Surface-Enhanced Raman Scattering (SERS) of Nitrothiophenol Isomers Chemisorbed on TiO2

Surface-enhanced Raman scattering (SERS) spectroscopy and density functional theory (DFT) calculations were used to investigate the nature of the charge-transfer (CT) process between nitrothiophenol (NTP) isomers and the n-type semiconductor, TiO₂. The Raman signals of p-NTP and m-NTP that were chemisorbed onto TiO₂ were significantly enhanced with respect to their corresponding neat compounds. In particular, an enhancement factor (EF) of 10²–10³ was observed for both p-NTP and m-NTP, with m-NTP displaying a larger EF compared to p-NTP. The Raman signal of o-NTP on TiO₂ was not detectable, owing to interference from fluorescence emissions. A molecule-to-TiO₂ charge-transfer mechanism was responsible for the enhanced Raman signals observed in p-NTP and m-NTP. This transfer was due to a strong coupling between the adsorbate and the metal oxide, which led to an optically driven CT transition from the HOMO of NTP into the conduction band of TiO₂. Based on the mesomeric effect, the NO₂ group para to the thiol had a stronger electron-withdrawing ability than the NO₂ group at the meta position. A less-efficient CT transition from p-NTP to TiO₂ in the surface complex resulted in a weaker Raman-signal enhancement for p-NTP compared to m-NTP. The DFT calculation determined that the HOMO and the LUMO of NTP bound to TiO₂ were located entirely on the adsorbate and the semiconductor, respectively, thereby supporting the experimental findings that a molecule-to-TiO₂ mechanism was the driving force behind the observed SERS effect.     

Correction to: The replacement of irreducible polynomial and affine mapping for the construction of a strong S-box

Nonlinear Dynamics - In the original publication of the article, Tables 4 and 7 were incorrectly published.     

The replacement of irreducible polynomial and affine mapping for the construction of a strong S-box

Nonlinear Dynamics - Substitution box (S-box) is a critical part of the data encryption and decryption procedures. The primary function of the S-box in advanced encryption standard algorithm is to...     

Polymer-based electrospray device with multiple nozzles to minimize end effect phenomenon

In this paper, “end effect”, which represents the deflection of meniscus of boundary nozzles in an array due to asymmetric electric field and repulsive forces between adjacent nozzles, is experimentally investigated and a polymer-based electrospray device is fabricated and tested to minimize the end effect. For the electrically conductive nozzles of electrospray, the end effect could be reduced by dummy nozzles, through which no liquid is supplied, mounted at the boundary of the array. However, the polymer-based electrospray device can eliminate the end effect without using the dummy dry nozzles due to dielectric characteristic. A novel multiple nozzles of Polymethyl Methacrylate (PMMA)-based electrospray device was successfully fabricated and evaluated for reducing the end effect, showing no deflection of menisci through the boundary nozzles. And ten nozzles device was fabricated and observed to eject liquid jet simultaneously. The electrical current of the spray issued from the nozzles of the polymer-based electrospray device is measured with respect to flow rate and shows a good agreement with the scaling law.     

Mesoporous Manganese Oxide/Lignin-Derived Carbon for High Performance of Supercapacitor Electrodes

This study explores the modification of lignin with surfactants, which can be used as a template to make mesoporous structures, and can also be used in combination with manganese oxide to produce manganese oxide/lignin-derived carbon. Organosolv extraction, using ethanol (70%) at 150 °C, was carried out to extract lignin from oil palm wood. Lignin was then mixed with Pluronic F-127, with and without Mn(NO₃)₂, and then crosslinked with acidic formaldehyde, resulting in a carbon precursor-based modified lignin. Carbonization was carried out at 900 °C to produce lignin-derived carbon and manganese oxide/lignin-derived carbon. The characterization materials included Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope-energy dispersive X-ray (SEM-EDX) mapping, X-ray diffraction (XRD), and N₂-sorption analysis. FTIR curves displayed the vibration bands of lignin and manganese oxide. SEM images exhibited the different morphological characteristics of carbon from LS120% (lignin with a Pluronic surfactant of 120%) and LS120%Mn20% (lignin with a Pluronic of 120% and Mn oxide of 20%). Carbon LS120% (C-LS120%) showed the highest specific surface area of 1425 m²/g with a mean pore size of 3.14 nm. The largest mean pore size of 5.23 nm with a specific surface area of 922 m²/g was exhibited by carbon LS120%-Mn20% (C-LS120%-Mn20%). C-LS120%Mn20% features two phases of Mn oxide crystals. The highest specific capacitance of 345 F/g was exhibited by C-LS120%-Mn20%.     

The novel composite material MOF-[Mg3(BTC)2]/GO/Fe3O4 and its use in slow-release ibuprofen

This study aimed to synthesize a composite material consisting of metal–organic framework based magnesium(II) and benzene-1,3,5-tricarboxylic acid (H₃BTC) and its modification using graphene oxide (GO) and Fe₃O₄. The obtained material (i.e., [Mg₃(BTC)₂]/GO/Fe₃O₄) was studied as a matrix for the slow release of ibuprofen. [Mg₃(BTC)₂]/GO/Fe₃O₄ matrices were synthesized ex situ with the sonochemical method (material 1) and in situ with the solvothermal method (material 2). The obtained materials were completely characterized by X-ray diffraction and Fourier-transform infrared spectroscopy. Based on scanning electron microscopy imaging, the produced materials were spherical. The presence of GO and Fe₃O₄ in material 1 and material 2 reduced the surface area, but it increased the adsorption capacity of ibuprofen up to 94.12%. The magnetic properties of materials 1 and 2 were observed using a vibrating sample magnetometer. These results demonstrate that modification of Fe₃O₄ nanoparticles induces paramagnetic properties in both materials. The presence of this matrix material was able to release ibuprofen up to seven times slower at pH 5.0 and 12 times slower at pH 7.4. An increase in the pH lead to an increase in the concentration of ibuprofen released to 33.31% more than at pH 5.0.     

Transmission characteristics of a microscale dielectric slab waveguide device with a deep groove and an embedded metallodielectric grating at low terahertz frequency

We discuss the transmission characteristics of a microscale dielectric waveguide device with a deep groove and an embedded metallodielectric grating illuminated by a continuous wave of TM and TE modes at low terahertz frequency. To study its performance we solve numerically the corresponding Maxwell equations by means of finite difference time domain method with uniaxial perfectly match layer as its boundary condition. By varying the angle of incident, grating filling factor and refractive index of analyte in the deep groove, it is found that the device exhibits a significant transmission enhancement for the TM mode due to the existence of surface plasmon interaction. We also demonstrate its potential application as a biosensor device.