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A flexible carbon nanofiber film with high conductivity was prepared by electrospinning, and then Cu was uniformly deposited on the fiber film by pulse electrodeposition to prepare Cu nanocrystal/carbon nanofiber film. Cu@PtCu/carbon nanofiber (Cu@PtCu/CNF) catalytic films were synthesized by in-situ substitution reduction. The Cu@PtCu/CNF catalytic film solves the problem of uneven activity of the catalytic layer and can be directly used as the catalytic layer. The morphology and structure were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Electrochemical test results show that the Cu@PtCu/CNF catalytic films obtained at the chloroplatinic acid concentration of 0.5 mg·mL

A novel oxygen reduction reaction (ORR) electrocatalyst silver@platinum-cobalt-rGO nanoflower (Ag@PtCo-rGO NFs) is prepared by hydrothermal reduction method. The formation of silver chloride likes elm leaf microstructure in the reaction process, performing as a template. The Ag@PtCo-rGO NFs exhibit excellent electrocatalytic activity, whose specific activity is 9 times higher than that of commercial Pt/C. More importantly, Ag@PtCo-rGO NFs demonstrate excellent durability than JM Pt/C for ORR in acid media, as evidenced by accelerated durability test after 40,000 cycles. These excellent performances can be attributed to the special structure, atomic steps and synergistic effect between Pt, Ag and Co. The density functional theory calculation shows that Ag@PtCo has the best activity, which is related to the transition state for O–O bond. This work proposes a promising pathway for the synthesis of surfactant-free nanoflowers structure catalysts with high catalytic performance and low cost.

For the study, we prepared a low grain boundary three-dimensional CH3NH3PbI3 crystal (3D-MAPbI3) on TiO2 nanoarrays by inhibition of ammonium iodide and discussed the formation mechanism of the crystal. Based on the 3D-MAPbI3 crystal, solar cells showed modified performance with a power conversion efficiency (PCE) of up to 19.3%, which increases by 36.8% in contrast to the counterparts. We studied the internal photocurrent conversion process. The highest external quantum efficiency is up to 92%, and the electron injection efficiency is remarkably facilitated where the injection time decreases by 37.8% compared to the control group. In addition, based on 3D-MAPbI3, solar cells showed excellent air stability, which possesses 78.3% of the initial PCE, even though they were exposed to air for 30 days. Our results demonstrate a promising approach for the fabrication of perovskite solar cells with high efficiency and stability.

Shape-tunable PtAg nanocatalysts including PtAg nanoflowers (NFs) and PtAg nanowires (NWs) are prepared by a facile hydrothermal reduction method, via adjusting the precursor ratio of Pt/Ag and subsequent UV-irradiation. Physicochemical characterizations reveal that the as-prepared catalysts have a porous structure, which forms from the conversion of AgCl to Ag nanoparticles. These features favor both oxygen mass transfer and accessibility of active sites. The as-prepared Pt1Ag4 NWs exhibit superior catalytic performances for ORR. The mass activity of Pt1Ag4 NWs is 11.4 times higher than that of 20% Pt/C. More important, the electrochemically active surface area (ECSA) of Pt1Ag4 NWs is 2.5 times larger than that of commercial Pt/C.

A novel platinum-palladium/carbon nanowires (PtPd/CNWs) catalysts are successfully prepared by electrospinning for the oxygen reduction reaction (ORR). The prepared PtPd/CNWs catalysts exist in the form of membrane, which can be directly applied as catalyst layer in membrane electrode assembly. The ORR activity of binary PtPd/CNWs catalysts are enhanced significantly in comparison to the ternary platinum-palladium-gold/carbon nanowires (PtPdAu/CNWs) catalysts and 20% Pt/C. Here, the gold in PtPdAu/CNWs mainly exists in larger gold nanoparticles rather than in the form of ternary alloy with Pt, Pd. The mass activity and special activity of PtPd/CNWs are 4.230 times and 4.225 times than that of 20% Pt/C, respectively. Moreover, the electrochemical active surface areas (ECSAs) of PtPd/CNWs catalysts almost keep constant after 5000 potential cycling, whereas 20% Pt/C drops almost 40% after 5000 potential cycling.

To enhance the activity and durability of platinum (Pt) or platinum-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), fabrication of low-cost platinum catalysts with durable structure is necessary. Here, a series of one-dimensional (1D) platinum-gold/titanium dioxide nanowires (PtAu/TiO2 NWs) catalysts with different Pt/Au/Ti ratios were synthesized by electrospinning, and the microstructure as well as its electrochemical properties for ORR were investigated. The results illustrate that PtAu/TiO2 NWs indicate a parabolic-type ORR performance as a function of compositions. The optimized Pt1Au1/(TiO2)1 NWs exhibited 4.19 times in mass activity and 2.82 times in SA when compared with commercial Pt on carbon catalyst (20% Pt/C). In addition, the stability test shows that the ECSA of Pt1Au1/(TiO2)1 NWs present almost 20% decrease, while the 20%Pt/C drops more than 40% at the same condition. The extraordinary activity of Pt1Au1/(TiO2)1 NWs could be attributed to the synergistic effect of TiO2 and the durability attributed to Au and C skin. The nanowires with larger specific area show that the Pt electronic structure can be changed by the neighbouring TiO2, further decreasing the d-band gap to enhance catalytic activity.

Recent discoveries have found that pressure dependence in quantum dots (QDs) doped in epoxy resin will have an obvious influence on the intensity of its photoluminescence (PL). Therefore, it is possible for us to monitor cracks due to the concentration of stress near the cracks when the force is loaded and the residual stress alongside the cracks after the force is unloaded. The measurement of the crack length has a wide range which can vary from dozens of microns to several centimetres. Further experiments were carried out to validate that it is the combination of both the abrupt change of stress in substrate and the interaction between the matrix and QDs that realizes the PL enhancement region near the cracks.

The structural applications of quantum dots (QDs) can be artificially realized through the preparation of QDs-based structural materials, which have unique characteristics of photoluminescence (PL) in response to mechanical deformation, via the dispersion of quantum dots in various materials, including polymers and plastics. A QDs-based composite consisting of CdSe@ZnS core–shell QDs and a bisphenol-A type epoxy resin has been prepared by mixing a solution of CdSe@ZnS core–shell QDs in chloroform with bisphenol-A type epoxy resin and modified amine at room temperature. The tensile deformation of the tensile specimens made from the QDs-based composite causes a significant change in the PL intensity for large engineering strains, and there is no observable strain-induced shift of the wavelength corresponding to the maximum PL intensity. Two major modes are observed for the temporal variation of the PL intensity of the QDs-based composite coated on AA 7009 tensile specimens under cyclic loading and unloading of small strains. One exhibits in-phase characteristics with strain, and the other exhibits antiphase characteristics with strain. The variation of the PL intensity of the QDs-based composite with tensile strain suggests that there exists strain-dependent photoluminescence, which determines the PL characteristics of the CdSe@ZnS core–shell QDs in the bisphenol-A type epoxy under the irradiation of ultraviolet light. The experimental results demonstrate the potential of developing sensitive opto-mechanical devices from QDs-based composites.

Pt-Au nanoparticles supported on carbon black (PtAu/CBx) are produced by a facile chemical reduction method and subsequent heat treatment. In this paper, the effects of heat treatment temperature on structure and electrochemical properties are investigated. A series of catalysts, including PtAu/CB, PtAu/CB400 and PtAu/CB600, with different particle size are synthesized. The particle size of PtAu/CB600 is slightly larger than that of PtAu/CB400 and PtAu/CB, but the electrochemical performance of PtAu/CB600 is the best due to more active sites available in PtAu/CB600. Moreover, the durability of PtAu/CB600 and commercial Pt/C is researched in acidic media. After 5000 cycles accelerated durability test, it can be seen from CV and LSV that PtAu/CB600 shows better stability. Therefore, the better activity and stability of PtAu/CB600 can be ascribed to the ordered structure and the synergistic effect of Pt and Au.

To avoid the loss and accident caused by energy equipment failure, structural integrity monitoring requires precise sensors for measurement of stress and strain. Quantum dots (QDs)-epoxy resin composite shows variation of photoluminescence (PL) intensity under stretching. This paper presents three different phenomena of PL intensity during cyclic stretching. QDs-Epoxy Resin blank stretching and ANSYS calculation provide PL intensity tendency with strain transforming. Continuous cyclic loading after the PL intensity change becomes stable, illustrating a non-synchronized strain between metal and coating. The synchronous strain can be achieved in a wide application with the development of sensitive optical stress-strain sensors via optimization and characterization of QDs-Epoxy Resin.

Due to that the spectra of CdSe/ZnS core/shell nanocrystals showed a wavelength shift when under external pressures, researches are conducted to design a wavelength shift-based strain or stress gauge. However, the spectrum's shift can only be subtly sensitive when the pressure applied to nanocrystals reaches GPa, which makes the gauge hard to be applied to practice. In this paper, it was found that the photoluminescence(PL) intensity of CdSe/ZnS core/shell quantum dots (QDs)epoxy resin composites changes significantly with strain. Meanwhile, the changes remains stable after 3-5 cycles. We coated the QDs-epoxy resin composites on the surface of metal tensile sample, the PL intensity and strain changes synchronously. In addition, it has been successfully proved that the variation of QDs’ concentrations along with the strain is the main reason for the photoluminescence intensity changing. This research has shown the possibility that this kind of nanocomposite can be designed as a new strain gauge to quantitatively detect stress or strain in-situ by being coated on the structure surface.

The “ball-on-film” template is used to construct concentric rings on the surface of PMMA-QDs (polymethyl methacrylate – quantum dots) nanocomposite films via the evaporation of pure chloroform droplets, which are confined by a steel ball. The concentric rings consist of QDs, as revealed by the fluorescence images of the concentric rings. The photoluminescence intensity of the concentric rings increases with the increase of the distance to the ball center, suggesting that the amount of QDs accumulated around the contact line at individual stick state increases with the increase of the distance to the ball center. Both the wavelength and cross-sectional area (width) of the concentric rings increase approximately linearly with increasing distance to the ball center, independent of the ball size, the film thickness and the QDs concentration. For the PMMA-QDs nanocomposite films prepared from the same QDs concentration in chloroform, the thicker the PMMA-QDs nanocomposite film, the larger the wavelength for the same distance to the ball center. The effect of confinement of two steel balls on the surface patterns over the PMMA-QDs nanocomposite films is studied via a template of “two spheres on film”. Symmetric surface patterns are formed. There exist two types of featureless zone between the two balls, depending on the distance between the two balls: one is the inner featureless zone and the other is the outer featureless zone. The size of both featureless zones increases with the increase of the ball distance.

A visualization method for monitoring minor metal crack propagation is presented in this paper. Through CdS@ZnS core-shell quantum dots (QDs) enhanced emission of photoluminescence (PL), this crack detection method provides a visualization signal in real time and through a noncontact fashion. The crack of the CdS@ZnS core-shell QDs-epoxy resin kept a synchronous propagation with the metal crack. Detection of the tip growth in the film layers demonstrated that the actual crack propagation on the metal surface could be deduced from the tips in the film layers. The fluorescence peak tended to increase along the crack from the initial opening to the tip. Crack width as small as 10 μm can be detected with a precision of 0.1 μm and the minimum crack tip width of the QDs-epoxy resin was measured as 0.72 μm.