Herein, we develop a novel sensitive fluorescent probe with an open core/shell nanostructure (OCSNS), rod-Y2O3:Eu3+@0.01YVO4:Eu3+, in which a YVO4:Eu3+ shell with a thickness of less than 5 nm partially covers an anisotropic core of rod-Y2O3:Eu3+. The photo-luminescent performance of the OCSNS is sensitive to trace ions or molecules. High-resolution transmission electron microscopy (HR-TEM) observations clearly confirm that this OCSNS has an open quantum shell of YVO4:Eu3+. In contrast to closed core Y2O3:Eu3+@shell YVO4:Eu3+, which has only one excitation band peaking at ∼308 nm, this novel nanostructure has a wide-wavelength excitation response that can be decomposed into two components centered at ∼254 and ∼280 nm, which stem from open core rod-Y2O3:Eu3+ and the YVO4:Eu3+ quantum shell, respectively. As expected, this OCSNS shows “off-and-on” fluorescence properties due to the strong surface effect of this open quantum shell: it is “off” when detecting trace Cu(II) ions and “on” when detecting trace amino acids, at levels as low as 10−8 mol L−1. Hence, rod-Y2O3:Eu3+@0.01YVO4:Eu3+ could be an excellent candidate for sensitive fluorescent probes, showing similar performance to most quantum dots for the detection of ions and molecules. Moreover, it is both easier to fabricate and more stable than quantum dots.

Data storage with ultrahigh density, ultralow energy, high security, and long lifetime is highly desirable in the 21st century and optical data storage is considered as the most promising way to meet the challenge of storing big data. Plasmonic coupling in regularly arranged metallic nanoparticles has demonstrated its superior properties in various applications due to the generation of hot spots. Here, the discovery of the polarization and spectrum sensitivity of random hot spots generated in a volume gold nanorod assembly is reported. It is demonstrated that the two-photon-induced absorption and two-photon-induced luminescence of the gold nanorods adjacent to such hot spots are enhanced significantly because of plasmonic coupling. The polarization, wavelength, and spatial multiplexing of the hot spots can be realized by using an ultralow energy of only a few picojoule per pulse, which is two orders of magnitude lower than the value in the state-of-the-art technology that utilizes isolated gold nanorods. The ultralow recording energy reduces the cross-talk between different recording channels and makes it possible to realize rewriting function, improving significantly both the quality and capacity of optical data storage. It is anticipated that the demonstrated technology can facilitate the development of multidimensional optical data storage for a greener future.

We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2–SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into “coffee” rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly revealed in the anti-Stokes hyper-Raman scattering. Apart from the strong anti-Stokes hyper-Raman scattering, Stokes hyper-Raman scattering with small Raman shifts was detected during the ablation process of thick MoS2 layers. It was also observed by slightly defocusing the excitation light. The detection of anti-Stokes hyper-Raman scattering may serve as a new technique for studying the Raman inactive vibration modes in nanomaterials.

•The upconversion luminescence of Eu3+ ion in calcium aluminoborate glass was demonstrated.•β-NaYF4 crystal was melted into aluminoborate matrix to form a homogeneous vitreous material.•The existences of β-NaYF4 and Bi3+ ion can enhance the upconversion luminescence of Eu3+.•The UC emission of Eu3+ in glass matrix can be induced by two-photon simultaneous absorption.The upconversion luminescence (UCL) of Eu3+ ion in calcium aluminoborate glass matrix with the composition of CaO–Al2O3–B2O3 (CaAlB) under 800 nm laser excitation has been demonstrated and the structural, thermal and optical properties of Eu3+-doped glasses were investigated by X-ray diffractometry (XRD), Fourier transform infrared (FT-IR), thermogravimetry-differential scanning calorimetry (TG-DSC) and photoluminescence (PL) analyses. The results revealed that these glasses possess good thermal, chemical and mechanical stabilities. For improving the UCL of Eu3+, β-NaYF4 crystal was successfully melted into CaAlB matrix to form a homogeneous vitreous material (CaAlB/NaYF4). The result indicated that the UC emission of Eu3+ in CaAlB/NaYF4 composite matrix observably increases due to reduced phonon energy of CaAlB matrix and high UC quantum efficiency of NaYF4 matrix. Similarly, additive Bi3+ ion can improve the UC emission of Eu3+ ion via reducing the phonon energy of the host. The UC emission of Eu3+ in CaAlB/NaYF4 composite matrix can be induced by two-photon simultaneous absorption. The results imply that these investigated glasses may be potential candidates for UCL and fiber materials.

The electrochemical behaviors and simultaneous determination of three dihydroxybenzene isomers, i.e., catechol (CC), resorcinol (RC), and hydroquinone (HQ), are studied using a thermally reduced carbon nano-fragment modified glassy carbon electrode (CNF/GCE). The soluble CNF modifier with unique micro-/nano-structure and abundant edges and defective sites is prepared by chemically oxidizing graphite powders, ultrasonically crushing, and thermally reducing treatment in turn. It is shown that the oxidation peak currents of CC, RC, and HQ at the CNF/GCE are improved about 1.74, 2.88, and 1.05 times compared to that of the GCE. The diffusion process in bulk solution controls the electrochemical reaction of CC, RC, and HQ, and their reversible electrochemical process involves equal numbers of protons and electrons. Based on the enhanced electrocatalytic activity and enlarged separation of the anodic peak potential towards three dihydroxybenzene isomers at the CNF/GCE, the simultaneous differential pulse voltammetry (DPV) determination of CC, RC, and HQ, with detection limits (S/N = 3) of 5.0 × 10−7 mol L−1, 8.0 × 10−7 mol L−1 and 4.0 × 10−7 mol L−1, respectively, are obtained. The CNF/GCE also indicates high selectivity, stability, and reproducibility, and is comparable with results of high-performance liquid chromatography in real samples, clearly indicating its applicability.

The linear and nonlinear optical properties of thin MoS2 layers exfoliated on an Au/SiO2 substrate were investigated both numerically and experimentally. It was found that the MoS2 layers with different thicknesses exhibited different colors on the gold film. The reflection spectra of the MoS2 layers with different thicknesses were calculated by using the finite-difference time-domain technique and the corresponding chromaticity coordinates were derived. The electric field enhancement factors at both the fundamental light and the second harmonic were calculated and the enhancement factors for second harmonic generation (SHG) were estimated for the MoS2 layers with different thicknesses. Different from the MoS2 layers on a SiO2/Si substrate where the maximum SHG was observed in the single-layer MoS2, the maximum SHG was achieved in the 17 nm-thick MoS2 layer on the Au/SiO2 substrate. As compared with the MoS2 layers on the SiO2/Si substrate, a significant enhancement in SHG was found for the MoS2 layers on the Au/SiO2 substrate due to the strong localization of the electric field. More interestingly, it was demonstrated experimentally that optical data storage can be realized by modifying the SHG intensity of a MoS2 layer through thinning its thickness.

The tin dioxide (SnO2) nanocrystals were synthesized by direct precipitation method and a series of SnO2 samples were obtained via calcining SnO2 at different temperatures. The characteristics of SnO2 samples were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), Brunauer Emmett Teller (BET), photoluminescence spectroscopy (PL), and UV–vis diffuse reflectance spectroscopy (DRS). The effects of calcination temperatures and additives on the photodegradation of methylene blue (MB) on SnO2 samples under UV-light irradiation have been researched. The results showed that the SnO2 sample with low temperature-treated (T≤200 °C) exhibits the highest degradation efficiency, while with increasing temperature-treated (from 400 °C to 1000 °C) SnO2 samples show decreasing degradation activities. The additives, such as methanol, sodium fluoride, Fe(III), Ag+, and terephthalic acid showed different influences on MB degradation in UV/SnO2 systems. It has been demonstrated that in SnO2-MB systems both hydroxy radicals (OH) generated on the surface of SnO2 and photogenerated holes (h+vb) in the valence band (VB) of SnO2 jointly control the photo-oxidation process of MB. In SnO2 system with increasing temperature-treated (T≥400 °C) the contribution of OH to MB degradation gradually decreased due to the diminution of surface-bonding hydroxyl groups (–OH) and chemisorbed water (H2O) molecules on the surface of SnO2, by comparison, the contribution of h+vb increased. The effects of Ag+ and Fe(III) species on MB degradation and the formation of OH were investigated in detail and the mechanisms have been discussed. The presence of Ag+ ion at low concentration promotes the degradation of MB by capturing the photogenerated electrons (ecb−) on the surface of SnO2 catalyst, suppressing the recombination of photogenerated electrons and holes. The presence of Ag+ ion at high concentration observably reduces the degradation in catalyst system which the photodegradation process is controlled by OH, conversely, it intensively promotes the degradation in which the photodegradation process is controlled by h+vb. The effects of Fe(III) species on the degradation are similar to those of Ag+ ions.

The new calcium aluminoborate glasses with the composition of CaO–Al2O3–B2O3–RE2O3 (RE = Dy and Tb) were synthesized and the luminescence of Dy3+ and Tb3+ was investigated. The results show that the emission intensity of Tb3+ ion was enhanced when introducing Dy3+ ion into CaO–Al2O3–B2O3–Tb2O3 glass due to the energy transfer processes between Dy3+ and Tb3+. The energy transfer efficiencies, transfer probabilities as well as donor–acceptor critical distances were also calculated. The energy transfer mechanism between Dy3+ and Tb3+ ions is electric dipole–dipole interaction, which can be concluded by both fluorescence decay and emission intensity ratio varieties.Highlights► A new Dy3+/Tb3+ co-doped calcium aluminoborate glass was fabricated. ► The luminescence properties of this glass were investigated. ► The energy transfer process of Dy3+ → Tb3+ was confirmed. ► The electric dipole–dipole interactions are responsible for the energy transfer.

Well-dispersed superparamagnetic nanocomposites, mesoporous silica-coated nano-sized magnetite (MSNSM) as a magnetic carrier and CuO-coated MSNSM (CuO-MSNSM) as a new desulfurizer have been reported. The MSNSM, prepared via a nano-assembling method by using cationic surfactants as templates, consists of a 12-nm-in-diameter core of magnetite particle and about 4-nm-thickness shell of mesoporous silica (MS), and shows high specific surface area (ca. 154 m2/g). The CuO-MSNSM was obtained by immersing the MSNSM into a copper solution, which formed a nano-scaled particle of CuO onto the surface of MSNSM upon followed calcination. The results revealed that both MSNSM and CuO-MSNSM exhibit strongly superparamagnetic properties with saturation magnetization values (Ms) of over 28 emu/g. Both would be potential functional magnetic carriers. As an example of its wide applications, the CuO-MSNSM was tested as a desulfurizer. It was found that the CuO-MSNSM is an excellent organic sulfur adsorber, performing fully separation of the organic sulfur in a model dodecanethiol-added petroleum liquid.

A series of amino acid-coated nano-sized magnetite (AA-NSM) particles such as leucine (Leu), arginine (Arg), cysteine (Cys), cystine, aspartate (Asp) and tyrosine (Tyr), were synthesized by a two-step transformation (TST) process. The TST process consists of the following steps: firstly preparing oxalate modified NSM (Ox-NSM) at pH 9 and secondly substituting AA for Ox to form AA-NSM at pH 5. Both the Ox- and AA-NSM particles were clearly confirmed by the FT-IR spectra and TGA curves. The content of each AA in the AA-NSM appeared different because of the difference in both the structure and isoelectric point of each AA molecule. It is noteworthy that Ox, as a template in the intermediate Ox-NSM, plays a key role in the formation of AA-NSM with free NH2 group inside. All of the AA-NSMs showed superparamagnetic property without hysteresis at room temperature and had strong saturated magnetization value (more than 50 emu/g), which may have potential applications in both biomedical and environmental areas.