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Optical manipulation of colloidal systems is of high interest for both fundamental studies and practical applications. It has been shown that optically induced thermophoresis and nonlinear interactions can significantly affect the properties of dense colloidal media. However, macroscopic scale phenomena can also be generated at thermal equilibrium. Here, we demonstrate that steady-state variations of particle density can be created over large, three-dimensional regions by appropriately structured external optical fields. We prove analytically and experimentally that an optical vortex beam can dynamically control the spatial density of microscopic particles along the direction of its propagation. We show that these artificial steady-states can be generated at will and can be maintained indefinitely, which can be beneficial for applications such as path clearing and mass transportation.

To replace precious Pt-based counter electrodes (CEs) with a low-cost Pt-free catalyst of CEs is still a motivating hotspot to decrease the fabrication cost of dye-sensitized solar cells (DSSCs). Herein, four different V2O3@C composite catalysts were synthesized by pyrolysis of a precursor under N2 flow at 1100 °C and further served as catalytic materials of CEs for the encapsulation of DSSCs. The precursors of V2O3@C composites have been prepared via a sol-gel method using different proportions of V2O5 with soluble starch in a H2O2 solution. Power conversion efficiencies (PCEs) of 3.59, 4.79, 5.15, and 5.06% were obtained from different V2O3@C composites, with soluble starch-to-V2O5 mass ratios (S/V) of 1:2, 1:1, 2:1, and 4:1, respectively, as CEs to reduce iodide/triiodide in DSSCs. The improvement of electrode performance is due to the combined effects on the increased specific surface area and the enhanced conductivity of V2O3@C composite catalysts.

Organic long-persistent luminescent materials can be easily quenched in aqueous solutions or air, which limits their wide applications. Here we report novel doped organic crystals to overcome this challenge. The stable LPL performance of this crystalline material is visible for over 8 s and can be maintained for at least three months even in aqueous solution or in air.

The traditional counter electrodes (CEs) catalysts are mainly noble Pt-based materials, but their scarcity and high cost impede their practical applications, especially in dye sensitized solar cells (DSSCs). Hence, identifying Pt-free catalyst materials for CEs have been regarded as one of the crucial steps to improve energy conversion efficiency and cost effectiveness of DSSCs. Herein, a feasible one-step reduction was put forward to prepare V2O3@C composites utilizing V2O5 as metal sources, and the soluble starch as carbon source. The four V2O3@C composite catalysts have successfully been prepared and further were applied to CEs as catalytic materials in the encapsulation of DSSCs. The power conversion efficiencies (PCE) of 2.79, 3.94, 5.13 and 4.97% were respectively obtained from mass ratios of the soluble starch to V2O5 with 1:2, 1:1, 2:1 and 4:1 as counter electrode for the regeneration of I3−/I− redox couples. The enhanced performance can be ascribed to the number of active catalytic sites and the distribution channels on the V2O3@C composites CEs, which was caused by that the larger surface area and higher conductivity of amorphous C from the pyrolyzed carbonization of the soluble starch in the precursor.

Oxygen deficient TiO2 has attracted extensive attention owning to its narrow bandgap and high electrical conductivity. In this work, novel yellow TiO2 with hierarchically porous architecture is fabricated by a facile pyrolysis method in air via a biomass template. The obtained yellow TiO2 exhibits interesting lithiation induced activation during cycling, which gives rise to a phase change from poorly crystallized TiO2 to an amorphous phase, accompanied by a colour change from yellow to black. In contrast to the intercalation mechanism reported in most of the literature on the TiO2 anode of LIBs, notably, the reversible redox reaction between Ti3+ and metal Ti can be verified in this case, demonstrating the novel conversion reaction mechanism of the TiO2 electrode. Based on this, the yellow porous TiO2 delivers enhanced electrochemical performance as an anode for LIBs with a superior capacity of 480 mA h g−1 at 5 A g−1 and a high capacity of 206 mA h g−1 at 10 A g−1 after 8000 cycles.

A naturally fibrous carbon foam is fabricated by employing fish bones as raw materials. Differing to carbon foams in previous reports, numerous unwoven and cross-linked carbon nanofibers were found to construct the whole foam, exhibiting a hierarchical porosity with interconnected channels and multisize pores. In the meantime, on the basis of the rich organic–inorganic components of fish bones, an N-S-P-O codoping was achieved in carbon foams. Benefiting from the synergistic effects of hierarchically porous fibrous foam and multiple heteroatom doping, the as-obtained samples were employed both as anode and cathode materials in lithium ion hybrid supercapacitors (LIHC), which delivered a superior energy density of 131 Wh kg–1 in 0–4.0 V. Significantly, at an impressive power density of 62000 W kg–1, the energy density of this device can still reach an ultrahigh energy density of 72 Wh kg–1, which presents a state of the art supercapacitors. More importantly, continuously being charged/discharged at a high ...

Synthesis of the electrode materials of sodium-ion storage devices from sustainable precursors via green methods is highly desirable. In this work, we fabricated a unique N, O dual-doped biocarbon nanosheet with hierarchical porosity by direct pyrolysis of low-cost cuttlebones and simple air oxidation activation (AOA) technique. With prolonging AOA time, thickness of the carbon sheets could be reduced controllably (from 35 to 5 nm), which may lead to tunable preparation of carbon nanosheets with a certain thickness. Besides, an unexpected increase in N-doping amount from 7.5 to 13.9 atom % was observed after AOA, demonstrating the unique role of AOA in tuning the doped heteroatoms of carbon matrix. This was also the first example of increasing N-doping content in carbons by treatment in air. More importantly, by optimizing the thickness of carbon sheets and heteroatom doping via AOA, superior sodium capacity-cycling retention-rate capability combinations were achieved. Specifically, a current state-of-the-art Na

Further development of multiphoton microscopic imaging is confronted with a number of limitations, including high-cost, high complexity and relatively low spatial resolution due to the long excitation wavelength. To overcome these problems, for the first time, we propose visible-to-visible four-photon ultrahigh resolution microscopic imaging by using a common cost-effective 730-nm laser diode to excite the prepared Nd(3+)-sensitized upconversion nanoparticles (Nd(3+)-UCNPs). An ordinary multiphoton scanning microscope system was built using a visible CW diode laser and the lateral imaging resolution as high as 161-nm was achieved via the four-photon upconversion process. The demonstrated large saturation excitation power for Nd(3+)-UCNPs would be more practical and facilitate the four-photon imaging in the application. A sample with fine structure was imaged to demonstrate the advantages of visible-to-visible four-photon ultrahigh resolution microscopic imaging with 730-nm diode laser excited nanocrystals. Combining the uniqueness of UCNPs, the proposed visible-to-visible four-photon imaging would be highly promising and attractive in the field of multiphoton imaging.

Simulated emission depletion (STED) microscopy is very powerful, but still suffers from small tissue penetration depth, photobleaching of fluorescent probes and complicated imaging systems. Here, we propose an optical luminescence depletion mechanism employing upconverting nanoparticles (UCNPs) and explore its potential for multi-photon STED-like microscopy. With the addition of Yb3+ ions in NaYF4:Er3+ UCNPs, the two-photon green emission of Er3+ under 795-nm excitation was successfully depleted by 1140-nm laser through the synergetic effect of the excited state absorption and the interionic energy transfer. This STED-like depletion mechanism was systematically investigated using steady-state rate equations, evidenced by the surprising emerging of 478-nm emission. The green emission depletion efficiency was about 30%, limited by the current laser source. Our work indicates that NaYF4:Yb3+/Er3+ UCNPs will be potential probes for multi-photon super-resolution microscopy with many advantages, including long-wavelength-induced large penetration, non-photobleaching and non-photoblinking properties, cost-effective and simplified imaging systems.

Simultaneous deep macroscopic imaging and microscopic imaging is in urgent demand, but is challenging to achieve experimentally due to the lack of proper fluorescent probes. Herein, we have designed and successfully synthesized simplex Er(3+)-doped upconversion nanoparticles (UCNPs) with double excitation bands for simultaneous deep macroscopic and microscopic imaging. The material structure and the excitation wavelength of Er(3+)-singly doped UCNPs were further optimized to enhance the upconversion emission efficiency. After optimization, we found that NaYF4:30%Er(3+)@NaYF4:2%Er(3+) could simultaneously achieve efficient two-photon excitation (2PE) macroscopic tissue imaging and three-photon excitation (3PE) deep microscopic when excited by 808 nm continuous wave (CW) and 1480 nm CW lasers, respectively. In vitro cell imaging and in vivo imaging have also been implemented to demonstrate the feasibility and potential of the proposed simplex Er(3+)-doped UCNPs as bioprobe.

Nanosized monodispersed spherical titania particles with the anatase structure have been synthesized by forced hydrolysis of titanium sulfate at boiling reflux. The products were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM).

Upconversion nanoparticles (UCNPs) is a class of promising probes widely used in protein molecules imaging due to the no photobleaching and non-blinking emission. However, it is still remained challenging to synthesize a type of ultra-small but bright UCNPs. In this paper, a new class of efficient sub-5-nm upconversion nanodots (UCNDs) was elaborately designed and experimentally demonstrated. The proposed uniform UCNDs comprise two parts: a 3.5-nm Ln3+-doped ZrO2 core and 0.5-nm NaYF4 shell. The emission intensity of the proposed UCNDs was measured to be more than 10 times brighter than that of the conventional 10-nm NaYF4 UCNPs. Under 300 kW·cm−2 irradiance excitation, the 15 mol% Er3+-doped UCNDs exhibit an 18-fold enhanced intensity and one fifth emission lifetime compared to the 0.5 mol% Er3+-doped ones. Using the biocompatible UCNDs, the aptamer-mediated proteins-targeted imaging was performed and demonstrated high efficiency. These ultra-small, efficient UCNDs would have great potentials in rapid scanning and cellular imaging.