The metal-organic coordination polymers at the nanoscale have emerged as attractive nanomaterials due to their tunable nature. In this work, we for the first time prepared an adenine-based lanthanide coordination polymer nanoparticle (CPNP) with fluorescence sensing function. This kind of CPNP was composed of adenine, terbium ion (Tb(3+)), and dipicolinic acid (DPA) as an auxiliary linking molecule that can sensitize the fluorescence of Tb(3+). The fluorescence of the CPNPs is very weak due to the existence of photoinduced electron transfer (PET) from adenine to DPA, which prevents the intramolecular energy transfer from DPA to Tb(3+), leading to the quench of fluorescence of the CPNPs. In the presence of Hg(2+), however, significant enhancement in the fluorescence of CPNPs was observed because of the suppression of the PET process by the coordination of Hg(2+) with adenine. As a kind of Hg(2+) nanosensor, the CPNPs exhibit excellent selectivity and ultrahigh sensitivity up to the 0.2 nM detection limit. The CPNPs also possess an approximately millisecond-scale-long fluorescence lifetime due to the inclusion of Tb(3+) ions. We envision that the CPNPs could find great potential applications in ultrasensitive time-resolved fluorometric assays and biomedical imaging in the future owing to their long emission lifetimes, excellent dispersion, and stability in aqueous solution.
In nature, individual cells contain multiple isolated compartments in which cascade enzymatic reactions occur to form essential biological products with high efficiency. Here, we report a cell-inspired design of functional hydrogel particles with multiple compartments, in which different enzymes are spatially immobilized in distinct domains that enable engineered, one-pot, tandem reactions. The dense packing of different compartments in the hydrogel particle enables effective transportation of reactants to ensure that the products are generated with high efficiency. To demonstrate the advantages of micro-environmental modifications, we employ the copolymerization of acrylic acid, which leads to the formation of heterogeneous multi-compartmental hydrogel particles with different pH microenvironments. Upon the positional assembly of glucose oxidase and magnetic nanoparticles, these hydrogel particles are able to process a glucose-triggered, incompatible, multistep tandem reaction in one pot. Furthermore, based on the high cytotoxicity of hydroxyl radicals, a glucose-powered therapeutic strategy to kill cancer cells was approached.
A three-dimensional (3D) macroporous carbon (3D-KSCs) derived from kenaf stem (KS) is proposed as a novel supporting material for electrochemical sensing and a biosensing platform. A series of 3D-KSCs/inorganic nanocomposites such as Prussian blue (PB) nanoparticles (NPs)-carboxylic group-functionalized 3D-KSCs (PBNPs-3D-FKSCs), CuNiNPs-3D-KSCs, and CoNPs-3D-KSCs were prepared by a facile two-step route consisting of carbonization and subsequent chemical synthesis or one-step carbonization of KS-metal ion complex. The obtained 3D-KSCs/inorganic nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier transform-infrared spectroscopy. A whole piece of 3D-KSCs/nanocomposites was used to prepare an integrated 3D-KSCs/nanocomposite electrode. Compared to the electrode modified by graphene, carbon nanotubes and their derivatives, which can form close-packed structure after assembled on electrode surface, the integrated 3D-KSCs/nanocomposite electrode shows a 3D honeycomb porous structure. Such structure provides a large specific surface area, effectively supports a large number of electro-active species, and greatly enhances the mass and electron transfer. The electrochemical behaviors and electrocatalytic performances of the integrated 3D-KSCs/inorganic nanocomposite electrode were evaluated by cyclic voltammetry and the amperometric method. The resulted PBNPs-3D-FKSCs, CuNiNPs-3D-KSCs, and CoNPs-3D-KSCs electrode show good electrocatalytic performances toward the reduction of H2O2, the oxidation of glucose and amino acid, respectively. Therefore, the low-cost, renewable, and environmentally friendly 3D-KSCs should be promising supporting materials for an electrochemical sensor and biosensor.
Metal-organic frameworks (MOFs) have emerged as very fascinating functional materials due to their diversity nature. A nanocomposite consisting of copper nanoparticles dispersed within a carbon matrix (Cu NPs@C) is prepared through a one-pot thermolysis of copper-based metal-organic framework precursors. Cu NPs@C can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to form a colored product in the presence of H2 O2 . As a peroxidase mimic, Cu NPs@C not only has the advantages of low cost, high stability, and easy preparation, but also follows Michaelis-Menten behaviors and shows strong affinity to H2 O2 . As the Cu NPs' surfaces are free from stabilizing agent, Cu NPs@C exhibited a higher affinity to H2 O2 than horseradish peroxidase. On the basis of the inhibitory effect of ascorbic acid (AA) on oxidation of TMB, this system serves as a colorimetric method for the detection of AA, suggesting that the present work would expand the potential applications of MOF-derived nanocomposites in biomedical fields.
Amorphous CeOx-doped Rh-Ni NPs grown on reduced graphene oxide nanosheets have been used as highly efficient and recyclable catalysts for complete hydrogen generation from aqueous solution of N2H4BH3 or N2H4.
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