Enhancing hologram memory via deposition of plasmonic nanocubes on orderly mesoporous titania.

Hologram is regarded as a key platform for large-volume data storage and information encryption. Diversity of plasmonic nanostructures makes it being a kind of vibrant hologram memory media. However, recording of amplitude, phase and polarization of light is restricted by difficulty to obtain anisotropic morphology of metal particles. Photocatalysis approach allows wide size distribution of Ag plasmonic nanoparticles after a long growth time on titania but suffers from the disadvantage that the shape of plasmonic nanostructures is mostly isotropic, which weakens optical vector sensitivity and information stability. Herein, Ag nanocubes exhibiting high polarization response ability are deposited on orderly mesoporous titania via UV photocatalysis. Recording efficiency of hologram by orthogonally linearly polarized lights is enhanced and the memorized information can be resistant to UV-erasure, both benefiting from the distal resonance of Ag nanocubes. This work delivers a guideline for long-term data storage and high-efficiency display devices.

Graphene-oxide/TiO2 nanocomposite films with electron-donors for multicolor holography.

Graphene oxide (GO) with an ideal two-dimensional structure, presents outstanding optical, electric, and mechanical properties which draws great attention in advanced information devices. Recently, GO-based films were found to show photochromic behavior, especially for the TiO2 involved system which has potential data processing capability, such as storing holograms. However, expanding spectral response range and increasing exposure sensitivity are still challenges for such a film, due to the limited photo-quantum efficiency in reduction reaction. Here, an innovative method of "Immersion-Dropping" technology is proposed to fabricate GO-based continuous films. We, for the first time, achieve colored holography from violet to yellow regions on GO/TiO2 nanocomposite films with introduction of weak acid molecules. A "diffraction self-enhancement" is observed. The obtained results benefit from the broadband photo-response of weak acid molecules and photo-triggered transferring of electrons in multi-channels. This work provides a research strategy for the large-capacity information storage and colorful display device.

Bi-photonic reduction of anisotropic Ag nanoparticles for color-tunable hologram reconstruction.

Efficient optical phase modulation is essential for information processing. The polarization response of metallic nanoparticles plays a key role in the formation of vector hologram. Commonly, Ag nanoparticles reduced by incoherent UV lamp tend to grow in isotropy, which is unsuitable for the formation of polarization hologram and the resultant multicolor holograms recording-readout in polarization channels. Here, the Ag nanoparticles storage with high polarization-sensitivity and anti-radiation interference are realized via bi-photonic irradiation from UV and visible lasers with participation of electron-acceptor. For the first time, the orthogonal polarization storage efficiency of the system is higher than that of the parallel mode. Color-tunable holographic reconstruction by polarization-multiplexing is achieved. This work provides a significant research strategy for stable, high-density data storage and advanced display.

Visible laser-assisted reduction of plasmonic Ag nanoparticles with narrow-band optical absorption for colored holographic reconstruction.

Noble metal plasmonic resonance has been utilized in optical data storage widely for its excellent photo-transformation efficiency. TiO2 nanoporous films deposited with Ag nanoparticles present outstanding polarization-response and color-modulation ability. However, the low exposure-sensitivity at single wavelength inhibits their application in optical information processing, which is urgent to be improved by innovative methods. Here, we report that Ag nanoparticles were deposited efficiently via continuous laser irradiation in the TiO2 nanoporous film treated by tannic acid, presenting high-efficient monochromic absorption property. As a result, two sets of holograms were recorded sequentially at the same point of the film with orthogonal circular polarization configurations. The colored reconstruction of the mixed holograms was achieved by utilizing laser polarization state as chrominance segmentation channel. Our method provides a distinctive route for enhancing the photo-energy conversion efficiency of plasmonic nanoparticles, and paves a way to develop advanced display device.

Nonvolatile plasmonic holographic memory based on photo-driven ion migration.

Stability of data storage is essential for optical information processing. TiO2 nanoporous films loaded with small-sized Ag nanoparticles thus attracted much attention due to their fast and polarization-sensitive photochemical response, which is able to realize optical phase modulation and high-density optical memory. However, little attention was given to the modulation of the silver ion migration, which plays a key role in anti-erasure of the recorded hologram. In this paper, the strong coupling of two phase gratings was achieved by long-term recording in the Ag-TiO2 film irradiated with a pair of coherent left- and right-hand circular polarization lights from a Blu-ray (∼405 nm) laser. The migration of Ag+ ions was enhanced by the electronic field gradient force. A stable polarization holographic grating was obtained by this method and observed by a polarizing microscope. This work provided a strategy for a nonvolatile device based on photo-driven ion migration.

Selective photo-oxidation induced bi-periodic plasmonic structures for high-density data storage.

Stable and controllable optical memory is necessary for the development of current information technology. In this context, Ag/TiO2 films have received much attention for their photosensitivity in wavelength and polarization, which can be applied to high-density optical storage. Here, we carried out dual-wavelength holographic recording using 403.4 nm and 532 nm lasers, and obtained mixed microfringes based on selective photodissolution of Ag nanoparticles of various sizes in TiO2 nanoporous films. Two recording methods of simultaneous and sequential multiplexing were investigated. It was found that using simultaneous irradiation it is easier to obtain equivalent efficiency in both spectral hole burning and multiplexed grating diffraction, compared with the sequential one. The results can be explained by the Time-accumulation effect during Ag+ ion diffusion and migration in holographic recordings. Based on such properties, multiplexed-holographic fringes with uniform contrast were reserved by simultaneous recording in Ag/TiO2 films. This work provides a new strategy for fabrication of photonic devices with complex microstructures.

Selective detection of carbendazim using a upconversion fluorescence sensor modified by biomimetic molecularly imprinted polymers.

The persistence of carbendazim residues in the food chain poses a potential risk to human health. Therefore, an eco-friendly selective and sensitive fluorescence nanosensor was established for carbendazim determination based on molecularly imprinted polymer (MIP) modified upconversion nanoparticles (UCNPs). The molecularly imprinted coating with methacrylamide as a functional monomer and carbendazim as a template molecule grafted on the UCNPs (UCNPs@MIP) constituted fluorescent recognition elements. The fluorescence emission of UCNPs@MIP significantly declined in the presence of carbendazim due to electron transfer induced by its selective binding with MIP cavities. The quenched fluorescence of UCNPs@MIP was recovered once the template carbendazim was eluted from the probe system. Under the optimized conditions, the proposed method offers a good linear correlation between 0.01 and 1 µg/mL, with a limit of detection (LOD) of 0.0036 µg/mL for carbendazim residues. The analytical utility and reliability of the developed biomimetic platform were examined in real food samples with good recoveries (88.790%∼102.675%) and relative standard deviation (RSD) values (0.491%∼3.779%). The method was further validated by a standard HPLC method in terms of student's t-test (p > 0.05) with no significant differences between the two methods. Hence, the proposed fluorescence sensor has prospects for rapid determination of carbendazim.

Plasmonic Optoelectronic Memristor Enabling Fully Light-Modulated Synaptic Plasticity for Neuromorphic Vision.

Exploration of optoelectronic memristors with the capability to combine sensing and processing functions is required to promote development of efficient neuromorphic vision. In this work, the authors develop a plasmonic optoelectronic memristor that relies on the effects of localized surface plasmon resonance (LSPR) and optical excitation in an Ag-TiO2 nanocomposite film. Fully light-induced synaptic plasticity (e.g., potentiation and depression) under visible and ultraviolet light stimulations is demonstrated, which enables the functional combination of visual sensing and low-level image pre-processing (including contrast enhancement and noise reduction) in a single device. Furthermore, the light-gated and electrically-driven synaptic plasticity can be performed in the same device, in which the spike-timing-dependent plasticity (STDP) learning functions can be reversibly modulated by visible and ultraviolet light illuminations. Thereby, the high-level image processing function, i.e., image recognition, can also be performed in this memristor, whose recognition rate and accuracy are obviously enhanced as a result of image pre-processing and light-gated STDP enhancement. Experimental analysis shows that the memristive switching mechanism under optical stimulation can be attributed to the oxidation/reduction of Ag nanoparticles due to the effects of LSPR and optical excitation. The authors' work proposes a new type of plasmonic optoelectronic memristor with fully light-modulated capability that may promote the future development of efficient neuromorphic vision.

Chitosan oligosaccharides promote reverse cholesterol transport and expression of scavenger receptor BI and CYP7A1 in mice.

Chitosan oligosaccharides (COS) are beneficial in improving plasma lipids and diminishing atherosclerotic risks. In this study, we examined the effects of COS on reverse cholesterol transport (RCT) in C57BL/6 mice. (3)H-cholesterol-laden macrophages were injected intraperitoneally into mice fed with various dosage of COS (250, 500, 1000 mg/kg mouse weight, respectively) or vehicle by gastric gavages. Plasma lipid level was determined and (3)H-cholesterol was traced in plasma, liver, bile and feces. The effects of COS on hepatic cholesterol 7 alpha-hydroxylase (CYP7A1) and scavenger receptor BI (SR-BI) expression were also investigated. COS administration led to a significant decrease in plasma total cholesterol and low-density lipoprotein (LDL) cholesterol and a significant increase in peritoneal macrophage-derived (3)H-cholesterol in liver and bile as well as in feces. Liver protein expressions of CYP7A1, SR-BI and LDL receptor (LDL-R) were improved in a dosage-dependent manner in COS-administered mice. Our findings provide the first in vivo demonstration of a positive role for COS in RCT pathway and hepatic CYP7A1 and SR-BI expression in mice. Additionally, the LDL cholesterol lowering effect might be relative to hepatic LDL-R expression stimulated by COS in mice.

Hydrogen decreases athero-susceptibility in apolipoprotein B-containing lipoproteins and aorta of apolipoprotein E knockout mice.

OBJECTIVE: It is to characterize the underlying molecular mechanisms of the anti-atherosclerotic effects of hydrogen (dihydrogen; H(2)), a novel antioxidant. In particular, to examine the effects of hydrogen on athero-susceptibility in lipoproteins and aorta of apolipoprotein E knockout (apoE-/-) mice. METHODS AND RESULTS: Plasma analysis by enzymatic method and spectrophotometric measurement showed that eight weeks intraperitoneally injection of hydrogen-saturated saline remarkably decreased plasma total and non-high-density lipoprotein (non-HDL) cholesterol, and malondialdehyde in apoE-/- mice fed either chow or high fat diet. Western blot analysis showed hydrogen treatment reduced the contents of apolipoprotein B (apoB), a major protein constituent of non-HDL in either plasma or hepatic tissues. Moreover, ELISA assay revealed that the production of tumor necrosis factor-α and interleukin-6 were significantly suppressed by hydrogen in RAW264.7 macrophages, after stimulation with the isolated non-HDL from treated or untreated mice. Immunohistochemistry of aortic valve sections revealed that hydrogen suppressed the expression of several proinflammatory factors and decreased vessel wall infiltration of macrophages. Besides, real-time PCR and Western blot analysis disclosed that hepatic scavenger receptor class B type I (SR-BI), ATP-binding cassette (ABC) transporters ABCG8, ABCB4, ABCB11, and macrophage SR-BI, were all induced by hydrogen treatment. Finally arterial wall lipid disposition displayed by oil red O staining was reduced significantly in aortic root and whole aorta en face in hydrogen administrated mice. In addition, hydrogen significantly improved HDL functionality in C57BL/6J mice assessed in two independent ways, namely (i) stimulation of cholesterol efflux from macrophage foam cells by measuring HDL-induced [(3)H]cholesterol efflux, and (ii) protection against LDL oxidation as a measure of Cu(2+)-induced TBARS formation. CONCLUSION: These results reveal that administration of hydrogen-saturated saline decreases athero-susceptibility in apoB-containing lipoprotein and aortic atherosclerosis in apoE-/- mice and improves HDL functionality in C57BL/6J mice.