Journal of Molecular and Engineering Materials

The biological sensing interface on the active area of a piezo transducer is responsible for the sensitivity, specificity, reusability, and reproducibility of these devices. Among the approaches used to functionalize piezo transducers, mixed self-assembled monolayers (MSAMs) are one of the most successful, given that they allow the obtaining of semi-crystalline molecular arrays and the arrangement of a bioreceptor on the surface. But, to deploy MSAMs on a substrate effectively, one must optimize and characterize the structural ratio between them and the bioreceptor. In this paper, we developed a molecular model of the interaction between Bovine Serum Albumin (BSA) and MSAMs-functionalized gold substrates. First, we evaluated the conditions for the functionalization of the substrates and found that a 50:1 16-mercaptohexadecaonic acid (MHDA) to 11 mercapto-1-undecanol (MUA) ratio produced the best features on the surface. We also evaluated the specific conditions to immobilize BSA on MSAMs (using the afore-established ratio) via Atomic Force Microscopy (AFM), and then on a 10MHz quartz crystal microbalance (QCM), and with the data obtained we concluded that a structural ratio of 0.005 (MSAM/BSA) is obtained when 1$\mu$M MHDA and 200$\mu$g/mL BSA were used, provided the most suitable conditions for the functionalization of a piezo transducer.

This work proposes the synthesis of nanocrystalline calcium oxide (CaO) pure and doped with different concentrations of lithium (Li${}^{2+}$) ions by sol–gel process. Calcium nitrate (Ca(NO${}_3{)}_2\cdot$4H₂O; 99.99%) and lithium nitrate (LiNO₃; 99.99%) were used as precursors. The synthesized powders were characterized by several techniques such as: UV-Vis transmission spectroscopy, Fourier Transform Infra-red spectroscopy (FT-IR) and X-ray diffraction (XRD). The main objective of this paper is to study the influence of lithium (Li${}^{2+}$ ratio) on the structural and optical properties of synthesized powders. The band gap values decreased with the increasing of Li${}^{2+}$ ions in CaO lattice; the slight change in the band gap was directly related to the energy transfer between the CaO excited states and the 2s levels of Li${}^{2+}$ ions. The influence of Li${}^{2+}$ doping on the physical properties of CaO nanocrystalline will be studied for the first time in this work; no literature has previously published this kind of impurities.

The microstructural change of a thermal oxidation on a PM2000 superalloy was investigated after a 48 h isothermal heat-treatment. The oxides (transitions aluminas, $\alpha$-alumina and mixed oxides) were characterized using the Raman spectroscopy, the Photoluminescence (PL) spectroscopy, MEB observations and the X-ray diffraction for temperatures between 600^°C and 1200^°C. The X-ray diffraction results under conventional incidence conditions make it possible to estimate the crystallites size and the specific surfaces of the $\alpha$-alumina. The PL analyses at various excitation wavelengths (200nm, 234nm, 326nm and 532nm) provide important information on the existing defects (intrinsic and extrinsic) according to the oxidation temperature. The Raman spectroscopy (${\lambda }_{\mathrm{\text{exc}}}=632$.18nm) gives the various signatures of the various alumina generated ($\gamma$, $\delta ∕\theta$, $\theta$ and $\alpha$-Al₂O₃).

NiCo₂S₄/CNTs (NCS/CNTs) hybrid nanostructures have been synthesized by a facile one-step solvothermal method with varying content of CNTs. The structure and morphology of the synthesized NCS/CNTs hybrid revealed the formation of platelets anchored on the CNT matrix. When evaluated as electrode materials for supercapacitor, the as-synthesized NCS/CNT-1 hybrid (with 1% of CNT) manifested remarkable specific capacitance of 1690Fg${}^{-1}$ at the current density of 5Ag${}^{-1}$. More importantly, an asymmetric supercapacitor (ASC) assembled based on NCS/CNT-1 as positive electrode and carbon nanotube paper (CNP) as a negative electrode delivered high energy density of 58Whkg${}^{-1}$ under power density of 8kWkg${}^{-1}$. Furthermore, the ASC device exhibited high cycling stability and 77.7% of initial specific capacitance retention after 7000 charge–discharge cycles at a current density of 8Ag${}^{-1}$. The large enhancement in the electrochemical performance is attributed to the benefits of the nanostructured architecture, including good mechanical stability, high electrical conductivity as well as buffering for the volume changes during charge–discharge process. These convincing results show that NCS/CNTs hybrid nanostructures are promising electrode materials for high energy density supercapacitors (SCs).

Excellent cycling stability along with a high specific capacitance of the electrode material is the primary requirement for supercapacitor (SC) in recent years. Exceptionally simple and cost-effective solution process is employed for the first time to prepare $\alpha$-MnO₂/rGO composites, in which KMnO₄ content varies from (2mg, 4mg, 6mg and 8mg). The morphological analysis showed that $\alpha$-MnO₂/rGO composites possess nanorod like morphology and were fully covered with rGO sheet. Among all composites, the sample with 6mg content of KMnO₄ denoted as $\alpha$-MnO₂/rGO composite (S–3) showed excellent supercapacitive performance with a specific capacitance of 720F/g at a current density of 4 A g${}^{-1}$ with excellent cycling stability of 93% after 2000 cycles. Furthermore, these nanocomposites showed excellent supercapacitive properties with specific capacitances of 720–498 F/g at the current density of 4 A g${}^{-1}$ with cycling stabilities of 71%, 68% and 60%, respectively.