was developed for this task. This feature article provides an overview on the principles and strategies concerning MMA, and some typical examples of functionalizing silk fibroin materials. The main strategies of MMA include in vivo and in vitro assemblies, and can be implemented by the three different paths: (1) molecular recognition, (2) surface functionalization of nanomaterials, or (3) foreign molecule mediation. The cases include the functionalization of silk fibroin materials by one/two-photon fluorescent molecules, quantum dots (QDs) and gold clusters, etc. The applications of these functionalized materials in bio waveguide, white-light-emitting devices, bioimaging, were also highlighted. MMA provides a practical tool for the production of the functionalized biocompatible materials, which can be further applied to fabricate high-performance bio integrated devices used in consumer electronics, and biomedical diagnosis, as well as human-machine interfaces.

To fabricate biocompatible composite films with tunable performance, both silk fibroin (SF, β-crystallite rich) and keratin (α-helix rich) materials are engineered at the mesoscale based on the molecular synergy. While SF materials display a hierarchical structure initiated from the β-crystallite molecular networks, keratin materials reveal the networks crossly linked by disulfide bonding. It is surprising to see that the β-crystallites of SF materials induce the conversion of the free unfolded molecular chains of keratin to β-folding (β-crystallites) in the SF/keratin composites. Furthermore, the α-helices from the keratin components in the SF/keratin composites can transit to β-sheets under stress, which gives rise to the strain-hardening, and a better flexibility and elasticity. It follows that the tensile and biodegradable performance of the SF/keratin composites can be programmed by adjusting the ratio of SF versus keratin in the composites. Raising the SF ratio in the composite films increases the density of β-crystallites in the networks, giving rise to the enhanced toughness and reduced biodegradation rate, but poor deformation recovery. On the other hand, increasing the ratio of keratin in the composite films increases the extensibility, strain-hardening effect. These make them excel bio-optical materials with controllable properties.

Here a biomimetic approach is presented to fabricate nanodragon fruits featured by a multitude of tiny quantum dot ZnO seeds embedded in mesosilica (SiO2) flesh then enclosed in amorphous calcium phosphate (ACP) shell. The nanodragon fruits give rise to a new class of hybrid ZnO/SiO2@ACP nanocomplex with multimoidal capability: cellular delivering, intracellular targeting, and subcellular imaging. With this particular design, the unusual fluorescent stability of ZnO quantum dots (QDs) in aqueous solution, the specific color selection of the functional ZnO QD seeds, and the stability of transient ACP over a long period of time are made possible. In addition, the nanodragon fruits, capable of targeting mitochondria, have elevated biocompatibility, thus can be of enormous potential applications in treating mitochondrial diseases including inflammation, neurodegeneration, obesity, diabetes, cardiovascular diseases, and cancer. As numerous human disorders are often associated with cellular dysfunctions, this biocompatible carrying platform, capable of delivering, targeting, and imaging subcellular organelles, is therefore highly desirable for efficacious therapeutic and diagnostic treatment.

2-(4-((4-Chloro-6-((3',6'-dihydroxy-3-oxospiro [isoindoline-1,9'-xanthen]-2-yl)amino)-1,3,5-triazin-2-yl)amino)benzoyl)-N-phenylhydrazine-1-carbothioamide (PCFH) is prepared for the detection of Hg2+ by hydrogen-induced emission (HIE). In the presence of blood serum, PCFH has a strong fluorescence response to Hg2+ in ethanol/H2O (90/10, v/v), while the fluorescence with other metal ions, including Cu2+, is much weaker. PCFH coordinates better with Hg2+ than Cu2+, which gives rise to specificity of detection. Through spectroscopic techniques and molecular dynamics simulations, the mechanism of HIE reveals that the interactions between polar bonds of PCFH and protein in blood serum via hydrogen bonding can efficiently enhance the specificity and sensitivity of detection. As the results of the interactions, the free rotation of two plenary structures of PCFH linked by C C bonds is restricted, which leads to increased planarity, and the protein destroys the coordination between Cu2+ and PCFH. The development of cells under Hg2+ pollution is monitored, and the concentrations of Hg2+ in deformed and dead cells are 0.47 μM and 0.88 μM respectively. The HIE effects found here will promote new ideas in the design of new types of fluorescence probes for Hg2+ and other metal ions.

A multisite-targeting polymer with the ability of both fluorescence and targeting recognition was successfully synthesized by using fluorescein as the fluorescent group and folic acid as the targeted group. The chemical structure of fluorescent monomer and polymer was characterized and analyzed by FTIR and 1H NMR. The cytotoxicity and biocompatibility of this polymer were characterized by MTT assay and hemolysis rate respectively. The cell viability was 85 % and the hemolysis rate of erythrocyte was only 0.147 % even at the concentration of PFLAC was 10−4 mol/L. The polymer has also been applied to cell imaging for the identification of human colorectal cancer cells. Interestingly, the results show that the polymer was able to enter into the specific cell with an excellent targeting ability.

Free lead and zinc ions are toxic to living cells and environment, we develop a multi-responsive fluorescence probe based on water-soluble double hydrophilic block copolymer. The polymer sensor with Schiff moiety can sensitively, selectively and simultaneously fluorescence probe Zn2+ (green) and Pb2+ (blue) through the different fluorescence color. The linear concentration ranges for Pd2+ and Zn2+ were 0.8–10.0 μM and 0–10.0 μM with the detection limits of 0.7 μM and 0.2 μM, respectively. The probe responding to Na+, Mn2+, Fe2+, Fe3+, Cu2+, Zn2+, Cd2+, Al3+, Cr3+, Co2+, Ni2+, Ag+, Ca2+, K+, Mg2+, Ba2+, Hg2+, and Pb2+ displays almost no significant interference with the assay process. The sensing mechanism of the PSAM probe to Pb2+ and Zn2+ was investigated by Job's plot experiment, 1H NMR analysis and density functional theory (DFT), the results show that the nitrogen atom of CH N and oxygen atom of OH may recognize with ions and the Job's plots for the PSAM complexes demonstrate 1:1 complexation, respectively. To achieve its application, the chemosensor is successfully applied to monitor Pd2+and Zn2+ in tap and lake water samples, its ability to monitor free Pd2+ and Zn2+ ions in living cells or in vivo is also validated by the intracellular imaging.

Graphitic nitrogen-doped hierarchical porous carbon nanosheets for supercapacitor application were derived from an easily obtained and green silk by simultaneous ZnCl2 activation and FeCl3 graphitization at different heating temperatures. By increasing the heating temperature from 700 to 850 °C, the degree of graphitization and BET surface area rose to their highest levels, while the nitrogen doping content was maintained at 2.24 wt%. Carbonized silk at 850 °C displays a nanosheet morphology and a considerable specific surface area (1285.31 m2 g−1), and it was fabricated into a supercapacitor as an electrode material, exhibiting superior electrochemical performance with a high specific capacitance of 178 F g−1 at 0.5 A g−1 and an excellent rate capability (81% capacitance retention ratio even at 20 A g−1) in 1 mol L−1 H2SO4 electrolyte. A symmetric supercapacitor using carbonized silk at 850 °C as the electrodes has an excellent specific energy of 14.33 W h kg−1 at a power density of 251 W kg−1 operated over a wide voltage range of 2.0 V in aqueous neutral Na2SO4 electrolyte.

A study on the cross-linking of fluorinated acrylate and siloxane waterborne polyurethanes was carried out in order to produce a material with improved waterproof property. Trimethylolpropane-tris-(β-N-aziridinyl) propionate was employed as a simple, fast curing and low cost crosslinking agent. It follows that the acquired polyurethane film had the lowest water absorption and highest water contact angles so far among this series of compounds, and has better mechanical/thermal properties once the fluoride acrylic monomer content reaches 8 wt% and polyether modified polydimethylsiloxane content is 10 wt%. Once the crosslinked structure is acquired, the overall performance of the polyurethane films are enhanced, i.e. the water absorption decreases to 3.48% and n-heptane swelling decreases to 1.02%, the hardness reaches 6H and the tensile strength also rises to 33.2 MPa. Such eco-friendly crosslinked polyurethane films with outstanding waterproof property can find various applications in corrosion protection and optoelectronic devices.

We have prepared nitrogen and oxygen enriched hierarchically porous carbon (NOHPC) based on a concept of neutralization reaction. The reactant of KOH and the reaction product of KCl mixed in soybean flour acts as chemical activators and porogens during carbonization, which play different roles to produce the hierarchical porous structure containing macropores, mesopores and micropores. After the investigation of the effect of the reaction pH and carbonization temperature on the structure, the optimized NOHPC with reaction pH at 11.5 and carbonization temperature at 900 °C has a large area (2404.3 m2 g−1), with a high pore volume of 1.31 cm3 g−1, a nitrogen content (0.42%) and an oxygen content (32.1%). When assembling supercapacitors, NOHPC has a extremely large specific capacitance (381 F g−1 at 1 A g−1) and large energy density (20.78–15.42 Wh kg−1), and possesses good rate performance. Particularly, the symmetric supercapacitor assembled based on NOHPC-900-11.5 has a good cycle stability in the voltage range of 0–1.8 V in a two-electrode system with 1 M Na2SO4 as the electrolyte. It is worth noting that when Tetraethylazanium tetrafluoroborate (TEATFB) in propylene carbonate and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (EMIMNTF2) are selected as electrolyte, high energy densities of 31.4 Wh kg−1 and 71.6 Wh kg−1 are achieved. The above results indicate that NOHPC prepared based on neutralization reaction is superior energy storage materials. This work has universal significance in producing high performance porous carbons from biomass.

This work examines the self-collimation effect of silk materials on fluorescence emission/detection. A macroscopic regulation strategy, coupled with meso-reconstruction and meso-functionalization, is adopted to amplify the fluorescence emission of organic fluorescent dyes (i.e., Rhodamine 6G (R6G)) using silk photonic crystal (PC) films. The fluorescence emission can be linearly enhanced or inhibited by a PC as a result of the photonic bandgap coupling with the excitation light and/or emission light. Depending on the design of the silk fluorescence collimator, the emission can reach 49.37 times higher than the control. The silk fluorescence collimator can be applied to achieve significant benefits: for instance, as a humidity sensor, it provides good reproducibility and a sensitivity of 28.50 a.u./% relative humidity, which is 80.78 times higher than the sensitivity of the control, and as a novel curtain, it raises the energy conversion efficiency of the semitransparent dye-sensitized solar cells (DSSCs) by 16%.

From the perspective of mesoscale, the formation mechanism of crystal network structure of supramolecular gel, the influence of structure on macroscopic properties, and the design and control of supramolecular gels are reviewed. Crystal network is a key character of the hierarchical structure of the gel, the formations of the basic and multi-level crystal networks are based on the crystal nucleation and growth. The engineering and controlling of the gel structure can be implemented by various stimuli, such as additives, sonication, seeding and thermodynamic driving force, which leads to a controllable performance of the gel. In addition, the methods of characterizing supramolecular gels are systematically summarized, such as rheology, atomic force microscope, scanning tunnel microscope, scanning electron microscope, transmission electron microscope, polarizing optical microscope, X-ray diffraction (XRD), small-angle X-ray scattering, small angle neutron scattering, nuclear magnetic resonance spectroscopy, dynamic light scattering (DLS), etc. Supramolecular gel performance is determined by the hierarchy mesoscopic structures, which can significantly improve the properties of the material. Four factors can be correlated to the structure and performance of material: topology, correlation length, symmetry/ordering and strength of association of crystal networks. According to the more in-depth understanding of mesoscopic supramolecular gels, the research and development of such a material will be pushed to a new stage.

Although quantum dots (QDs) have remarkable potential application in flexible light emitting diodes (LED), the loss of solvent-protected QDs leads to low quantum yield (QY) and poor stability, severely restricting the development. Flexible QD LEDs (Q-LEDs) with three primary colors were fabricated by mixing CdS/ZnS, CdSe@ZnS/ZnS, and CdSe/CdS QDs with polydimethylsiloxane (PDMS) by in situ hydrosilylation based surface manipulation strategy, which endows the device with highly ultrastable and luminescent performance. The surface manipulation strategy mainly includes the control of solvent dosage, purification times of QDs, concentration of QDs in PDMS, and oxidation on the preparation process of the QDs and PDMS composites. The highest QY of CdSe@ZnS/ZnS-PDMS composite is 82.03%, higher than the QY (80%) of the QD solution. After UV bleaching, organic solvents (acetone, ethanol and water), and heating treatment, the QYs of the QDs and PDMS maintain a high value, manifesting their good stability. Q-LED hybrid light-emitting devices were further fabricated by a molding technique demonstrating satisfied current and thermal stability. Flexible Q-LEDs can be expended to other shapes, such as fibers and blocks, indicating the huge potential of QD-polymer composites for light sources and displays etc.

Silk fibroin (SF) offers great opportunities in manufacturing biocompatible/partially biodegradable devices with environmental benignity and biomedical applications. To obtain active SF devices of next generation, this work is to demonstrate a new functionalization strategy of the mesoscopic functionalization for soft materials. Unlike the atomic functionalization of solid materials, the meso-functionalization is to incorporate meso-dopants, i.e., functional molecules or nanomaterials, quantum dots, into the mesoscopic networks of soft materials. In this work, wool keratin (WK) molecules were adopted as mediating molecules to incorporate gold nanoclusters (AuNCs), into the mesoscopic networks of SF. It follows from our analyses that the β-crystallites between WK and SF molecules establish the binding between WK@AuNCs and the SF networks. The incorporated WK@AuNCs are electron rich and serve as electronically charged nano particles to bridge the growth of Ag filaments in bio-degradable WK@AuNCs-SF memristors. The meso-functionalization can greatly enhance the performance of SF materials and endows them with new functionalities. This can be highlighted by biocompatible/partly degradable WK@AuNCs functionalized SF resistive random-access memories, having the enhanced resistive switching memory performance, and the unique synapse characteristics and the capability of synapse learning compared with neat SF devices, and of great importance in nonvolatile memory, analog circuits, and neuromorphic applications.

In biomedical applications, it is very desirable to monitor the in vivo state of implanted devices, i.e., tracking the location, the state, and the interaction between the implanted devices and cell tissues. To achieve this goal, a generic strategy of soft materials meso-functionalization is presented. This is to acquire silk fibroin (SF) materials with added functions, i.e., in vivo bioimaging/sensing. The functionalization is by 3D materials assembly of functional components, lanthanide(Ln)-doped upconversion nanoparticles (UCNPs) on the mesoscopic scale to acquire upconversion fluorescent emission. To implement the meso-functionalization, the surfaces of UCNPs are modified by the hydroxyl groups (OH) from SiO2 or polyethylene glycol coating layers, which can interact with the carbonyl groups (CO) in SF scaffolds. The functionalized silk scaffolds are further implanted subcutaneously into mice, which allows the silk scaffolds to have fluorescent in vivo bioimaging and other biomedical functions. This material functionalization strategy may lead to the rational design of biomaterials in a more generic way.