The Controllable Synthesis Of Two Dimensional Nanomaterials And Their Application In Energy Electrocatalysis And Sensors

The unique structure and excellent optical,acoustic,electrical,magnetic and thermal properties of two-dimensional(2D)nanomaterials make them promising in energy catalysis,sensors and biomedicine.Herein,we choose several typical 2D nanomaterials and focus on the regulation of their compositions and structures by changing the synthesis strategy to obtain functional materials with excellent performances.These 2D nanomaterials were applied to the fuel cell,oxygen evolution reaction in water splitting and biological sensing.The relationships between compositions,structures and performances were also explored to provide theoretical guidance for the design of two dimensional nanomaterials.1.In view of the scarcity and expensive price of metal Pt,Pd is introduced to develop binary Pt based catalysts for fuel cells,due to its relatively low cost,high lattice compatibility with Pt and good catalytic activity.Herein,we propose a facile seed-mediated growth approach for synthesis of Pt-on-Pd bimetallic dendritic nanosheets(DNSs)through the growth of Pt branches on ultrathin 2D Pd nanosheets(NSs).By regulating the molar ratios of Pt precursor K2 Pt Cl4 to Pd nanosheets seeds,the Pd-Pt DNSs with different densities of Pt branches supported on Pd nanosheets can be obtained.The larger the molar ratios,the densier the Pt branches.These as-prepared bimetallic catalysts show improved catalytic activities to oxygen reduction reaction(ORR)and methanol oxidation reaction(MOR).The ORR mass activity of the best nanocrystals was 2.2 times higher,and MOR mass activity was 3.4 times higher than commercial Pt/C catalysts.In addition,these spatially-separated Pt branches supported on 2D nanosheets also endow Pd-Pt DNSs with impressive durability in ORR,with losses of only 5.4% in specific activity and 18.9% in mass activity,while the losses of Pt/C catalysts were 28.0% and 50.0%,respectively,after 10,000-cycle accelerated durability tests.This two-dimensional dendritic nanosheet structure can be extended to other 2D metal nanosheet substrates for the synthesis of platinum-based electrocatalysts with excellent catalytic performances.2.Due to high overpotential,high cost and low energy conversion efficiency of oxygen evolution reduction in Water splitting,it is an urgency to develop efficient and cheap nonnoble metal nano-catalysts for OER.Herein,we propose a top-down strategy for preparation of amorphous binary and ternary Fe Co Ni hydr(oxy)oxides.The metal salt precursors are firstly reduced by sodium borohydride to form zero-valent metal block materials,and then they are etched into metallic nanomaterials with specific morphology in alkaline solutions by glutathione owning to its coordination with metals.By regulating glutathione ligand concentration,p H value and reaction time,flower-like Fe nanosheets was obtained.The amorphous binary Fe Co,Fe Ni and ternary Fe Co Ni metallic hydr(oxy)oxides are prepared by adding Co,Ni or Co and Ni precursors into Fe precursor solutions.For binary and ternary nanomaterials,the contents of doped metal components have great effects on their morphology with nanosheet-like structure at low doping amounts while most hammer-like structures at high doping amounts.Subsequently,the catalytic activities of thes hydr(oxy)oxides towards OER were investigated in alkaline solutions.It is found that binary and ternary catalysts have significant enhanced OER catalytic performances compared with undoped catalysts,and the component contents of the same series doped catalysts play a decisive role in the catalytic activities.The study on the property regulation of metal hydr(oxy)oxide catalysts provide certain significance for the development of non-noble metal catalysts for OER in water splitting.3.MXenes as a typical class of layered two-dimensional materials have recently been widely applied in energy storage,electrocatalysis,sensors,adsorption,water purification,and so on,due to their tunable versatile properties.Nevertheless,their applications in sensing fields are limited by their thickness.Ultrathin MXenes nanosheets with large specific surface area and facile surface functionalization are more popular choices for sensing platforms.Same as other graphene-like two-dimensional nanomaterials,thin MXenes nanosheets do not possess the capability of fluorescence emission itself,but show strong fluorescence quenching ability.Herein,we developed an “off-on” fluorescence sensor based on Ti3C2 MXene nanosheets for detection of human papillomavirus DNA.Ti3C2 nanosheets as a fluorescence quenching platform possess different affinities with FAM-labeled single stranded DNA probe(ss DNA)and double stranded DNA(ds DNA).Combined with the signal amplification of exonuclease III,a rapid and sensitive detection of DNA is acheived.We investigate the fluorescence quenching amouts,quenching time of Ti3C2 toward ss DNA probe and ds DNA and the anti-interference ability and selectivity for the target detection.Under optimal conditions,the determination of HPV-18 DNA has a linear range of 0.5 to 50 n M with a very low detection limit of 100 p M.This magnified fluorescent sensor is also applied in actual samples of cervical cancer patient for HPV 18 analysis.This study indicates Ti3C2 nanosheets as promising two-dimensional materials quite suitable for building excellent fluorescence DNA biosensors.