Bragg gratings with novel waveguide models fabricated in bulk glass via fs-laser writing and their slow-light effects.

We present the experimental realization of an innovative parallel partially overlapping waveguides (PO-WGs) model grounded in the thermal accumulated regime and fabricated using femtosecond (fs) laser direct-writing within low-iron bulk glass. The 75mm long novel PO-WGs model was made by partially overlapping the shell parts of two core-shell types of waveguides via a back-and-forth single pass fs-laser inscription. The detailed evolution of the PO-WGs model from inception to completion was offered, accompanying by a thorough characterization, which unveils a substantial refractive index (RI) change, on the order of 10-3, alongside low propagation loss (0.2 dB/cm) and distinctive features associated with the single mode and shell-guided light. Notably, the unsaturated performance of PO-WGs model after the primary inscription paves the way for potential applications in the successful creation of two distinctive types of Bragg gratings: first-order dot-Bragg grating and second-order line-Bragg grating. The 75 mm long dot-Bragg grating was written by a periodic dot array with a height of 6 µm atop the PO-WGs, and the birefringence was measured of 1.5 × 10-5 with a 16 pm birefringence-induced wavelength difference. The line-Bragg grating, which was inscribed with dual PO-WGs extending the line grating part to 40 mm in length along its period for increasing the transmission dip, exhibits a pronounced polarization dependence showcasing an effective birefringence of 4.2 × 10-4 at the birefringence-induced wavelength difference of 0.45 nm. We delved into the slow-light effects of the two Bragg gratings thoroughly, which the theoretical analysis revealed an effective group delay of 0.58 ns (group index 2.3) for the dot-Bragg grating. Similarly, the line-Bragg grating exhibited an effective group delay of 0.3 ns (group index 2.3), in good agreement with experimental measurements. These findings underscore the exciting potential of our gratings for creating optical slow-wave structures, particularly for future on-chip applications.

Fabrication of Fe3O4@SiO2@TiO2 nanoparticles supported by graphene oxide sheets for the repeated adsorption and photocatalytic degradation of rhodamine B under UV irradiation.

A quaternary nanocomposite Fe3O4@SiO2@TiO2/graphene oxide (GO) was for the first time successfully synthesized in this work for the repeated use in simultaneous adsorption and photocatalytic degradation of aromatically structured chemical pollutants. The resulting sample was characterized by TEM, XRD, FTIR, TG-DTG, XPS, PL, and VSM. Its photocatalytic activity was evaluated in the photocatalytic degradation of rhodamine B (RhB) under high-pressure mercury lamp irradiation. The results showed that about 63% of RhB was absorbed onto the prepared Fe3O4@SiO2@TiO2/GO nanocomposites by just 30 minute mixing, and after 120 min high-pressure mercury lamp irradiation, about 92.03% of RhB was converted. The photocatalytic degradation followed pseudo first-order reaction with an apparent rate constant of 0.0136 min(-1). Compared with the Fe3O4@SiO2@TiO2 nanoparticles, it exhibits an excellent ability to adsorb aromatic compounds via π-π stacking and a higher photocatalytic activity due to the presence of GO. In addition, the synthesized nanomaterial exhibited good magnetic response and the reusability study suggested that the prepared nanocomposites were stable enough and maintained high degradation rate and catalyst recovery even after five cycles, verifying their potential application in water purification.

Multifunctional nanocomposites constructed from Fe3O4-Au nanoparticle cores and a porous silica shell in the solution phase.

This work is directed towards the synthesis of multifunctional nanoparticles composed of Fe(3)O(4)-Au nanocomposite cores and a porous silica shell (Fe(3)O(4)-Au/pSiO(2)), aimed at ensuring the stability, magnetic, and optical properties of magnetic-gold nanocomposite simultaneously. The prepared Fe(3)O(4)-Au/pSiO(2) core/shell nanoparticles are characterized by means of TEM, N(2) adsorption-desorption isotherms, FTIR, XRD, UV-vis, and VSM. Meanwhile, as an example of the applications, catalytic activity of the porous silica shell-encapsulated Fe(3)O(4)-Au nanoparticles is investigated by choosing a model reaction, reduction of o-nitroaniline to benzenediamine by NaBH(4). Due to the existence of porous silica shells, the reaction with Fe(3)O(4)-Au/pSiO(2) core/shell nanoparticles as a catalyst follows second-order kinetics with the rate constant (k) of about 0.0165 l mol(-1) s(-1), remarkably different from the first-order kinetics with the k of about 0.002 s(-1) for the reduction reaction with the core Fe(3)O(4)-Au nanoparticles as a catalyst.

Synthesis of a novel magnetic drug delivery system composed of doxorubicin-conjugated Fe3O4 nanoparticle cores and a PEG-functionalized porous silica shell.

Coating a layer of PEG functionalized porous silica shell onto doxorubicin-conjugated Fe(3)O(4) nanoparticles, we demonstrated, provides a number of combined advantages in view of the magnetic carrier's therapeutic functionality to treat tumors.