Wearable and highly sensitive strain sensors are essential components of electronic skin for future biomonitoring and human machine interfaces. Here we report a low-cost yet efficient strategy to dope polyaniline microparticles into gold nanowire (AuNW) films, leading to 10 times enhancement in conductivity and ∼8 times improvement in sensitivity. Simultaneously, tattoolike wearable sensors could be fabricated simply by a direct "draw-on" strategy with a Chinese penbrush. The stretchability of the sensors could be enhanced from 99.7% to 149.6% by designing curved tattoo with different radius of curvatures. We also demonstrated roller coating method to encapusulate AuNWs sensors, exhibiting excellent water resistibility and durability. Because of improved conductivity of our sensors, they can directly interface with existing wireless circuitry, allowing for fabrication of wireless flexion sensors for a human finger-controlled robotic arm system.

The synthesis of hydrogen peroxide (H2O2) from H2O and O2 by metal-free photocatalysts (e.g., graphitic carbon nitride, C3N4) is a potentially promising approach to generate H2O2. However, the photocatalytic H2O2 generation activity of the pristine C3N4 in pure H2O is poor due to unpropitious rapid charge recombination and unfavorable selectivity. Herein, we report a facile method to boost the photocatalytic H2O2 production by grafting cationic polyethylenimine (PEI) molecules onto C3N4. Experimental results and density functional theory (DFT) calculations demonstrate PEI can tune the local electronic environment of C3N4. The unique intermolecular electronic interaction in PEI/C3N4 not only improves the electron–hole separation but also promotes the two-electron O2 reduction to H2O2 via the sequential two-step single-electron reduction route. With the synergy of improved charge separation and high selectivity of two-electron O2 reduction, PEI/C3N4 exhibits an unexpectedly high H2O2 generation activity of 208.1 μmol g–1 h–1, which is 25-fold higher than that of pristine C3N4. This study establishes a paradigm of tuning the electronic property of C3N4 via functional molecules for boosted photocatalysis activity and selectivity.

new design principles. Nanomaterials, such as carbon nanotubes, [1,3,4,[12][13][14] graphene, [15,16] and metal nanowires [8,9,[17][18][19][20][21][22][23][24] have been recently explored and demonstrated their potentials to flexible TE overcoming shortcoming of current ITObased TE (brittleness, low inferred transmittance, and earth rareness). Despite this potential, it remains challenging to achieve high conductivity and high transparency without deterioration under repeated bending and stretching cycles. In this context, metal mesh/grid is emerging as a promising solution, which achieved exceptionally low-sheet resistance and high optical transparency. [25][26][27] The fabrication of mesh-like electrodes could be achieved by top-down [25][26][27][28] and bottomup [29,30] approaches. Self-assembled meshlike structure have been successfully demonstrated by using silver and gold nanoparticles. [29,30] However, to the best of our knowledge, self-assembled mesh geometry based on 1D nanowire materials has not been reported. Here, we report a simple yet efficient solution-based, equipment-free interfacial self-assembly strategy to fabricate mesh TE (mTE) using ultrathin gold nanowires. Unlike other metal nanomaterials, ultrathin gold nanowires we used possess a serpentine morphology due to its ultrathin width (≈2 nm) and ultrahigh aspect ratio (>10 000). [31][32][33] Briefly, freshly synthesized AuNWs hexane solutions were purified and aged prior to spreading onto air-water interface. During the hexane evaporation, AuNWs could self-assemble into bundles with a mesh-like network. The partial removal of oleyamine ligands during aging may be the reason for the bundle formation. [34] The bundles had a typical thickness of 193.7 ± 67.6 nm and mesh pore sizes varied from 8 μm to 52 μm, depending on 100 random pores at aging time of 12 h. The resulting mesh film is easily transferred to a variety of substrate, exhibiting a sheet resistance of ≈40 times smaller than our previous nonmeshed film [18] under the similar optical transmittance of ≈92%. Moreover, our mesh electrode is patternable and washable with excellent flexibility, which could be directly used for touch screen and flexible circuit of light emitting devices (LEDs). We believe our approach opens a new route to flexible TE for applications in future soft electronic sensors, displays and energy-harvesting devices.Transparent electrodes simultaneously require high electrical conductivity and high optical transparency, which have been achieved with mesh metal structures. However, most currently fabricated micro-and nanoelectronic devices are produced via top-down lithography methods. Here, a bottomup self-assembly approach to fabricate mesh electrode using ultrathin gold nanowires (AuNWs) at the air/water interface is reported. Slow partial ligand removal during the aging process is the key for the formation of such self-assembled mesh structures. The resulting mesh film has a typical mesh pore size of 8-52 μm, with a sheet resistance of ≈40 times smaller than our pr...

The phase behavior of a long hydrophobic chain A-B-type silicone surfactant, Me 3 SiO-(Me 2 SiO) m-2 -Me 2 -SiCH 2 CH 2 CH 2 -O-(CH 2 CH 2 O) n H (Si m C 3 EO n ), in water was investigated by phase study and small-angle X-ray scattering (SAXS). The types of liquid crystals or self-organized structures are highly dependent on both EO-chain (n) and poly(dimethylsiloxane)-chain (m) lengths or the volume ratio of the EO chain to the total surfactant, nV EO /V S , which is related to the classical Griffin's HLB value. Reverse discontinuous cubic phase (I 2 ) for Si 14 C 3 EO 7.8 and Si 25 C 3 EO 7.8,12.2,15.8 , reverse hexagonal phase (H 2 ) for Si 14 C 3 EO 12 , lamellar (L R ) phase for Si 14 C 3 EO 15.8 and Si 25 C 3 EO 51.6 , and hexagonal (H 1 ) and discontinuous cubic (I 1 ) phases for Si 5.8 C 3 -EO 36.6,51.6 are formed. Hence, both hydrophobic and hydrophilic chains affect the surfactant layer curvature, but in an opposite way. On the other hand, the effective cross-sectional area per surfactant at the hydrophobic surface of self-organized structures, a S , increases with increasing m (or n) at constant n (or m). a S is related to the amphiphilicity of surfactant (surfactant size). Since the surfactant layer curvature changes from positive to negative with increasing m at constant n, the l eff /l max decreases with m, where l eff is the effective hydrophobicchain length and l max is the length of the chain in its fully extended form. Namely, the entropy loss of a long hydrophobic chain would be largely increased when it is stretched, and thus, long hydrophobic chain tends to be in a shrunk-bulky state. This causes the expansion of a S and the change in the surfactant layer curvature from positive to negative. In a similar mechanism, a S increases with increasing the EO-chain length, n, but the surfactant layer curvature changes from negative to positive.