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Hydrogels are widely used in fields such as drug delivery, tissue regeneration, soft robotics and flexible smart electronic devices, yet their application is often limited by unsatisfactory mechanical behaviors. Among the various improvement strategies, double network (DN) hydrogels from synthetic polymers demonstrated impressive mechanical properties, while those from natural polymers were usually inferior. Here, a novel DN hydrogel composed fully of natural polymers exhibiting remarkable mechanical properties and conductivity is prepared by simply soaking a virgin gellan gum/gelatin composite hydrogel in a mixed solution of Na2SO4 and (NH4)2SO4. This hydrogel exhibits a tunable Young's modulus (0.08 to 42.6 MPa), good fracture stress (0.05 to 7.5 MPa), good fracture stretch (1.4 to 7.1), high fracture toughness (up to 27.7 kJ m−2), and high ionic conductivity (up to 11.4 S m−1 at f = 1 kHz). The improvement in the mechanical properties of the DN gel is attributed to the chain-entanglement crosslinking points introduced by SO42− in the gelatin network and the electrostatic interaction crosslinking points introduced by Na+ in the gellan gum network. The high ionic conductivity of the DN gel is attributed to the infiltration of the DN gel in a salt solution of high concentration. The developed gellan gum/gelatin DN hydrogel has shown a new pathway towards strengthening natural-polymer-based DN hydrogels and towards potential applications in biomedical engineering and flexible electronic devices.

Nowadays, several approaches are being suggested to endow hydrogels with improved mechanical properties for practical applications as cartilage and skin replacements, soft electronics, and actuators. However, it remains a challenge to develop DN gels with both high fracture toughness and fracture stretch. Here, we introduce (bio)polyelectrolyte complexes (PECs) consisting of gelatin and κ-carrageenan as the first brittle network and covalently crosslinked polyacrylamide (PAAm) as the second stretchable network to fabricate a highly stretchable and notch-insensitive gelatin/κ-carrageenan/PAAm hydrogel. The unprecedented high stretchability (∼51.7) is ascribed to the reduction of stress concentration and defects in the network structure through the fracture of the PEC gel. In addition, a high fracture toughness (∼16053.34 J m-2) is achieved by effective energy transfer between the PECs and PAAm gel due to their covalent crosslinking, and efficient energy dissipation through destroying inter- and intramolecular interactions in the PEC gel.

Highly ordered LaTb x O y :Eu3+ nanowire arrays have been synthesised in anodic aluminium oxide template by chemical co-deposition at negative pressure suction, it is amorphous and with homogeneous morphologies. There are two peaks at 619 and 704 nm with excitation wavelength of 394 nm, which have red shift slightly relative to the 5D0–2F2 and 5D0–7F4 energy level transition of Eu3+, and Tb3+ exhibits strong fluorescence enhancement and sensitisation in LaTb x O y :Eu3+ nanowire arrays with the existence of La3+. The fluorescence intensity of LaTb x O y :Eu3+ nanowire arrays is related to the doping concentration of Eu3+ ion. When the doping concentration of Eu3+ is 8%, the fluorescence intensity reaches a maximum, and remarkably decreases at higher concentrations.

Ultra-long YCe x O y :Eu 3+ nanowire arrays(NWAs) have been synthesized in anodic aluminum oxide (AAO) templates by chemical co-deposition at negative pressure suction, which are amorphous, and possess precise dimension and homogeneous morphologies. The SEM, TEM, XRD and EDS were employed to investigate the morphology, structure and elemental composition of YCe x O y :Eu 3+ NWAs. The fluorescence properties of the YCe x O y :Eu 3+ NWAs were measured by fluorescence spectrometer (PerkinElmer LS-55) using Xenon discharge lamp as the excitation light source. There are two emission peaks at 615 nm and 702 nm with excitation wavelength of 394 nm, which corresponds to the 5 D 0 - 2 F 2 and 5 D 0 - 7 F 4 energy level transition of Eu 3+ , respectively. The fluorescence intensity of YCe x O y :Eu 3+ NWAs is related to the doping concentration of Eu 3+ ion, which reaches a maximum with doping concentration of Eu 3+ at 8%, and remarkably decreases at higher concentrations. Ce 3+ ion dominates the fluorescence activation in YCe x O y :Eu 3+ NWAs.

Combining a hydrophobic interaction crosslinked curdlan as the first network and hydrophobic interaction crosslinked polyacrylamide as the second network, we have fabricated a curdlan/HPAAm double network (DN) hydrogel using a one-pot method. The resulting DN hydrogel exhibited good mechanical properties, i.e. an elastic modulus of 103 kPa, a tensile fracture strength of 0.81 MPa, a tensile stretch of 25.3 and a compressive stress of 62.5 MPa when the compressive strain increased up to 99%. The DN gel could withstand ten compression tests under 90% compressive strain without observable damage. The DN gel demonstrated 84% stiffness recovery and 97% toughness recovery after the deformed samples were relaxed and stored at 95 °C for 4 h. The stiffness and fracture stress of the DN gel were enhanced after sterilization treatment at 120 °C. Furthermore, the gels exhibited 52% self-healing of fracture stretch after the samples were cut and brought into contact at 95 °C for 4 h. The self-recovery and self-healing properties of the DN gel both originated from the first curdlan network via the reformation of hydrophobic interactions and the second HPAAm network via reformation of the broken hydrophobic associations.

As a kind of typical soft and wet material, hydrogel has been increasingly investigated as another way to develop flexible electronics. However, the traditional hydrogel with poor strain and strength performance cannot meet the requirements for stretchable electronics; fabricating a stretchable hydrogel with balanced tensile strength, toughness, and conductivity is still a big challenge. Herein, a new type of physically cross-linked hydrogel with poly(acrylamide-co-acrylic acid)-Fe3+ and chitosan-SO42- dual ionic networks via facile free radical polymerization and soaking processes is developed to fabricate excellent high-performance flexible sensors. The abundant Fe3+ and SO42- ions in the hydrogel can not only construct tough and strong dual ionic networks but also give the hydrogel high conductivity. Consequently, the optimal hydrogel possesses high tensile strength (∼5.1 MPa), large strain capacity (∼1225%), elasticity (∼1.13 MPa), high toughness (∼32.1 MJ/m3), and high conductivity (3.04 S/m at f = 0.1M), as well as rapid self-recovery property. Furthermore, the hydrogel conductor has high stretching sensitivity with a gauge factor of 6.0 at strain of 700% and was able to detect conventional motions of the human body such as the motions of the knuckle, speaking, and swallowing, which indicates that our ionic conductive hydrogels can be used to fabricate excellent high-performance flexible sensors.

The effects of molecular weight on the thermal degradation behavior of poly(α-methyl styrene) (PAMS) was investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and thermogravimetric analysis (TGA). The Py-GC/MS analysis results showed that the degradation of PAMS with different molecular weights in nitrogen produced only the monomer, alpha-methylstyrene. The TGA results showed a pronounced reduction in the decomposition temperature with increasing molecular weight. The degradation kinetic parameters, calculated by the Kissinger and the Coats–Redfern methods, further revealed that the activation energy and the pre-exponential factor decreased with increasing molecular weight. Most importantly, the degradation order of the PAMS in nitrogen remained around 1, independent of the molecular weight, suggesting the maintenance of the depolymerization mechanism. All the above results provided an insight into the effects of molecular weight on the thermal degradation behavior of PAMS.

In this work, we have successfully synthesized ultrasmall Cu2O nanocrystals with uniform sizes through a solution-based method. By virtue of the ideal Cu2O building blocks, 2D or 3D Cu2O superstructures can be easily achieved by tailoring the assembly process. The results indicate that diethyl carbonate (DEC) plays a crucial role for controlled self-assembly of Cu2O nanoparticles into a range of superstructures. Interestingly, the aggregative growths of Cu2O nanocrystals in the self-assembly process are accompanied by oriented attachment and Ostwald ripening. Furthermore, Cu2O and Cu2O–Au 3D colloidal spheres can be also obtained by an emulsion-based bottom-up self-assembly strategy. The results show that, compared with pure Cu2O nanospheres, the as-obtained Cu2O–Au nanospheres exhibit remarkable photocatalytic activities in the photodegradation of methyl orange (MO).

High quantum efficiencies and low current thresholds are important properties for all classes of semiconductor light emitting devices (LEDs), including nanoscale emitters based on single wall carbon nanotubes (SWNTs). Among the various configurations that can be considered in SWNT LEDs, two terminal geometries with asymmetric metal contacts offer the simplest solution. In this paper, we study, experimentally and theoretically, the mechanisms of electroluminescence in devices that adopt this design and incorporate perfectly aligned, horizontal arrays of individual SWNTs. The results suggest that exciton mediated electron-hole recombination near the lower work-function contact is the dominant source of photon emission. High current thresholds for electroluminescence in these devices result from diffusion and quenching of excitons near the metal contact.

Transparent and conducting zirconium-doped zinc oxide films have been prepared by radio frequency magnetron sputtering at room temperature. The ZrO2 content in the target is varied from 0 to 10 wt.%. The films are polycrystalline with a hexagonal structure and a preferred orientation along the c axis. As the ZrO2 content increases, the crystallinity and conductivity of the film are initially improved and then both show deterioration. Zr atoms mainly substitute Zn atoms when the ZrO2 content are 3 and 5 wt.%, but tend to cluster into grain boundaries at higher contents. The lowest resistivity achieved is 2.07 × 10− 3 Ω cm with the ZrO2 content of 5 wt.% with a Hall mobility of 16 cm2 V− 1 s− 1 and a carrier concentration of 1.95 × 1020 cm− 3. All the films present a high transmittance of above 90% in the visible range. The optical band gap depends on the carrier concentration, and the value is larger at higher carrier concentration.

We proposed a general route to MoS2 hierarchical hollow cages, in which abundant hollow cages with various well-defined, novel geometrical morphologies were fabricated via a self-assembly coupled with surfactant/molybdate composite precursor crystal templating process based on the Kirkendall Effect. The in situ formed surfactant/molybdate composite precursor crystals with cubic structures, which are cooperatively assembled by periodic Mo oxo anion and tetrabutylammonium cation, play crucial roles as both the Mo source and the template in the formation of MoS2 hierarchical hollow cages. Various morphologies of the surfactant/molybdate composite precursor crystals were controllably synthesized through a methodical tuning of the habit and the degree of branching of precursor crystals by varying the SCN− concentration and surfactant concentration.

A new transparent conducting oxide (TCO) film with low resistivity and high transmittance in the visible range, molybdenum-doped zinc oxide (MZO), was successfully prepared by RF magnetron sputtering method on glass substrates at room temperature. The structural, electrical, and optical properties as a function of film thickness were investigated. All the samples have a preferred orientation with the (0 0 2) planes parallel to the substrates. The resistivity initially decreases and then shows an increase with the increase of the film thickness. When the thickness is 400 nm, the film has its best crystallinity and lowest resistivity 9.2 × 10 −4 Ω cm with a Hall mobility of 30 cm 2 V −1 s −1 and a carrier concentration of 2.3 × 10 20 cm −3 . The average transmittance in the visible range exceeds 84% for all thickness films.

ZnO nanodisk arrays have been prepared by utilizing cooperative surface assembly of surfactants and inorganic species at the solid–liquid interfaces under the mild condition. Photoluminescence measurement showed that the obtained ZnO nanodisk arrays exhibit new optical property comparing to the previous results of diverse ZnO nanostructures. Such nanostructures are expected to find more applications employing their optical and electrical properties.

Tin-doped indium-oxide (ITO) and Al-doped zinc oxide (AZO) films were fabricated by reactive evaporation and rf magnetron sputtering. The average optical transmittance ( λ : 400–800 nm) reached 95% and the sheet resistance was as low as 30 Ω/□. Organic light-emitting devices (LEDs) were fabricated with ITO and AZO transparent films as anode and poly (1,4-phenylene vinylene) (PPV) or tris(8-hydroxyquinoline) aluminum (Alq 3 ) as luminescence layer. EL and PL spectra, current–voltage and brightness–voltage data were analyzed. It is revealed that the turn-on voltage of the devices was less than 20 V and the carrier injection was consistent with the tunneling theory. Degradation of current with time at a given external voltage was obtained and discussed.

Indium tin oxide (ITO) films were deposited on water-cooled polypropylene adipate (PPA) substrate using bias RF magnetron sputtering from a ceramic target composed of In 2 O 3 (90%)+SnO 2 (10%). Good polycrystalline-structured ITO films with a low electrical resistivity of 6.3×10 −4 Ω cm have been obtained by applying a negative bias of about −40 V to the substrate at a water-cooled substrate temperature (18±2°C). The visible transmittance of all obtained films was over 80% and in the wavelength range of 400–550 nm, the transmittances increase with increasing the negative bias. X-ray diffraction spectra revealed that all the films oriented preferably with [222] direction and [400] diffraction peak decreased with increasing the negative bias. Both the X-ray diffraction spectra and atomic force microscope (AFM) measurement suggested that the average crystalline size, as well as the conductivity have a maximum value at the bias of about −40 V. The influences of argon pressure and the proportion of SnO 2 on the conductivity of the films were also studied. The optimum argon pressure is 0.5–1 Pa, and the proper content of SnO 2 is 7.5–10 wt.%.

Good transparent conducting indium tin oxide films with good adherence were deposited on water-cooled polypropylene adipate substrate using bias r.f. magnetron sputtering. The films with resistivity as low as 6.3×10 −4 Ω cm and transmittance over 80% have been obtained by adjusting the bias voltage. It was observed that the structural, electrical and optical properties of the films depend on the bias voltage applied to substrate table.

Recent studies and device demonstrations indicate that horizontally aligned arrays of linearly configured single-walled carbon nanotubes (SWNTs) can serve as an effective thin film semiconductor material, suitable for scalable use in high-performance transistors. This paper presents the results of systematic investigations of the dependence of device properties on channel length, to reveal the role of channel and contact resistance in the operation. The results indicate that, for the range of channel lengths and SWNT diameters studied here, source and drain contacts of Pd yield transistors with effectively Ohmic contacts that exhibit negligible dependence of their resistances on gate voltage. For devices that use Au, modulation of the resistance of the contacts represents a significant contribution to the response. Extracted values of the mobilities of the semiconducting SWNTs and the contact resistances associated with metallic and semiconducting SWNTs are consistent with previous reports on single tube test structures.

Micrometer scaled MoS2 hierarchical hollow cubic cages assembled by bilayers can be synthesized via a one-step self-assembly coupled with intermediate crystal templating process without any surfactant, in which the intermediate K2NaMoO3F3 crystal formed in-situ and then served as the self-sacrificed template based on the Kirkendall Effect; The MoS2 hierarchical hollow cubic cages were employed for electrochemical hydrogen storage with a high capacity of 375 mAh g(-1) due to the more active edges exposing on the upright-standing nanoplates.