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J Nanosci Nanotechnol ; 19(11): 7229-7235, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31039880


A single step fast track method is proposed to determine melamine based on strong hydrogen bonding between exocyclic amine group in melamine moiety and hydroxyl group of tannic acid (TA); acting as reducing and functionalizing agent for synthesis of gold nanoparticles (Au NPs). The proposed strategy is facile and highly time saving; as the detection of melamine with labelfree gold nanoparticles was accomplished within five minutes. The colorimetric probe exhibits high detection limit of 8 nM for melamine determination in raw milk, which is very low as compared to other capping ligands employed for Au NPs such as borohydride, citrate and 3,5-dihydroxybenzoic acid. The results show a highly sensitive linear range (0.03-2.5 µM) between absorption ratio and concentration of melamine with a correlation coefficient of 0.991. Proposed methodology is proven effective for on-site screening without using costly instrumentation.

Artigo em Inglês | MEDLINE | ID: mdl-30077892


Rapid, reliable, onsite approaches for detection trace level of trinitrotoluene (TNT) is a pressing necessity for both homeland security and environmental protection. To this end, hydrophilic amine(-NH2) protected Au@Ag nanoparticles (NPs) were developed and fabricated as colorimetric paper sensor for delicate detection of TNT. The as-developed nanoprobe selectively reacts with TNT through classic Meisenheimer complex formation by means of charge transfer process from an electron-rich NH2 group of ß-cysteamine to an electron-deficient nitro group on TNT. Due to the absence of this particular interaction of other nitroaromatics, the proposed probe is highly selective for TNT detection with a better linear range (0-20 µg/mL) and limit of detection (LOD) of 0.35 µg/mL. The present work provides a novel and facile strategy to fabricate colorimetric paper sensors with rapid and selective recognition ability for label free analysis of TNT.

Chem Commun (Camb) ; 54(70): 9853-9856, 2018 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-30112535


We successfully fabricated 19F magnetic resonance imaging (MRI) nanoprobes by partly replacing the 2-methylimidazolate of the metal organic framework (MOF) matrix ZIF-8, of which the strong 19F MRI signal displays an interesting pH dependence property, indicating its great potential as a 19F MRI contrast agent for stimuli-responsive imaging with high penetration depth and low background.

Nanoscale ; 10(12): 5658-5666, 2018 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-29528345


A hierarchical excavated iron-nitrogen codoped mesoporous carbon (Ex-FeN-MC) electrocatalyst has been successfully synthesized by pyrolysis of the unique ureidopyrimidinone containing organic precursor MAMIS by using silica as the mesoporous template and iron nitrate as the source of iron. The selected organic precursor has multifunctionalities with diverse distribution of nitrogen and oxygen species which constitute interesting features to prepare the Ex-FeN-MC electrocatalyst. The as-prepared Ex-FeN-MC material shows unexpectedly higher catalytic activities towards ORR/OER performances with an overpotential of 250 mV for OER in alkaline solution at a current density of 10 mA cm-2, while the ORR activity is almost similar to that of commercial Pt/C. It is believed that the excellent electrochemical performance results from the synergic contribution of the hierarchical uniform mesoporous structure, evenly distributed iron nanoparticles and high density of Ex-FeN-MC catalytically active sites. The presence of the hierarchical uniform mesoporous structure considerably accelerates the mass transfer and efficiently promotes the full utilization of active sites. Furthermore, it also possesses amorphous carbon in coexistence with lattice graphitic carbon which also enhanced the ORR/OER performances. Our research findings can surely provide a new insight to design highly active ORR/OER electrocatalysts by utilizing more novel organic precursors to provide interesting characteristics to electrocatalysts, as well as open up a route for constructing unique multifunctional materials with mesoporous architectures for electrocatalysis and supercapacitor applications.