High specific surface area N-doped activated carbon from hydrothermal carbonization of shaddock peel for the removal of norfloxacin from aqueous solution

A novel N-doped activated carbon (NAC) derived from shaddock peel was investigated to remove norfloxacin (NFX) from aqueous solution. The Box-Behnken central composite design (BBD) was used to optimize the preparation conditions of NAC. The specific surface area of NAC was 2,481.81 m² g^-1, which was obtained at 1,106 K activation temperature, 2.4 h residence time, and 2.3:1 mass ratio of KOH to hydrochar. Moreover, the equilibrium data were perfectly represented by Langmuir and Koble-Corrigan isotherms, and the adsorption process was precisely described by the pseudo-second-order kinetic model. Besides, the adsorption of NFX on NAC was mainly controlled by π-π electron-donor-acceptor (EDA) interaction, hydrophobic effect, hydrogen-bonding, electrostatic interaction and Lewis acid-base effect. The maximum monolayer adsorption capacity of NFX was 746.29 mg g^-1 at 298 K, implying that NAC was a promising adsorbent for the removal of NFX from aqueous solution.

Photopatterning of Carbon Dots in Poly(vinyl alcohol) with Photoacid Generators

Carbon dots (CDs) have drawn considerable attention owing to their attractive photoluminescence, advantageous chemical tolerance, good biocompatibility, and so on. However, it remains challenging to tune their photoluminescence spatially and temporally due to their high photostability. Herein, a viable approach to in-situ dialing the photoluminescence of CDs by using light in the presence of a photoacid generator (PAG, e.g., diphenyliodonium hexafluorophosphate) is demonstrated. Fluorescence quenching occurs upon light irradiation due to the protonation of pyridine and amino nitrogen atoms of CDs according to X-ray photoelectron spectroscopy and cyclic voltammetry. As such, blue, green, and red color fluorescent patterns of CDs are ready to form in poly(vinyl alcohol) by light irradiation under photomask. These patterns not only show a controlled preservation time under room light, but also can be erased on demand by flood UV irradiation, which are promising for advanced anti-counterfeiting such as shelf-life based security and erasable encryption.

Tetracycline removal via adsorption and metal-free catalysis with 3D macroscopic N-doped porous carbon nanosheets: Non-radical mechanism and degradation pathway

Recently, metal-based carbon materials have been verified to be an effective persulfate activator, but secondary pollution caused by metal leaching is inevitable. Hence, a green metal-free 3D macroscopic N-doped porous carbon nanosheets (NPCN) was synthesized successfully. The obtained NPCN showed high adsorption capacity of tetracycline (TC) and excellent persulfate (PS) activation ability, especially when calcined at 700 °C (NPCN-700). The maximum adsorption capacity of NPCN-700 was 121.51 mg/g by H-bonds interactions. Moreover, the adsorption process followed pseudo-second-order kinetics model and Langmuir adsorption isotherm. The large specific surface area (365.27 mg/g) and hierarchical porous structure of NPCN-700 reduced the mass transfer resistance and increased the adsorption capacity. About 96.39% of TC was removed after adding PS. The effective adsorption of the catalyst greatly shortened the time for the target organic molecules to migrate to the catalyst. Moreover, the NPCN-700 demonstrated high reusability with the TC removal rate of 80.23% after 4 cycles. Quenching experiment and electron paramagnetic resonance (EPR) test confirmed the non-radical mechanism dominated by ¹O₂. More importantly, the C = O groups, defects and Graphitic N acted as active sites to generate ¹O₂. Correspondingly, electrochemical measurement revealed the direct electron transfer pathway of TC degradation. Finally, multiple degradation intermediates were recognized by the LC-MS measurement and three possible degradation pathways were proposed. Overall, the prepared NPCN had excellent application prospects for removal of antibiotics due to its remarkable adsorption and catalytic degradation capabilities.

Effect of Functionalization of Reduced Graphene Oxide Coatings with Nitrogen and Sulfur Groups on Their Anti-Corrosion Properties

Electrophoretic production of anticorrosion carbonaceous coatings on copper could be successfully performed by anodic oxidation of negatively charged graphene platelets suspended in an aqueous solution. The various platelets were synthesized by Hummer’s method followed by a hydrothermal reduction in the presence of NH₄SCN which was expected to substitute some parts of graphene structure with nitrogen and sulfur groups. X-ray photoelectron spectroscopy analysis confirmed that the graphene precursors, as well as the coatings, contained typical nitrogen groups, such as pyridinic and pyrrolic, and sulfur groups, such as thiol, thiophene, or C-SO₂. However, due to oxidation during deposition, the qualitative and quantitative composition of the graphene coatings changed relative to the composition of the precursors. In particular, the concentration of nitrogen and sulfur dropped and some thiophene groups were oxidized to C-SO₂. Studies showed the functionalized coatings had a uniform, defect-free, hydrophobic, more adhesive surface than nonmodified films. The corrosion measurements demonstrated that these coatings had better protective properties than the ones without these heteroatoms. This behavior can be assigned to the catalytic activity of nitrogen towards oxidation of C-SO₂ groups to C-SO₃H with oxygen.

Review of the Application of Graphene-Based Coatings as Anticorrosion Layers

Due to the excellent properties of graphene, including flexibility that allows it to adjust to the curvature of the substrate surface, chemical inertness, and impermeability, graphene is used as an anticorrosion layer. In this review, we present the current state-of-the-art in the application of graphene in the field of protective coatings. This review provides detailed discussions about the protective properties of graphene coatings deposited by different methods, graphene-based organic coatings, the modification of graphene-based coatings, and the effects of graphene functionalization on the corrosion resistance of protective coatings.

Experimental and theoretical investigations of four amine derivatives as effective corrosion inhibitors for mild steel in HCl medium

Four amine derivative compounds were synthesized: 2-[(phenylamino)methyl]phenol, 2-{[(4-hydroxyphenyl)amino]methyl}phenol, 2-[(2-hydroxybenzyl)amino]benzonitrile and 2-{[(3-chlorophenyl)amino]methyl}phenol. The structure of the organic molecules was confirmed by FT-IR, ¹³C NMR and ¹H NMR spectroscopy analyses. Their corrosion inhibition performances on mild steel in 1 M HCl were investigated using electrochemical measurements and surface analysis. Scanning electron microscopy analysis confirms the presence on the mild steel surface of a protective film of the as-prepared organic compounds, which depends on the substituent groups. Moreover, density functional theory and molecular dynamics simulation were employed in order to determine the adsorption mechanism and the position of amine derivative molecules towards the mild steel surface in an aggressive solution and to confirm the electrochemical results. The inhibition efficiency (IE) decreases with a decrease in concentration and the adsorption obeyed the Langmuir isotherm. The substitution of the OH group on the aromatic ring by Cl or CN increases IE to 90.23 and 92.56%, respectively. Molecular dynamics simulations attested that the four molecules were adsorbed on the Fe (110) surface in a flat position in the presence of water and HCl with high interaction between the different groups of the inhibitors and mild steel surface.

Four amine derivative compounds were synthesized and used as organic corrosion inhibitors.

Enhancement of thermo-mechanical stability for nanocomposites containing plasma treated carbon nanotubes with an experimental study and molecular dynamics simulations

This study investigated differences in the thermo-mechanical properties of thermosetting polymer EPON 826 nanocomposites reinforced by modified nanofillers. Carbon nanotubes (CNTs) were modified by environmentally friendly plasma treatments. Composites containing various nitrogen doped CNTs were investigated by morphological and structural analysis, which confirmed that they provided better dispersion and stronger interfacial interaction with the epoxy matrix. In addition, the dynamic mechanical behavior and thermal conductivity were analyzed to understand the energy transfer mechanism in the nanocomposites. The thermal and mechanical properties of the Inductively coupled plasma treated CNTs (ICP-CNT) reinforced nanocomposites containing a high concentration of quaternary and pyridinic types were higher than that of mechanical shear force plasma treated CNTs (MSF-CNT). A molecular dynamics (MD) simulation was performed to support the experimental results and confirmed that controlling the type of nitrogen doping groups was important for improving the thermo-mechanical characteristics of CNT/epoxy nanocomposites.

Nitrogen-doped graphene oxide as a catalyst for the oxidation of Rhodamine B by hydrogen peroxide: application to a sensitive fluorometric assay for hydrogen peroxide

The authors report that nitrogen-doped graphene oxide (NGO) catalyzes the oxidative decomposition of the fluorophore Rhodamine B (RhB) by hydrogen peroxide. The catalytic decomposition of hydrogen peroxide yields free hydroxyl radicals that destroy RhB so that the intensity of the yellow fluorescence is reduced. Nitrogen doping enhances the electronic and optical properties and surface chemical reactivities of GO such as widening of bandgap, increase in conductivity, enhanced quenching and adsorbing capabilities etc. The catalytic properties of NGO are attributed to its large specific surface and high electron affinity of nitrogen atoms. The chemical and structural properties of GO and NGO were characterized by XRD, FTIR, SEM, UV-visible and Raman spectroscopies. The method was optimized by varying the concentration of RhB, nitrogen dopant and hydrogen peroxide. The fluorescent probe, best operated at excitation/emission wavelengths of 554/577 nm, allows hydrogen peroxide to be determined in concentrations as low as 94 pM with a linear range spanning from 1 nM to 1 μM. Graphical abstract Schematic illustration of a fluorescence quenching method for the determination of H₂O₂. Upon addition of H₂O₂, nitrogen-doped graphene oxide (NGO) catalyzes the oxidation of Rhodamine B dye due to hydroxyl radical generation, which leads to a sensitive quenchometric methd for H₂ O₂.

Sonochemically N-functionalized graphene oxide towards optically active photoluminescent bioscaffold

Herein, Nitrogen functionalized graphene oxide (N-f-GrO) has been synthesized using the sonochemical method. 2-Aminopyrimidine (APD) was used as a precursor for covalent functionalization with graphene oxide [f-(APD)GrO] as N-f-GrO which was ascertained with XPS. The involvement of arylamine group and formation of covalent bond over GrO surface was confirmed with high resolution C1s spectrum of f-(APD)GrO. Also, the signature of N1s peak in the survey spectrum of f-(APD)GrO has endorsed the surface modification of GrO through covalent functionalization. A bathochromic shift was observed for f-(APD)GrO in UV and enhanced weight loss of 91.39% at 191.80 °C, confirms a facile functionalization of GrO via formation of amide bond, where the terminal -OH portal of carboxylic group is substituted by 2-Aminopyrimidine. Moreover, the formation of f-(APD)GrO was investigated with various analytical techniques like Raman, XRD and FTIR. The surface morphology and topography have been understood by using HRTEM/SAED, AFM, and SEM analysis. The synthesized f-(APD)GrO shows potential optically active photoluminescence properties and higher potency towards biological insight. The identified photoluminescence (PL) peaks at 3.78, 3.21 2.01 and 1.64 eV indicate photon emission including an orange optical transition at 2.01 eV. The multiple peaks in a PL spectrum are due to radiative and non-radiative recombinations which are also associated with excess hole (h⁺)-electron (e^-) trapping on the surface to restrict the recombinations of e^- and h⁺. The biological activity of N-f-GrO has been explored with Sulforhodamine B (SRB) assay on HaCaT and Vero cell lines. The concentration-dependent cell viabilities have been observed a maximum at 20 µg/ml for HaCaT and at 10 µg/ml for Vero cell lines at testing concentration range of 10-80 μg mL^-1. The significant morphological impact on cell lines confirms the cytocompatibility behaviour. Therefore, the synergistic impact of various properties of f-(APD)GrO can be further explored to study its significance as nanocarrier for photosensitive biomedical response.

B, Lal C. Praseodymium-decorated graphene oxide as a corrosion inhibitor in acidic media for the magnesium AZ31 alloy

In the present work, Pr-decorated graphene oxide was synthesized and tested as a corrosion barrier layer in acidic media for the magnesium AZ31 alloy. The morphology, composition and structure of Pr-decorated graphene oxide sheets were characterized via HRTEM, FESEM, Raman, XRD, DLS, UV and FTIR studies. The corrosion inhibition efficiency on the alloy surface was monitored via microstructural and electrochemical methods. The results indicate that Pr-decorated graphene oxide provides improved protection for the Mg AZ31 alloy compared to conventional epoxy coatings. The proposed mechanism arises from a combination of the barrier activities of the composite, GO + Pr, and the epoxy coating on the Mg alloy in acidic media.

The Mg alloys 111 surface is covered by the praseodymium decorated graphene oxide sheet, and (A) & (B) indicates ions diffusion control (C) indicates epoxy coating failure.

Isoxazolidine derivatives as corrosion inhibitors for low carbon steel in HCl solution: experimental, theoretical and effect of KI studies

Two isoxazolidine derivatives (BDMTI and HMBTI) were synthesized and characterized using FTIR, C-NMR, H-NMR and elemental analysis and evaluated as corrosion inhibitors for X60 steel in 1 M HCl solution.

N,N'-Dialkylcystine Gemini and Monomeric N-Alkyl Cysteine Surfactants as Corrosion Inhibitors on Mild Steel Corrosion in 1 M HCl Solution: A Comparative Study

Gemini surfactant, N,N'-dialkylcystine 2(C₁₂Cys), derived from cystine, and a monomeric N-alkyl cysteine counterpart, (C₁₂Cys), were synthesized and purified. The characterization of surfactants 2(C₁₂Cys) and (C₁₂Cys) was made by Fourier transform infrared, ¹H NMR, and elemental analysis. The effect of 2(C₁₂Cys) and (C₁₂Cys) on mild steel (MS) corrosion in 1 M HCl solution was explored as a function of their concentration and electrolyte temperature by means of gravimetric and electrochemical experiments (potentiodynamic polarization and Electrochemical impedance spectroscopy), surface analytical techniques (scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDAX) and atomic force microscopy (AFM)) and theoretical study. The investigated compounds exhibited surface active properties and performed as good inhibitors for corrosion control of mild steel (MS) in acid solution. However, compared to monomeric (C₁₂Cys), Gemini surfactant 2(C₁₂Cys) showed high corrosion inhibiting ability at very low concentration. The EIS results revealed a greater charge transfer resistance in 2(C₁₂Cys) solution compared to that in (C₁₂Cys) solution. SEM/EDAX observations validate the development of an inhibitive film by the adsorbed molecules of surfactant on the MS surface. The AFM micrographs supported the SEM/EDAX results and exhibited a lowering in the roughness of the corroded MS surface in the presence of both (C₁₂Cys) and 2(C₁₂Cys) surfactants. Further, quantum chemical calculations and Monte Carlo simulations were used to study the dependence of corrosion inhibiting efficacy on the molecular structure and adsorption strength.

Experimental and theoretical studies on inhibition of mild steel corrosion by some synthesized polyurethane tri-block co-polymers

Polyurethane based tri-block copolymers namely poly(N-vinylpyrrolidone)-b-polyurethane-b-poly(N-vinylpyrrolidone) (PNVP-PU) and poly(dimethylaminoethylmethacrylate)-b-polyurethane-b-poly(dimethylaminoethylmethacrylate) (PDMAEMA-PU) were synthesized through atom transfer radical polymerization (ATRP) mechanism. The synthesized polymers were characterized using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) methods. The corrosion inhibition performances of the compounds were investigated on mild steel (MS) in 0.5 M H₂SO₄ medium using electrochemical measurements, surface analysis, quantum chemical calculations and molecular dynamic simulations (MDS). Potentiodynamic polarization (PDP) measurements revealed that the polymers are mixed-type corrosion inhibitors. Electrochemical impedance spectroscopy (EIS) measurements showed that the polymers inhibit MS corrosion by adsorbing on MS surface to form pseudo-capacitive interface. The inhibitive effects of the polymers increase with increasing concentration and decrease with increasing temperature. The adsorption of both the polymers on MS surface obey the Langmuir adsorption isotherm and involves both physisorption and chemisorption mechanisms. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed that the polymers formed protective film on MS surface and shield it from direct acid attack. Quantum chemical calculations and molecular dynamic simulations studies corroborate experimental results.

Fabrication of stable homogeneous superhydrophobic HDPE/graphene oxide surfaces on zinc substrates

Illustration of the preparation method of superhydrophobic surfaces on zinc substrates.

Carbohydrate compounds as green corrosion inhibitors: electrochemical, XPS, DFT and molecular dynamics simulation studies

Corrosion inhibition effect of 5,6-bis(2-(1H-benzo[d]imidazol-2-yl)hydrazono)hexane-1,2,3,4-tetraol (BIHT) and 5,6-bis(2-(1-methyl-1H-imidazol-2-yl)hydrazono)hexane-1,2,3,4-tetraol (MIHT) on N80 steel in 15% HCl was measured by electrochemical method.

A promising nanocomposite from CNTs and nano-ceria: nanostructured fillers in polyurethane coatings for surface protection

The balanced combination of nanostructured carbon materials and metal oxide nanoparticles has been considered as an efficient reinforcement material in developing next-generation multifunctional coatings.