Preparation of poly (methacrylic acid)/graphene oxide aerogel as solid-phase extraction adsorbent for extraction and determination of dopamine and tyrosine in urine of patients with depression

Colorimetric discrimination and spectroscopic detection of tyrosine enantiomers based on melamine induced aggregation of l-cysteine/Au nanoparticles

Au nanoparticles (AuNPs) are decorated by l-cysteine (L-Cys), and the resultant chiral L-Cys/AuNPs can be used for colorimetric discrimination and spectroscopic detection of the tyrosine (Tyr) enantiomers. Melamine (Mel) can induce the aggregation of the L-Cys/AuNPs through ligand exchange, leading to a distinct color change from wine red to purple. Owing to the same rotatory direction of L-Cys/AuNPs and L-Tyr, the L-Cys/AuNPs exhibit a significantly higher binding affinity toward L-Tyr than D-Tyr, and thus the Mel induced aggregation of the L-Cys/AuNPs is greatly alleviated by the protection from the L-Tyr protective layer. Therefore, the Tyr enantiomers can be simply discriminated by naked eyes. In addition, the absorbance of the aggregated L-Cys/AuNPs at ∼630 nm increases linearly with decreasing concentrations of L-Tyr ranging from 10 nM to 1 mM due to the weakened protection effect from L-Tyr, and thus spectroscopic detection of L-Tyr can also be accomplished by the developed L-Cys/AuNPs with a limit of detection (LOD) of 5.3 nM.

Development of a three-dimensional porous ionic liquid-chitosan-graphene oxide aerogel for efficient extraction and detection of polyhalogenated carbazoles in sediment samples

The three-dimensional porous ionic liquid-chitosan-graphene oxide aerogel (IL-CS-GOA) monolithic adsorbent with a through-hole structure was prepared using natural chitosan (CS) as the skeletal framework, graphene oxide (GO) as the support to provide mechanical strength, and ionic liquid (IL) as the porogen and modifier. The resulting IL-CS-GOA demonstrated a fluffy and porous structure with various pore sizes and excellent regeneration capability (over six cycles). Its specific surface area exceeded that of CS-GOA and IL-GOA by more than 7 times, enhancing its polyhalogenated carbazoles (PHCZs) adsorption capacity. Within 5 min, IL-CS-GOA (1.0 mg) exhibited adsorption amounts of 539 ng mg-1 for 3-bromocarbazole (3-BCZ), 716 ng mg-1 for 2,7-dibromocarbazole (2,7-BCZ), and 798 ng mg-1 for 1,3,6,8-tetrabromocarbazole (1,3,6,8-BCZ), showcasing its rapid mass transfer and high adsorption capabilities. IL-CS-GOA was utilized as the adsorbent for glass dropper extraction (GDE) in conjunction with gas chromatography-mass spectrometry (GC-MS/MS), to develop a highly efficient and accurate method for determining PHCZs in sediments. Under optimal conditions, the established method exhibited a wide linear range (0.4-250 ng g-1, r ≥ 0.9990), low detection limits (0.04-0.24 ng g-1), and satisfactory recoveries (80.5 %-93.8 %), enabling the accurate and rapid detection of PHCZs in sediment samples. This study presents a novel approach for creating three-dimensional porous aerogels, introduces a new form of sample pretreatment using GDE with a monolithic adsorbent, and offers a new method for the determination of PHCZs in environmental matrices.

Highly sensitive and simultaneous detection of ascorbic acid, dopamine, and uric acid using Pt@g-C3N4/N-CNTs nanocomposites

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is crucial for understanding and managing various illnesses. In this research, Pt@g-C3N4 nanoparticles were synthesized via hydrothermal method and combined with N-doped carbon nanotubes (N-CNTs). The Pt@g-C3N4/N-CNTs-modified glassy carbon (GC) electrode was fabricated as an electrochemical sensor for the determination of AA, DA, and UA. The linear response range of AA, DA, and UA in the optimal condition was 100-3,000 μM, 1-100 μM, and 2-215 μM boasting a low detection limit (S/N = 3) of 29.44 μM (AA), 0.21 μM (UA), and 2.99 μM (DA), respectively. Additionally, the recoveries of AA, DA, and UA in serum sample were 100.4%-106.7%. These results corroborate the feasibility of the proposed method for the simultaneous, sensitive, and reliable detection of AA, DA, and UA. Our Pt@g-C3N4/N-CNTs/GC electrode can provide a potential strategy for disease diagnosis and health monitoring in clinical settings.

Sonochemical synthesis of lanthanum ferrite nanoparticle-decorated carbon nanotubes for simultaneous electrochemical determination of acetaminophen and dopamine

A new nanocomposite consisting of lanthanum ferrite nanoparticles (LaFeO3 NPs) integrated with carbon nanotubes (CNTs) was fabricated via facile sonochemical approach. The engineered nanocomposite was applied to simultaneously determine acetaminophen (ACP) and dopamine (DA) in a binary mixture. The LaFeO3 NPs@CNT probe possesses several advantages such as superior conductivity, large surface area, and more active sites, improving its electrocatalytic activity towards ACP and DA. Under optimized conditions, the anodic peak currents (Ipa) linearly increased with increasing concentration of ACP and DA in the range 0.069-210 µM and 0.15-210 µM, respectively. The sensitivity of LaFeO3 NPs@CNTs/glassy carbon electrode (GCE) for detecting ACP and DA is 7.456 and 5.980 μA·μM-1·cm-2, respectively. The detection limits (S/N = 3) for ACP and DA are 0.02 μM and 0.05 μM, respectively. Advantages of LaFeO3 NPs@CNTs/GCE for the detection of ACP and DA include wide linear ranges, low-detection limits, good selectivity, and long-term stability. The as-fabricated electrode was applied to determine ACP and DA in pharmaceutical formulations and human serum samples with recoveries ranging from 97.7 to 103.3% and an RSD that did not exceed 3.7%, confirming the suitability of the proposed sensor for the determination of ACP and DA in real samples. This study not only presents promising opportunities for enhancing the sensitivity and stability of electrochemical sensors used in the detection of bioanalytes but also significantly contributes to the progress of unique and comprehensive biochemical detection methodologies.

Developing magnetic functionalized dendritic fibrous mesoporous silica as advanced adsorbent for quaternary ammonium alkaloids

A novel π-conjugated polymer-modified magnetic dendritic fibrous mesoporous silica adsorbent (MB@KCC-1@π-CP) is reported for the accurate determination of quaternary ammonium alkaloids (QAAs) in complex body fluid matrices. It is demonstrated that the magnetic dendritic fibrous mesoporous silica (MB@KCC-1) is an excellent carrier combining magnetism, high specific surface area, unique hierarchical pore structure, and fast mass transfer rate. The π-conjugated polymer (π-CP) can efficiently retain QAAs (berberine, coptisine, palmatine, jatrorrhizine) by multiple interactions. In addition, the adsorption kinetics and adsorption mechanism were also studied and discussed. Under optimized extraction conditions, MB@KCC-1@π-CP-based magnetic solid-phase extraction (MSPE) and high-performance liquid chromatography (HPLC) method affords a wide linear range (0.5-20000 ng mL-1), low limits of detection (0.2-2 ng mL-1), and satisfactory relative standard deviations (RSD) of inter-day (< 2.4%) and intra-day (< 3.1%) for QAAs. Trace QAAs in complex human blood plasma samples were successfully detected by the established method.

Adsorption Ability of Graphene Aerogel and Reduced Graphene Aerogel toward 2,4-D Herbicide and Salicylic Acid

Within this work, new aerogels based on graphene oxide are proposed to adsorb salicylic acid (SA) and herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous media. Graphene oxide aerogel (GOA) and reduced graphene oxide aerogel (rGOA) were obtained by freeze-drying processes and then studied by Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The influence of contact time and the concentration of the adsorbates were also assessed. It was found that equilibrium for high adsorption is reached in 150 min. In a single system, the pseudo-first-order, pseudo-second-order kinetic models, Intraparticle diffusion, and Elovich models were used to discuss the detail of the aerogel adsorbing pollutant. Moreover, the Langmuir, Freundlich, and Temkin adsorption models were applied to describe the equilibrium isotherms and calculate the isotherm constants.