A broadband all-fiber integrated graphene photodetector with CNT-enhanced responsivity.

Carbon-based nanomaterials such as carbon nanotubes (CNTs) and graphene have great potential for high-performance all-carbon photodetectors due to their unique optical and electronic properties. Here, we assemble a hybrid CNT/graphene film prepared by depositing CNTs on a single layer graphene with a side-polished optical fiber to achieve a novel all-fiber integrated photodetector. Because CNTs strongly enhanced the interaction between graphene and the fiber mode, the photodetector shows an extra-high photoresponsivity over the visible and infrared region. Especially at 1550 nm, the photoresponsivity is found to be ∼1.48 × 105 A W-1, which is 6.5 times larger than those of photodetectors without CNTs. These findings provide a highly versatile, reproducible, and low-cost platform to integrate novel zero-, one-, and two-dimensional materials into optical fibers and deliver more sophisticated functionalities.

A broadband and low-power light-control-light effect in a fiber-optic nano-optomechanical system.

The coupling of the optical and mechanical degrees of freedom using optical force in nano-devices offers a novel mechanism to implement all-optical signal processing. However, the ultra-weak optical force requires a high pump optical power to realize all-optical processing. For such devices, it is still challenging to lower the pump power and simultaneously broaden the bandwidth of the signal light under processing. In this work, a simple and cost-effective optomechanical scheme was demonstrated that was capable of achieving a broadband (208 nm) and micro-Watt (∼624.13 µW) light-control-light effect driven by a relatively weak optical force (∼3 pN). In the scheme, a tapered nanofiber (TNF) was evanescently coupled with a substrate, allowing the pump light guided in the TNF to generate a strong transverse optical force for the light-control-light effect. Additionally, thanks to the low stiffness (5.44 fN nm-1) of the TNF, the light-control-light scheme also provided a simple method to measure the static weak optical force with a minimum detectable optical force down to 380.8 fN. The results establish TNF as a cost-effective scheme to break the limitation of the modulation wavelength bandwidth (MWB) at a low pump power and show that the TNF-optic optomechanical system can be well described as a harmonic oscillator.

The effect of nanoscale friction of mesoporous carbon supported ionic liquids on the mass transfer of CO2 adsorption.

Supported ionic liquids (ILs) are attractive alternatives for CO2 capture and the thickness of supported IL films plays a critical role in the CO2 mass transfer rate. However, the dependence of CO2 uptake on the IL film thickness differs as the system varies. In this work, atomic force microscopy (AFM) is employed to probe the 'nanofriction coefficient' to characterize the mobility of ILs at the solid interface, in which, the smaller the nanofriction coefficient, the faster are the ionic mobility and CO2 mass transfer. A monotonic and almost linear relationship for supported IL films is obtained between the resistance of CO2 mass transfer (1/k) and the nanofriction coefficient (µ), avoiding the controversy over the effect of supported IL film thickness on CO2 adsorption. The enhanced mass transfer of CO2 adsorption at IL-solid interfaces is observed at smaller resistance 1/k and friction coefficient µ. The low-friction driven local mobility (diffusion) of ILs at solid interfaces is enhanced, promoting the exchange mixing of the ILs adsorbing CO2 with the 'blank-clean' ions of the ILs, and thus accelerating the CO2 mass transfer. The proposed correlation links the nanoscale friction with the mass transfer of CO2 adsorption, providing a fresh view on the design of ultra-low frictional supported ILs for enhanced CO2 capture and separation processes.

Pollution, demographic, and public willingness to participate in environment protection in China-a study based on micro-survey data.

Previous study found out that Chinese household have a higher awareness of environmental protection but less positive initiative to protect the environment. With the increasing Chinese income, higher education, and changing environment state, public awareness and behavior on environment protection are changing. This paper tries to find out the current public willingness to participate in environment protection, by using the latest data from China Household Finance Survey (CHFS) which is investigated in 2017 that covered 31 provinces with a sample of more than 40 thousand households. Besides, logit regression model is adopted to find out the impact of pollution and household demographic on environment protection behavior. The results show that around 71.6% of surveyed households have willingness to pay for the environment protection. Rural residents and higher educated individuals are more likely to participate in environment protection. However, things are different if they face different degrees of pollution. Results can be explained with China's current economic situation and would have some implications for future study on China's public willingness to pay for the environment.

Nanofriction of Graphene/Ionic Liquid-Infused Block Copolymer Homoporous Membranes.

We have infused graphene/ionic liquid into block copolymer homoporous membranes (HOMEs), which have highly ordered uniform cylindrical nanopores, to form compact, dense, and continuous graphene/ionic liquid (Gr/IL) lubricating layers at interfaces, enabling a reduction in the friction coefficient. Raman and XPS analyses, confirmed the parallel alignment of the cation of ILs on graphene by the π-π stacking interaction of the imidazolium ring with the graphene layer. This alignment loosens the lattice spacing of Gr in Gr/ILs, leading to a larger lattice spacing of 0.36 nm in Gr of Gr/ILs hybrids than the pristine Gr (0.33 nm). The loose graphene layers, which are caused by the coexistence of graphene and ILs, would make the sliding easier, and favor the lubrication. An increase in the friction coefficient was observed on ILs-infused block copolymer HOMEs, as compared to Gr/ILs-infused ones, due to the absence of Gr and the unstably formed ILs film. Gr/ILs-infused block copolymer HOMEs also exhibit much smaller residual indentation depth and peak indentation depth in comparison with ILs-infused ones. This indicates that the existence of stably supported Gr/ILs hybrid liquid films aids the reduction of the friction coefficient by preventing the thinning of the lubricant layer and exposure of the underlying block copolymer HOMEs.