Ruilin Zheng

Super-elastic graphene/carbon nanotube aerogels and their application as a strain-gauge sensor

A synergistic assembly strategy was developed to fabricate super-elastic all-carbon aerogels by integrating carbon nanotubes (CNTs) into three-dimensional graphene. The CNTs in the aerogels prevented the sliding between the graphene sheets and enhanced the stiffness of cell walls, which provided the aerogels with super-elasticity. Mechanical tests showed that the graphene/CNT aerogels could fully recover without fracture even after 90% compression. The potential application of the sensing compressive strain for the aerogels was also demonstrated. The electrical resistance response of the aerogels was highly constant to the multiple cycles of compression. The strain-gauge sensitivity of graphene/CNT aerogels could be tuned to considerably different values by controlling the aerogel density. Upon applying a strain of 30% and 60% to the graphene/CNT aerogel with a density of 37.8 mg cm−3, its strain-gauge sensitivities (gauge factor) reached 230% and 125%, respectively, which were superior to most of carbon-based compressible conductors.

Fabrication and characterization of carbon/oxygen-implanted waveguides in Nd3+-doped phosphate glasses

Abstract. Optical planar waveguides in Nd3+-doped phosphate glasses are fabricated by a 6.0-MeV carbon ion implantation with a dose of 6.0×1014 ions/cm2 and a 6.0-MeV oxygen ion implantation at a fluence of 6.0×1014 ions/cm2, respectively. The guided modes and the corresponding effective refractive indices were measured by a modal 2010 prism coupler. The refractive index profiles of the waveguides were analyzed based on the stopping and range of ions in matter and the RCM reflectivity calculation method. The near-field light intensity distributions were measured and simulated by an end-face coupling method and a finite-difference beam propagation method, respectively. The comparison of optical properties between the carbon-implanted waveguide and the oxygen-implanted waveguide was carried out. The microluminescence and Raman spectroscopy investigations reveal that fluorescent properties of Nd3+ ions and glass microstructure are well preserved in the waveguide region, which suggests that the carbon/oxygen-implanted waveguide is a good candidate for integrated photonic devices.

A fluorophosphate glass–ceramic electrolyte with superior ionic conductivity and stability for Na-ion batteries

All solid-state sodium-ion electrolytes have attracted increasing attention due to their wide range of applications in secondary batteries. Here, a new fluorophosphate glass–ceramic electrolyte, (Na2O + NaF)–TiO2–B2O3–P2O5–ZrF4 (NTBPZ), has been proposed and synthesized. Due to a low activation energy of 13.9 kJ mol−1 and reduced resistance at the grain boundaries, the NTBPZ glass ceramic has a room-temperature ionic conductivity as high as 3 × 10−5 S cm−1. In addition, the NTBPZ electrolyte has excellent thermal and chemical stabilities under ambient conditions. These outstanding performances make the NTBPZ a promising electrolyte for all-solid-state sodium-ion batteries.

Optimization effect of annealing treatment on oxygen-implanted Nd:CNGG waveguides

Neodymium-doped calcium niobium gallium garnet (Nd:CNGG) waveguide operated at 632.8 nm is demonstrated by the 3.0-MeV oxygen-ion implantation with a fluence of 6.0 × 1014 ions/cm2. The annealing treatment at 300∘C for 45 min is carried out to optimize the waveguide quality. The dark-mode spectra are measured by the m-line technique. The refractive index profiles are calculated from the effective refractive indices of the waveguide modes. The near-field intensity distributions are simulated based on the reconstructed refractive index profiles. The annealing treatment process could effectively remove unwanted defects and optimize the waveguide quality. The optical properties of the annealed waveguide are better than that of the as-implanted waveguide.

Flux-solvothermal preparation of dispersible LiLa0.4Nd0.6(PO3)4 microcrystals with regular morphology and superior fluorescence

A flux-solvothermal method was used to grow a type of novel dispersible LiLa0.4Nd0.6(PO3)4 microcrystals with high Nd3+ ions concentration of 2.63 × 1021 cm−3 and excellent fluorescence properties for the first time. By optimizing experimental conditions, microcrystals with sizes in the region of 1.5–5 μm, a strong emission intensity and long lifetime of 107 μs were obtained. The results show that their transparent dispersion in the mixed solvents of DMSO and CHBr2CHBr2 had a strong absorption at 800 nm, low solvent quenching ratio of 6.5%, high quantum yield of 32.17% and large emission cross section of 4.39 × 10−20 cm2 when the Nd3+ ions concentration is 1 × 1020 cm−3, which imply the microcrystals are of potential application in transparent glass-ceramics, dispersion amplifiers and lasers.

Planar waveguides in Yb3+-doped tellurite glasses fabricated by ion implantation of oxygen

A planar waveguide is demonstrated in the Yb3+-doped tellurite glass, using (5+6) MeV O3+ ion implantation with doses of (4+8)×1014 ions/cm2. The implantation process of O3+ ions into the Yb3+-doped tellurite glass is simulated by the stopping and range of ions in matter (SRIM) 2010 code. The dark-mode spectra are measured by the prism-coupling system at λ = 632.8 nm. The reflectivity calculation method and the finite-difference beam propagation method are used to calculate the refractive index profile and the modal profile of transverse electric (TE) mode of the fabricated waveguide, respectively. The absorption spectra show that the transmission properties are not affected by the waveguide fabrication process.

Optical waveguides fabricated by nitrogen ion implantation in fused silica

Abstract. We report on the fabrication of waveguides in fused silica using 4.5-MeV nitrogen ion implantation with a fluence of 5.0×1014  ions/cm2. The prism-coupling method was employed to measure the effective refractive indices of guiding modes at the wavelengths of 632.8 and 1539 nm. The effective refractive indices of the first few modes were higher than that of the substrate. The refractive index profiles at 632.8 and 1539 nm were reconstructed by the reflectivity calculation method. Positive index changes were induced in the waveguide layers. The end-face coupling method was used to measure the near-field light intensity distributions at the wavelength of 632.8 nm and the finite-difference beam propagation method was applied to simulate the guided mode profile at the wavelength of 1539 nm. The waveguide structures emerge as candidates for integrated photonic devices.

Active waveguides by low-fluence carbon implantation in Nd3+-doped fluorophosphate glasses

A planar waveguide in the Nd3+-doped fluorophosphate glass is fabricated by a 6.0 MeV C3+ ion implantation at a low-fluence of 1.0 × 1014 ions/cm2. The fluence is close to that in semiconductor industry. The dark mode spectra are recorded by a model 2010 prism coupler. The energy losses during the implantation process and the refractive index profile of the waveguide are simulated by the SRIM 2010 code and the reflectivity calculation method (RCM), respectively. The near-field light intensity profile and the propagation loss of the waveguide are measured by an end-face coupling system. The two-dimensional (2D) modal profile of transverse electric (TE) mode for the fabricated waveguide is calculated by the finite difference beam propagation method (FD-BPM). The results of microluminescence and optical absorption reveal that the spectroscopic characteristics of the Nd3+-doped fluorophosphate glass are nearly unaffected by the carbon ion implantation process. This work suggests that the carbon-implanted Nd3+-doped fluorophosphate glass waveguide is a promising candidate for integrated active devices.

Planar waveguides in neodymium-doped calcium niobium gallium garnet crystals produced by proton implantation

In this work, the fabrication and optical properties of a planar waveguide in a neodymium-doped calcium niobium gallium garnet (Nd:CNGG) crystal are reported. The waveguide is produced by proton (H+) implantation at 480 keV and a fluence of 1.0 x 10(17) ions/cm(2). The prism-coupling measurement is performed to obtain the dark mode of the waveguide at a wavelength of 632.8 nm. The reflectivity calculation method (RCM) is used to reconstruct the refractive index profile. The finite- difference beam propagation method (FD-BPM) is employed to calculate the guided mode profile of the waveguide. The stopping and range of ions in matter 2010 (SRIM 2010) code is used to simulate the damage profile induced by the ion implantation. The experimental and theoretical results indicate that the waveguide can confine the light propagation.

Insight into Chirality on Molecular Stacking for Tunable Ultralong Organic Phosphorescence

A new levorotatory compound ((S)-9,9′-(6-(1-phenylethoxy)-1,3,5-triazine-2,4-diyl)bis(9H-carbazole)) and its corresponding racemic compound show different intermolecular interactions to restrain nonradiative transition, resulting in an enhanced ultralong organic phosphorescence lifetime from 229.0 ms to 419.8 ms. This work will provide a new insight into the chirality of organic molecules to adjust the ultralong phosphorescence.