Preparation Of Functional Carbon And Noble Metal Nanomaterials And Their Applications For Electrocatalysis And Sensing

Nanomaterials are widely used in basic research and applied research fields with the interdisciplinary penetration and the development of nanotechnology.In particular,functionalized nanomaterials have brought new vitality to the fields of materials,chemistry,physics,biology,and medicine.In this respect,the carbon and noble metal nanomaterials show great potential application value.At the same time,the macrocyclic supermolecule is always the research basis and important component of supramolecular chemistry.This thesis mainly centered on the noble metal and carbon nanomaterials.By combining the merits of noble metal/carbon nanomaterials and macrocyclic supermolecule,a series of hybrid nanomaterials with multiple components and multiple advantages are constructed.The optical,electrical,thermal,and catalytic properties of the noble metal/carbon nanomaterials are fully integrated with the host-guest recognition properties of the macrocyclic supermolecule.The water-soluble macrocyclic supermolecules could be grafted on the surface of carbon nanomaterials through covalent?Au-S?or non-covalent interactions?hydrogen-bond interactions,?-?interactions,electrostatic interaction,and hydrophobic interactions?.This enriches the variety of nanomaterials,and also enhances and extends the application of nanomaterials in many fields,such as electrocatalysis and electrochemical sensing.In addition,we also look at the preparation of new carbon quantum dot nanomaterials and explore their potential applications in the field of electrochemical/fluorescence sensing.The main research contents are as follows:1.?1?We reported a water phase method for preparation of?-cyclodextrin??-CD?functionalized reduced graphene oxide??-CD@RGO?for loading ultrasmall?2.0 nm?Pd-Pt bimetallic alloy electrocatalyst.The?-CD functionalization can significantly increase the interaction between metal precursors(PtCl₆^2-,Pd²⁺)and the RGO support,which was caused by the large number of hydroxyl groups.This can prevent the aggregation and overgrowth of nanocrystals.This method can realize the in-situ synthesis of Pt and Pd nanoparticles.The process was carried out at room temperature within 30 min and without the need of any organic solvent.The integration of?-CD and RGO was responsible for the formation of the monodispersed 2.0 nm Pd–Pt bimetallic nanoclusters.Inspired by the monodisperse,ultrasmall,and pristine properties of the Pd–Pt clusters,the Pd–Pt@?-CD-RGO nanohybrid displayed enhanced activity for methanol and ethanol oxidation in alkaline media in comparison with the commercial Pd/C catalysts.The enhanced electrocatalytic activity of the Pd-Pt@?-CD-RGO could be attributed to three main factors:?a?the Pd-Pt clusters with very small size?2.0 nm?would offer more accessibility to methanol or ethanol oxidation,thus remarkably improving the atomic utilization efficiency;?b?the excellent monodispersity and uniformity of Pd-Pt loaded on?-CD-RGO with high surface area might be favorable for improving the catalytic performance;?c?the formation of bimetallic surface atom arrangement,and/or the synergistic effect originating from the coexistence of surface Pd and Pt atoms should also be emphasized.?2?The development of non-Pt precious metal nanomaterials can effectively reduce the cost of the catalyst.Non-Pt noble metal clusters like Pd clusters are considered to be promising electrocatalysts for fuel cells,but they still suffer problems such as easy occurrence of aggregation during the catalysis reactions.Therefore,it is necessary to enhance the stability of the material.To solve these problems,we demonstrate a water-based method for in-situ synthesis of ultrasmall Pd clusters with an average size of 2.5 nm uniformly supported on single-walled carbon nanohorns functionalizedbypara-sulfonatedcalix[8]arene?SCX₈-SWCNHs?.The SCX₈-SWCNHs composite nanomaterials have many negatively charged-SO^3-at the end of SCX₈,which has a strong electrostatic interaction with the positively charged Pd²⁺precursors.Highly-dispersed electrocatalyst could be obtained by using this method and the size of the Pd nanoclusters is 2.5 nm.These reactions were carried out at room temperature without the need for organic solvent.The Pd@SCX₈-SWCNHs nanohybrid displayed enhanced activity for ethylene glycol and glycerol electrooxidation in alkaline media in comparison with the commercial Pd/C catalyst.The enhanced electrocatalytic activity of the Pd@SCX₈-SWCNHs could be attributed to two main factors:?a?the Pd nanoclusters with very small size?2.5 nm?would offer more accessibility to ethylene glycol and glycerol electrooxidation for catalytic oxidation,thus remarkably improving the atomic utilization efficiency;?b?the excellent monodispersity and uniformity of Pd loaded on SCX₈-SWCNHs with high surface area might be favorable for improving the catalytic performance.?3?We reported a surfactant-controlled method for the synthesis of Pd-Pt bimetallic nanocrystals?NCs?with different morphology through a high-yield and one-pot synthesis in aqueous solution.Polyallylamine hydrochloride?PAH?was used to mediate the sequential reduction kinetics.By simply varying the concentration of PAH in the growth solution,three different shaped Pd-Pt NCs?nanospheroids,nanoflowers,nanoworms?were prepared by using H₂PtCl₆ and PdCl₂ as metal precursors and CTAB as stabilizer in the presence of PAH as surface controller.Compared with the nanoworms and nanospheroids,the nanoflowers perform Pd-Pt core-shell structures and have a higher electrocatalytic activity.Important role of PAH was certified to tune the reduction kinetics and therefore determine the final morphologies of Pd-Pt NCs.Best of our knowledge,it's the first time that Pd-Pt NCs with PAH-controlled structures prepared by altering the sequential reduction kinetics at one-pot aqueous solution.Furthermore,these Pd-Pt NCs have shown enhanced electrocatalytic activities towards ethanol oxidation compared to commercial Pd/C catalyst.2.?1?The?-CD was grafted on the surface of PTCA functionalized SWCNHs via the coordination of Au-S.A highly sensitive electrochemical sensing platform was constructed based on the?-CD–Au@PTCA–SWCNHs composite.Due to the synergistic effects from the SWCNHs?e.g.the good electrochemical properties and large surface area?and?-CD?e.g.a hydrophilic external surface and a high supramolecular recognition and enrichment capability?,the?-CD–Au@PTCA–SWCNHs modified glass carbon electrode was found to have a linear response range of 0.01–10.00?M both for myricetin and rutin with relatively low detection limits of0.0038?M for myricetin and 0.0044?M for rutin,implying that?-CD–Au@PTCA–SWCNHs nanohybrids are excellent sensing materials for the electrochemical determination of myricetin and rutin.In addition,molecular docking was used to study the interaction of the host/guest inclusion complex,and the inclusion mode was also obtained.?2?In this work,ultrafine Pd clusters with a uniform size of².0 nm were monodispersed on the surface of RGO using a clean and green approach in the absence of additional reductants and surfactants.Disulfide linked?-cyclodextrin dimer?SS-?-CD?was non-covalently bonded to the surface of Pd@RGO.By combining the merits of Pd@RGO and the SS-?-CD,a highly sensitive electrochemical sensing platform was developed based on the SS-?-CD-Pd@RGO nanohybrids.Electrochemical simultaneous detection of baicalin and luteolin using SS-?-CD-Pd@RGO nanohybrids-modified electrode is described for the first time.The SS-?-CD showed higher supramolecular recognition capability than the native?-CD,which may be caused by the cooperative binding abilities of two adjacent CD units.Due to the synergistic effects from the Pd@RGO?e.g.the good electrochemical properties and large surface area?and SS-?-CD?e.g.a hydrophilic external surface,a high supramolecular recognition,and a good enrichment capability?,the SS-?-CD-Pd@RGO modified electrode was found to have linear response ranges of0.02–20.00?M for baicalin and 0.01–10.00?M for luteolin with relatively low detection limits of 0.0052?M for baicalin and 0.0070?M for luteolin,respectively.The results indicated that SS-?-CD-Pd@RGO nanohybrids are excellent sensing materials for the electrochemical determination of flavonoids.The proposed method could be successfully utilized to detect baicalin and luteolin in serum samples,and exhibited a promising application in practice.3.?1?By combining the merits of water-soluble pillar[6]arenes?WP6s?and nitrogen-doped carbon quantum dots?N-CQDs?,a sensitive electrochemical sensing platform was constructed by using the WP6-N-CQD nanocomposites as an electrode material for the detection of trinitrotoluene?TNT?.N-CQDs were prepared via microwave route by using urea and citric acid as raw materials.Two kinds of macrocyclic hosts,?-CD and WP6,were incorporated onto the N-CQDs via hydrogen bonding and?-?interactions,respectively.The FTIR,TGA,and XPS characterizitions demonstrated that the?-CD-N-CQD and WP6-N-CQD composites were successfully prepared.The WP6-N-CQD-modified glass carbon electrode indicated an enhanced electrochemical signal than the?-CD-N-CQDs/GCE in the reduction of2,4,6-trinitrotoluene?TNT?,which was attributed to the higher supramolecular recognition capability of the WP6 host than that of?-CD towards TNT.The linear ranges of 0.001?M-1.0?M and 1.0?M-20.0?M were obtained by using this electrochemical sensing platform.The detection limit was 0.95 nM?S/N=3?.The developed electrochemical sensing technique was successfully applied for the detection of TNT in lake water samples.Therefore,WP6-N-CQD nanocomposites are promising for the construction of high performance electrochemical sensors for the detection of explosives.Molecular docking was used to study the interaction of the host/guest inclusion complex,and the inclusion mode was also obtained.?2?Monitoring of nitroaromatic explosives plays a vital role in homeland security and public safety.In this work,a facile,economical,and one-step hydrothermal route is used to synthesize photoluminescent N-C-dots by employing allylamine as both the carbon and nitrogen source for the first time.The average size of the synthesized N-C-dots is 2.88±0.4 nm.The N-C-dots show strong blue fluorescence and exhibit a high fluorescence quantum yield of 15%.The N-C-dots were thoroughly characterized using various techniques,which exhibited excellent solubility and strong fluorescence.The N-C-dots can be used as a fluorescent probe for the detection of TNP with a high selectivity.The excellent quenching performance of TNP towards N-C-dots was ascribed to the synergistic effect of electron transfer,fluorescence resonance energy transfer and the hydrogen-bond interactions between N-C-dots and TNP.Furthermore,the synthesized bright N-C-dots can be applied as a new type of fluorescent ink without any chemical modification.Besides,a detailed mechanism for the formation of N-C-dots via self-polymerization and carbonization was proposed.