An Ethyl-Thioglycolate-Functionalized Fe3O4@ZnS Magnetic Fluorescent Nanoprobe for the Detection of Ag+ and Its Applications in Real Water Solutions

Ethyl-thioglycolate-modified Fe₃O₄@ZnS nanoparticles (Fe₃O₄@ZnS-SH) were successfully prepared using a simple chemical precipitation method. The introduction of ethyl thioglycolate better regulated the surface distribution of ZnS, which can act as a recognition group and can cause a considerable quenching of the fluorescence intensity of the magnetic fluorescent nanoprobe, Fe₃O₄@ZnS-SH. Benefiting from stable fluorescence emission, the magnetic fluorescent nanoprobe showed a highly selective fluorescent response to Ag+ in the range of 0-400 μM, with a low detection limit of 0.20 μM. The magnetic fluorescent nanoprobe was used to determine the content of Ag⁺ in real samples. A simple and environmentally friendly approach was proposed to simultaneously achieve the enrichment, detection, and separation of Ag⁺ and the magnetic fluorescent nanoprobe from an aqueous solution. These results may lead to a wider range of application prospects of Fe₃O₄ nanomaterials as base materials for fluorescence detection in the environment.

Freestanding 3D-interconnected carbon nanofibers as high-performance transducers in miniaturized electrochemical sensors

3D-carbon nanomaterials have proven to be high-performance transducers in electrochemical sensors but their integration into miniaturized devices is challenging. Herein, we develop printable freestanding laser-induced carbon nanofibers (f-LCNFs) with outstanding analytical performance that furthermore can easily allow such miniaturization through a paper-based microfluidic strategy. The f-LCNF electrodes were generated from electrospun polyimide nanofibers and one-step laser carbonization. A three-electrode system made of f-LCNFs exhibited a limit of detection (LOD) as low as 1 nM (S/N = 8) for anodic stripping analysis of silver ions, exhibiting the peak at ca. 100 mV vs f-LCNFs RE, without the need of stirring. The as-described system was implemented in miniaturized devices via wax-based printing, in which their electroanalytical performance was characterized for both outer- and inner-sphere redox markers and then applied to the detection of dopamine (the peak appeared at ca. 200 mV vs f-LCNFs RE) with a remarkable LOD of 55 pM. When modified with Nafion, the f-LCNFs were highly selective to dopamine even against high concentrations of uric and ascorbic acids. Especially the integration into closed microfluidic systems highlights the strength 3D porous structures provides excellent analytical performance paving the way for their translation to affordable lab-on-a-chip devices where mass-production capability, unsophisticated fabrication techniques, transfer-free, and customized electrode designs can be realized.

Crystalline carbon modified hierarchical porous iron and nitrogen co-doped carbon for efficient electrocatalytic oxygen reduction

Hierarchical porous iron and nitrogen co-doped carbon (Fe-N/C) materials have been considered as an appealing non-noble metal-based catalyst in oxygen reduction reactions (ORR). However, the conductivity loss caused by the scattering of electrons on pores and defects markedly limits their catalytic activity, which attracted seldom attention in this area. Herein, a novel crystalline carbon modified hierarchical porous Fe-N/C electrocatalyst with enhanced electronic conductivity is designed and prepared via a two-step calcination-catalysis process. The resistivity of hierarchical porous Fe-N/C is decreased from 2.123 Ω cm to 0.479 Ω cm after crystalline carbon introduction. The electrocatalyst annealed at 800 °C (Fe-N/C-800) exhibits a superior activity with the half-wave potential (E_1/2) of 0.89 V, which outperforms the commercial carbon-supported platinum (Pt/C) catalyst (0.85 V). The strategy of crystalline carbon modification provides a fresh approach to improve the electronic conductivity of porous carbon-based materials.

The functionalization of gold nanoparticles as a novel platform for the highly efficient electrochemical detection of silver ions

A novel platform was constructed by the functionalization of gold nanoparticles for the highly efficient electrochemical detection of silver ions.

Heteroatom-doped graphene as sensing materials: a mini review

Graphene is one of the astounding recent advancements in current science and one of the most encouraging materials for application in cutting-edge electronic gadgets. Graphene and its derivatives like graphene oxide and reduced graphene oxide have emerged as significant nanomaterials in the area of sensors. Furthermore, doping of graphene and its derivatives with heteroatoms (B, N, P, S, I, Br, Cl and F) alters their electronic and chemical properties which are best suited for the construction of economical sensors of practical utility. This review recapitulates the developments in graphene materials as emerging electrochemical, ultrasensitive explosive, gas, glucose and biological sensors for various molecules with greater sensitivity, selectivity and a low limit of detection. Apart from the most important turn of events, the properties and incipient utilization of the ever evolving family of heteroatom-doped graphene are also discussed. This review article encompasses a wide range of heteroatom-doped graphene materials as sensors for the detection of NH₃, NO₂, H₂O₂, heavy metal ions, dopamine, bleomycinsulphate, acetaminophen, caffeic acid, chloramphenicol and trinitrotoluene. In addition, heteroatom-doped graphene materials were also explored for sensitivity and selectivity with respect to interfering analytes present in the system. Finally, the review article concludes with future perspectives for the advancement of heteroatom-doped graphene materials.

Graphene is one of the astounding recent advancements in current science and one of the most encouraging materials for application in cutting-edge electronic gadgets.

Multifunctional Binding Chemistry on Modified Graphene Composite for Selective and Highly Efficient Adsorption of Mercury

Engineering of multifunctional binding chemistry on graphene composites using thiol-ene click reaction for selective and highly efficient adsorption of mercury(II) is demonstrated. Graphene oxide (GO) is used as an initial material for covalent attachment of cysteamine molecules by thiol-ene click reaction on C═C groups to achieve a partially reduced graphene surface with multiple binding chemistry such as O, S, and N. Batch adsorption studies showed remarkable adsorption rate with only 1 mg L^-1 dosage of adsorbent used to remove 95% Hg (II) (∼1.5 mg L^-1) within 90 min. The high adsorption capacity of 169 ± 19 mg g^-1, high selectivity toward Hg in the presence of 30 times higher concentration of competing ions (Cd, Cu, Pb) and high regeneration ability (>97%) for five consecutive adsorption-desorption cycles were achieved. Comparative study with commercial activated carbon using spiked Hg (II) river water confirmed the high performance and potential of this adsorbent for real mercury remediation of environmental and drinking waters.