A detailed investigation of the structural changes of lithium borate (LiB) glass 25Li₂O-(75 - x)B₂O₃ was conducted in the absence and presence of lead(II) oxide or aluminum oxide (x = 10 mol %) glass modifiers. X-ray diffraction (XRD), Fourier transform infrared (FTIR), and electron paramagnetic resonance (EPR) spectroscopy were used to explore the structural properties of LiB glass by incorporating trace amounts of manganese(III) oxide (0.00-0.25 mol %) as a probe. Differential thermal analysis and XRD results for the glasses and their ceramics confirmed the integration of aluminum atoms into the glass framework by forming a lithium aluminum boron oxide Li₂(AlB₅O₁₀) crystalline phase. Lead atoms were located interstitially, which disordered the borate glass structure and produced a lithium tetraborate crystalline phase. Semiempirical modeling of the glass structures was conducted to estimate the fundamental vibrational modes of the glass materials using a parametric method 3 (PM3MM) with molecular mechanics corrections to elucidate the geometry of the borate (BO₃) groups and their possible vibrational modes. Our analysis revised the conventional representation of the tetrahedral BO₄ units, which were not observed, to "distorted-trigonal" BO₃ groups and associated with nonbridging oxygen (NBO) atoms. EPR spectroscopy established a link between the NBO in oxides and the well-defined peak at g-factor ∼4.2 in glass materials, which had been assigned to iron(III) ions according to the literature.

An ultra-sensitive sensor of dopamine is introduced. The sensor is constructed by encapsulating platinum nanoparticles (PtNPs) between reduced graphene oxide (GR) nanosheets. The sandwiched PtNPs between GR layers acted as a spacer to prevent aggregation and provided a fine connection between the GR nanosheets to provide fast charge transfer. This specific orientation of the GR nanosheets and PtNPs on the graphite pencil electrode (GPE) substantially improved the electrocatalytic activity of the sensor. The synthesized graphene oxide and the fabricated sensor were comprehensively characterized by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, field emission-scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square wave voltammetry (SWV). The value of the charge transfer coefficient (α), apparent heterogeneous electron transfer rate constant (k_s), and electroactive surface area for dopamine were found to be about 0.57, 8.99 s⁻¹, and 0.81 cm², respectively. The developed sensor is highly sensitive towards dopamine, and the detection limit is 9.0 nM. The sensor response is linear for dopamine concentration from 0.06 to 20 μM (R² = 0.9991). The behavior of the sensor for dopamine in the presence of a high concentration of L(+) Ascorbic acid and other potential interferents was satisfactory. High recovery percentage between 90% and 105% in the human urine sample, good reproducibility, and facile fabrication of the electrode make it a good candidate for dopamine sensing.