Ultrathin Sulfonated Mesoporous Silica Film with Well-Ordered Perpendicular Mesochannels: In-Situ Preparation, Characterization and Permselectivity

In this paper, a new type of ultrathin sulfonated mesoporous silica film (SMSF) with well-ordered perpendicular mesochannels was in-situ synthesized by Stöber approach and co-condensation method. The mesostructure of the synthesized SMSF was characterized. The results of small-angle XRD, high-resolution TEM, and cyclic voltammetry (CV) exhibited that, after loading of MPTMS, SMSF had an ordered mesostructure with a perpendicular orientation and open ends. SEM showed that SMSF could be entirely transferred and easily handled. FT-IR presented that sulfonic groups were successfully added to the surface of the nanochannels of silica film. Compared with mesoporous silica film (MSF) and commercial cation exchange membrane (CEM), SMSF had the highest permselectivity. The permselectivity of SMSF was not lined with the loading of the sulfonic groups (–SO3H). The highest permselectivity of SMSF to Na[Formula: see text] was 94% when the loading of MPTMS was 5.98% (wt.%). SMSF is a promising material in the application of salinity gradient energy harvest.

Recycling of the Diamond-wire Saw Powder by Ni-catalyzed Nitridation to Prepare Si3N4

In this paper, the acceleration of nickel (Ni) in the direct nitridation process of the diamond-wire saw powder (DWSP) was investigated. The DWSP doped with Ni additives were nitrided at different temperatures. To study the mechanism of accelerated nitridation, the thermodynamics of Si-O-N-Ni was analyzed by FactSage 7.2 and single-crystal silicon blocks were also nitrided instead of the DWSP. The results revealed that Ni decreased the nitridation temperature at which the DWSP began to gain significant weight and exhibited an excellent accelerating effect on the nitridation of the DWSP. At 1300℃, the DWSP containing 2.0 wt.% Ni additives had been completely nitrided within 2 h, whereas the DWSP without Ni additives had not been nitrided yet. Based on the equivalent substitution experiment, it could be conducted that the presence of Ni additives accelerated the nitridation and promoted the formation of the α-Si3N4 nanorods through facilitating the generation of the SiO(g) and destructing the silica film on the surface of silicon at lower temperature. Meanwhile, Ni additives also played an important part in the growth of α-Si3N4 nanorods by forming liquid Ni-Si alloy in the product.

Surface Pattern over a Thick Silica Film to Realize Passive Radiative Cooling

Passive radiative cooling, which cools an item without any electrical input, has drawn much attention in recent years. In many radiative coolers, silica is widely used due to its high emissivity in the mid-infrared region. However, the performance of a bare silica film is poor due to the occurrence of an emitting dip (about 30% emissivity) in the atmospheric transparent window (8–13 μm). In this work, we demonstrate that the emissivity of silica film can be improved by sculpturing structures on its surface. According to our simulation, over 90% emissivity can be achieved at 8–13 μm when periodical silica deep grating is applied on a plane silica film. With the high emissivity at the atmospheric transparent window and the extremely low absorption in the solar spectrum, the structure has excellent cooling performance (about 100 W/m2). The enhancement is because of the coupling between the incident light with the surface modes. Compared with most present radiative coolers, the proposed cooler is much easier to be fabricated. However, 1-D gratings are sensitive to incident polarization, which leads to a degradation in cooling performance. To solve this problem, we further propose another radiative cooler based on a silica cylinder array. The new cooler’s insensitivity to polarization angle and its average emissivity in the atmospheric transparent window is about 98%. Near-unit emissivity and their simple structures enable the two coolers to be applied in real cooling systems.

Rapid and sensitive determination of doxorubicin in human whole blood by vertically-ordered mesoporous silica film modified electrochemically pretreated glassy carbon electrodes

Direct and accurate detection of doxorubicin (DOX) in unprocessed human whole blood is of vital importance in medical diagnosis and monitoring.

Vertically oriented mesoporous silica film modified fluorine-doped tin oxide electrode for enhanced electrochemiluminescence detection of lidocaine in serum

Sensitive detection of lidocaine in serum is realized using enhanced electrochemiluminescence based on a vertically oriented mesoporous silica film modified fluorine-doped tin oxide electrode.

Hybrid guided space-time optical modes in unpatterned films

Light is confined transversely and delivered axially in a waveguide. However, waveguides are lossy static structures whose modal characteristics are fundamentally determined by their boundary conditions. Here we show that unpatterned planar waveguides can provide low-loss two-dimensional waveguiding by using space-time wave packets, which are unique one-dimensional propagation-invariant pulsed optical beams. We observe hybrid guided space-time modes that are index-guided in one transverse dimension and localized along the unbounded dimension. We confirm that these fields enable overriding the boundary conditions by varying post-fabrication the group index of the fundamental mode in a 2-μm-thick, 25-mm-long silica film, achieved by modifying the field’s spatio-temporal structure. Tunability of the group index over an unprecedented range from 1.26 to 1.77 is verified while maintaining a spectrally flat zero-dispersion profile. Our work paves the way to utilizing space-time wave packets in on-chip platforms, and enable phase-matching strategies that circumvent restrictions due to intrinsic material properties.

Structural and optical properties of Zn-implanted silica: effect of fluence and annealing

The phase-structural composition of a silica film grown on Si substrate implanted with Zn ions at room temperature with different fluences has been studied using transmission electron microscopy and electron diffraction. The small clusters (1–2 nm) and the large clusters (5–7 nm) have been formed in as-implanted silica films with the Zn concentration of 6–7 at % and 16–18 at %, respectively. Furnace annealing at 750 °С for two hours results both in the formation of the orthorhombic Zn2SiO4 phase (space group R-3) in the case of low fluence (5 · 1016 cm–2) and in the formation of the cubic ZnO phase (space group F-43m) in the case of high fluence (1 · 1017 cm–2). It has been shown that impurity loss during implantation and subsequent annealing increase with fluence of implanted ions. The fraction of Zn atoms in clusters has been estimated to be 15 % and 18 % for fluences (5 · 1016 cm–2) and (1 · 1017 cm–2), respectively. It has been shown that residual Zn impurities dissolved in silica matrix noticeably suppress the light-emitting properties of silica with embedded Zn2SiO4 and ZnO nanocrystals.