Synergetic signal amplification of multi-walled carbon nanotubes-Fe3O4 hybrid and trimethyloctadecylammonium bromide as a highly sensitive detection platform for tetrabromobisphenol A

Quantitative SERS Detection of TBBPA in Electronic Plastic Based on Hydrophobic Cu-Ag Chips

Tetrabromobisphenol A (TBBPA) was one of the most widely used brominated flame retardants. However, it easily contaminates nature and harms the environment and human health during its production and use. Therefore, it is necessary to strictly control the content of TBBPA in electronics. Surface-enhanced Raman spectroscopy has the advantages of being fast and sensitive, but it is difficult to obtain the SERS spectra of TBBPA because the hydrophobic TBBPA molecule is difficult to approach with the hydrophilic surface of common noble metal SERS substrates. In the present work, a hydrophobic Cu-Ag chip was developed for the SERS detection of TBBPA. The integration of the hydrophobic interaction and the Ag-Br bonding promoted the adsorption of TBBPA on the Cu-Ag chip, allowing for SERS detection. It was observed that both the hydrophobicity and bimetallic composition of the Cu-Ag chip played important roles in the SERS detection of TBBPA. Under the optimized conditions, the low limit of detection of the established SERS method for TBBPA was 0.01 mg L^-1, within a linear range of 0.1-10 mg L^-1. Combined with ultrasonic-assisted extraction, the substrate could be used for the quantitative determination of TBBPA in electronic products. Compared with the HPLC-UV method used as a national standard, the relative error of the SERS method for quantifying the TBBPA content in a mouse cable and shell was ±3% and ±7.7%, respectively. According to the SERS results, the recovery of TBBPA in the spiked mouse shell was 95.6%.

Optical Absorption Investigations for efficient Crystal Violet Dye removal from wastewater via Carbon nanotubes: Montmorillonite based Nanocomposite

The current study reports a facile method to fabricate functionalized multi-walled carbon nanotubes and montmorillonite clay mineral-based nano-composite matrix and its detailed characterization using spectroscopic and morphological techniques. The nanocomposites have been studied for their potential applications in the treatment of contaminated water using batch adsorption studies. The investigations conducted using optical absorption spectroscopic measurements for the adsorption process indicate that the nanocomposite matrix can effectively remove almost 98% of the dye from aqueous solution. The nanocomposites have showed fast and strong adsorption behaviour for the dye with the maximum adsorption capacity (q_m ) of ~ 467.3 mg g^-1 in 25 min. The experimental data at equilibrium were also correlated with the theoretical adsorption isotherm and kinetic models. The results demonstrate that the experimental data fits well to the Freundlich adsorption isotherm model and conforms to second order kinetics. Furthermore, the nanocomposite exhibits good recyclability without any marked decrease in the adsorption performance even after five adsorption cycles of usage which indicates its potential application as reusable adsorbent for the efficient removal of hazardous dyes from contaminated water.

A Low Cost Fe3O4-Activated Biochar Electrode Sensor by Resource Utilization of Excess Sludge for Detecting Tetrabromobisphenol A

Owing to its ubiquity in natural water systems and the high toxicity of its accumulation in the human body, it is essential to develop simple and low-cost electrochemical sensors for the determination of 3,3',5,5'-tetrabromobisphenol A (TBBPA). In this work, Fe3O4-activated biochar, which is based on excess sludge, was prepared and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and BET analysis to analyze its basic features. Subsequently, it was used to fabricate an electrochemical sensor for the detection of TBBPA. The electrochemical test results revealed that the Fe3O4-activated biochar film exhibited a larger active surface area, a lower charge transfer resistance and a higher accumulation efficiency toward TBBPA. Consequently, the peak current of TBBPA was significantly enhanced on the surface of the Fe3O4-activated biochar. The TBBPA sensing platform developed using the Fe3O4-activated biochar composite film, with relatively a lower detection limit (3.2 nM) and a wider linear range (5-1000 nM), was successfully utilized to determine TBBPA levels in water samples. In summary, the effective application of Fe3O4-activated biochar provided eco-friendly and sustainable materials for the development of a desirable high-sensitivity sensor for TBBPA detection.

A Novel Electrochemical Sensor Based on Au-rGO Nanocomposite Decorated with Poly(L-cysteine) for Determination of Paracetamol

Background:

Paracetamol is a common antipyretic and analgesic drug, but its excessive intake can accumulate toxic metabolites and cause kidney and liver damage, so it is critical to determine the content of paracetamol for clinical diagnosis and dose use.

Methods:

Au-reduced graphene oxide (Au-rGO) nanocomposite decorated with poly(L-cysteine) on carbon paste electrode was fabricated for the determination of paracetamol. Au-rGO was first coelectrodeposited on the carbon paste electrode surface. Afterwards, L-cysteine was electropolymerized to fabricate the Au-rGO/poly(L-cysteine) modified carbon paste electrode. Scanning electron microscope was used to characterize the morphology of Au-rGO and poly(L-cysteine)/Au-rGO. The electrochemical properties of the sensor were studied by cyclic voltammetry and differential pulse voltammetry.

Results:

After exploring the optimal conditions, the sensor showed a wide linear response for paracetamol detection in the range of 1-200 μM with a detection limit of 0.5 μM (S/N = 3).

Conclusion:

The fabricated sensor demonstrated good sensitivity with rapid detection capacity in real samples.

Synthesis of self-assembled spindle-like CePO4 with electrochemical sensing performance

Three different morphologies of CePO₄ nanocrystals (rods, columns, and spindle-like assembled nanosheets), spindle-like LaPO₄, spindle-like PrPO₄, and TbPO₄ microspheres were successfully synthesized using a hydrothermal method.

Efficient Removal of Pb(II) and Cd(II) from Industrial Mine Water by a Hierarchical MoS2/SH-MWCNT Nanocomposite

In this study, we investigate the adsorption capability of molybdenum sulfide (MoS₂)/thiol-functionalized multiwalled carbon nanotube (SH-MWCNT) nanocomposite for rapid and efficient removal of heavy metals [Pb(II) and Cd(II)] from industrial mine water. The MoS₂/SH-MWCNT nanocomposite was synthesized by acid treatment and sulfurization of MWCNTs followed by a facile hydrothermal reaction technique using sodium molybdate and diethyldithiocarbamate as MoS₂ precursors. Morphological and chemical features of the nanocomposite material were studied using various characterization techniques. Furthermore, the effects of adsorbent (MoS₂/SH-MWCNT nanocomposite) concentration, contact time, initial concentration of heavy-metal ions, and reaction temperature were examined to determine the efficiency of the adsorption process in batch adsorption experiments. Kinetics and isotherm studies showed that the adsorption process followed pseudo-second-order and Freundlich adsorption isotherm models, respectively. Thermodynamic parameters calculated using van't Hoff plots show the spontaneity and endothermic nature of adsorption. MoS₂/SH-MWCNT nanocomposite demonstrates a high adsorption capacity for Pb(II) (90.0 mg g^-1) and Cd(II) (66.6 mg g^-1) following ion-exchange and electrostatic interactions. Metal-sulfur complex formation was identified as the key contributor for adsorption of heavy-metal ions followed by electrostatic interactions for multilayer adsorption. Transformation of adsorbent into PbMoO_4-x S _x and CdMoO_4-x S _x complex because of the adsorption process was confirmed by X-ray diffraction and scanning electron microscopy-energy-dispersive spectrometry. The spent adsorbent can further be used for photocatalytic and electrochemical applications; therefore, the generated secondary byproducts can also be employed for other purposes.

The mechanical properties, microstructures and mechanism of carbon nanotube-reinforced oil well cement-based nanocomposites

High performance cement-based nanocomposites were successfully fabricated through the use of oil well cement filled with multiwalled carbon nanotubes (MWCNTs) as reinforcements. The dispersibilities of four dispersing agents for the MWCNTs were investigated and compared. The dispersed morphologies and structural characteristics of the MWCNTs were analyzed via TEM, FTIR and Raman spectroscopy studies. The effects of MWCNT addition on the rheological behavior and fluidity of oil well cement slurry were discussed. The mechanical properties of the cement-based nanocomposites with different MWCNT content values and different curing ages were explored and analyzed. Furthermore, the microstructures of the MWCNT reinforced cementitious nanocomposites were characterized via XRD, SEM, EDS, total porosity and pore size distribution studies. The results demonstrated that the 28 day compressive strength and 28 day flexural strength of the 0.05 wt% MWCNT cementitious nanocomposite increased by 37.50% and 45.79%, respectively, compared with a pure cement matrix. The elastic moduli of a 0.05 wt% MWCNT cementitious sample declined by 19.07% and 35.39% under uniaxial and triaxial stress, respectively. XRD and pore structure analysis indicated that the MWCNTs could accelerate the hydration process, increase the amount of hydration products and optimize the pore size distribution within the matrix. Additionally, crack bridging, pulling out, network filling and a calcium-silicate-hydrate (C–S–H) phase were exhibited by SEM images. Meanwhile, the reinforcing and toughening mechanism of MWCNTs was also discussed; these had a beneficial influence on the mechanical properties.

The reinforcing and toughening mechanism of MWCNTs in cementitious nanocomposites under the external load.