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TiO2-red phosphorus/C nanofibers (TiO2-RP/CN) have been synthesized via electrospinning and then annealed with red phosphorus sublimation. Benefiting from the high electronic/ionic conductivity and robust stability of the unique structure, the TiO2-RP/CN show high reversible capacities, as well as an outstanding cycling ability. In K half cells, the capacity decay of the TiO2-RP/CN electrode mainly occurs in the first few cycles, and at 0.05 A g−1 it delivers a high specific capacity of 257.8 mA h g−1 after 500 cycles. K full cells were fabricated; these are well-matched with PTCDA (perylene-3,4,9,10-tetracarboxylic dianhydride) and also exhibited a good electrochemical performance (62 mA h g−1 after 100 cycles). Therefore, the TiO2-RP/CN are potential anode materials for use in K-ion batteries.

There are only a handful of reports on indium sulfide (In2S3) in the electrochemical energy storage field without a clear electrochemical reaction mechanism. In this work, a simple electrospinning method has been used to synthesize In2S3/C nanofibers for the first time. In lithium-ion batteries (LIBs), the In2S3/C nanofiber electrode can not only deliver a high initial reversible specific capacity of 696.4 mA h g−1 at 50 mA g−1, but also shows ultra-long cycle life with a capacity retention of 80.5% after 600 cycles at 1000 mA g−1. In sodium-ion batteries (SIBs), the In2S3/C nanofibers electrode can exhibit a high initial reversible specific capacity (393.7 mA h g−1 at 50 mA g−1) and excellent cycling performance with a high capacity retention of 97.3% after 300 cycles at 1000 mA g−1. The excellent electrochemical properties mainly benefited from In2S3 being encapsulated by a carbon matrix, which buffers the volume expansion and significantly improves the conductivity of the composite. Furthermore, the structural evolution of In2S3 during the first lithiation/delithiation and sodiation/desodiation processes has been illustrated by ex situ XRD. The results confirm that the reaction mechanism of In2S3 in both LIBs and SIBs can be summarized as conversion reactions and alloying reactions, which provide theoretical support for the development of In2S3 in the field of electrochemistry.

New oxygen and pressure sensitive paints (PSPs) with four-arm polymeric structures were prepared by using a kind of controlled living polymerizations – atom transfer radical polymerization (ATRP). The polymers composing of poly(isobutyl methacrylate)-co-poly(trifluoroethyl methacrylate)s (PolyIBMA-co-PolyTFEM)s act as the matrices for the platinum porphyrin-based phosphorescence probes, which were copolymerized in the matrices. The polymers were characterized by using 1H NMR, 19F NMR, and GPC to demonstrate their successful preparation. The influence of polymer structures on sensing activity including the sensitivity and response time to oxygen and/or pressure was investigated. Results showed that copolymers with suitable compositions (herein P3) can have highest sensitivity. Polymer structure’s influence on response time to oxygen was also investigated. For increasing the polymer’s surface area for further improving sensing sensitivity, electrospinning method was used for preparing films with micro-spherical or fibrous structures. The morphologies of electrospinning coated films were observed by SEM. Results showed that electrospinning coated films can respond much better to oxygen and pressure than their corresponding sprayed plates. This is the first time to apply the controlled living polymerization approach to prepare PSPs with multi-arm structures, which will broaden the PSP functional materials’ design strategy.

Polymeric microfibers, particularly the fluorinated copolymers’ fibers, are promising functional materials for photoelectric devices, sensing, and energy storage due to their various surface characteristics. However, to obtain the high fluorine content copolymer-based fibers with considerable uniformity is likely to be especially challenging, which seriously debilitates their applications in sensor devices. Herein, for the first time, we presented a high fluorine content platinum porphyrin-grafted poly(isobutyl methacrylate-co-dodecafluoroheptyl methacrylate) copolymers (PtTFPP-p(IBM-co-DFHMA)) microfibrous thin-films used as optical oxygen sensors. The porous thin-film frameworks were formed of uniform microfibers, which afforded an exceptional improvement in sensitivity and exhibited 584% higher sensitivity than the solid sensing film owing to the large specific surface area, porous structures and oxygen diffusion enhancement by fluorine elements. Additionally, the remarkable emission intensity-changing characteristic of the microfiber sensing film under various air pressures facilitates convenient visualization of pressure distributions on film surface. The characteristics are particularly important for the computational fluid dynamics simulations in various sensing fields such as unsteady flow visualization and unsteady pressure measurements, etc. Owing to its attractive advantages and versatile performance, fluorine-containing copolymers fibers are expected to provide a new strategy for the rational design of high performance gas sensor devices.

Flexible electrode plays a key role in flexible energy storage devices. The SnTe/C nanofibers membrane (SnTe/CNFM) with excellent mechanical flexibility has been successfully synthesized for the first time through electrospinning, and it demonstrates outstanding electrochemical performance as free-standing anode for lithium/sodium-ion batteries. The SnTe/CNFM electrode delivers a discharge capacity of 526.7 mAh g−1 at 1000 mA g−1 after 1000 cycles in lithium-ion half-cells and a discharge capacity of 236.5 mAh g−1 at 500 mA g−1 after 80 cycles in lithium-ion full-cells with a LiFePO4 cathode. Not only that, it shows a discharge capacity of 182.7 mAh g−1 at 200 mA g−1 after 200 cycles in sodium-ion half-cells and a high discharge capacity of 207.0 mAh g−1 at 500 mA g−1 after 50 cycles in sodium-ion full-cells with a Na0.44MnO2 cathode. Moreover, the prepared SnTe/CNFM exhibits good mechanical flexibility. The SnTe/CNFM can still return to its original state without any breakage after bending, curling, folding and kneading. These results indicate that SnTe/CNFM is expected to become one of the promising free-standing anodes for lithium/sodium-ion batteries.

The excellent electrochemical performance of indium sulfide (In2S3) in lithium ion batteries (LIBs) and sodium ion batteries (SIBs) prompted us to explore its energy storage mechanism in potassium ion batteries (PIBs). In this work, In2S3/C nanofibers are successfully synthesized by simple electrospinning and subsequent vulcanization. In K half cells, compared to commercial In2S3 electrodes, In2S3/C nanofibers as anode materials for PIBs show outstanding electrochemical performance, which can deliver reversible capacities of 397.6 (25), 366.2 (50), 335.2 (100), 307.8 (200), 260.4 (500) and 212.2 mAh g−1 (1000 mA g−1), respectively. In K full cells, In2S3/C nanofibers can also show good potassium storage performance and can light up 15 light emitting diodes (LEDs). The superb electrochemical performance of In2S3/C nanofibers is due to the in-situ composite with self-nitrogen-doped carbon matrix and the nanoization of In2S3 particles, which buffers the volume effect and improves the conductivity of the material during the potassium storage process. In addition, the mechanism of potassium storage of In2S3/C nanofibers was systematically studied by cyclic voltammetry (CV), ex-situ XRD, TEM and XPS methods. The mechanism of In2S3 for K-ion storage can be described as the conversion reaction: In2S3 + 6K+ + 6e− ⇌ In + 3K2S.

Both antimony selenide and antimony are promising anode materials for lithium-ion batteries. However, owing to the influence of the poor electronic conductivity of Sb2Se3 and the large volume expansion of the two materials during the lithiation process, their electrochemical performance is limited and the practical application is restricted. In this work, for the first time, the hierarchical Sb2Se3 and Sb particles fully encapsulated into carbon nanofibers (Sb2Se3/Sb/C nanofibers) have been in-situ synthesized by electrospinning followed by controlled annealing. Combining the advantages of high specific capacity of Sb2Se3, good electronic conductivities of Sb and C, and strong stability of C matrix, the Sb2Se3/Sb/C nanofibers electrode shows excellent lithium-storage performance. It achieves a high reversible capacity (764 mA h g−1 after 300 cycles at 0.1 A g−1), splendid ultralong cycling stability (429 mA h g−1 after 1000 cycles at 1 A g−1), and high rate capability (342 mA h g−1 at 5 A g−1). It demonstrates that Sb2Se3/Sb/C nanofibers are promising high-performance anode materials for lithium-ion batteries.

The key to the development of wearable electronic equipment lies in the design of flexible batteries, in which the electrodes with outstanding mechanical behavior are quite important. Herein, porous nitrogen-doped Sn/C fibers (P-Sn/C-N Fs) film has been successfully synthesized via simple electrospinning and subsequent calcination process in which folic acid and polymethylmethacrylate (PMMA) play the role of introducing nitrogen and forming pores, respectively. The introduction of nitrogen improves the electronic conductivity of the material, and the presence of porous structure increases the specific surface area. More importantly, when the P-Sn/C-N Fs film is used directly as a free-standing electrode for lithium ion batteries, it exhibits outstanding electrochemical performance. The P-Sn/C-N Fs film exhibits a discharge capacity of 712.1 mAh g−1 at 500 mA g−1 after 500 cycles. Even at the high current density of 5 A g−1, it displays a high discharge capacity of 429.1 mAh g−1 after 1000 cycles. These findings indicate that the P-Sn/C-N Fs film has the potential to be applied as free-standing anode materials for lithium ion batteries.

New amphiphilic star or multi-arm block copolymers with different structures were synthesized for enabling the use of hydrophobic oxygen probe of platinum (II)-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) for bioanalysis. The amphiphilic star polymers were prepared through the Atom Transfer Radical Polymerization (ATRP) method by using hydrophilic 4-arm polyethylene glycol (4-arm-PEG) as an initiator. Among the five block copolymers, P1 series (P1a, P1b, and P1c) and P3 possess fluorine-containing moieties to improve the oxygen sensitivity with its excellent capacity to dissolve and carry oxygen. A polymer P2 without fluorine units was also synthesized for comparison. The structure-property relationship was investigated. Under nitrogen atmosphere, high quantum efficiency of PtTFPP in fluorine-containing micelles could reach to 22% and long lifetime could reach to 76 μs. One kind of representative PtTFPP-containing micelles was used to detect the respiration of Escherichia coli (E. coli) JM109 and macrophage cell J774A.1 by a high throughput plate reader. In vivo hypoxic imaging of tumor-bearing mice was also achieved successfully. This study demonstrated that using well-designed fluoropolymers to load PtTFPP could achieve high oxygen sensing properties, and long lifetime, showing the great capability for further in vivo sensing and imaging.

Phase transformation of TiO2 powder (P25) and pure anatase (PA) was investigated under pure oxygen as well as vacuum from 500 to 1,000 °C. The rutile percentage calculated based on the XRD data was used to estimate the phase transformation process. It was found that the vacuum suppressed the phase transformation of P25 relative to pure oxygen atmosphere. A model was proposed to explain the effect of oxygen on the phase transformation of TiO2. Furthermore, P25 samples showed lower phase transformation temperature (between 600 and 800 °C) compared with PA (over 1,000 °C). The existed rutile phase in P25 was regarded as a transformation inducer due to an interface between anatase and rutile phases since the nucleation activation energy on the interface is lower than that on the surface. And this interface effect is also adopted to explain the role of additive WO3, which retarded the phase transformation of P25 but promoted the phase transformation of PA.