Metal nanoparticle decorated carbon nanotubes and methods of preparation and use

1. A method of forming carbon nanotubes decorated with nanoparticles, the method comprising:

mixing a metal precursor with a plurality of carbon nanotubes to form a metal precursor-carbon nanotubes mixture; and

exposing the metal precursor-carbon nanotubes mixture to electromagnetic radiation to deposit the metal precursor as the nanoparticles on a major surface of the carbon nanotubes, wherein the nanoparticles comprise a metal alloy nanoparticle, and one or more of a metal nanoparticle and a metal oxide nanoparticle.

2. The method of claim 1 , wherein mixing the metal precursor with the plurality of carbon nanotubes comprises mixing the carbon nanotubes with the metal precursor selected from the group consisting of silver acetate (CH 3 COOAg), silver chloride (AgCl), silver nitrate (AgNO 3 ), chloroauric acid (HAuCl 4 ), hexachloroplatinic acid (H 2 PtCl 6 .(H 2 O) 6 ), palladium chloride (PdCl 2 ), nickel acetate tetrahydrate (Ni(CH 3 COO) 2 .4H 2 O), nickel chloride (NiCl 2 ), zinc acetate dihydrate (Zn(O 2 CCH 3 ) 2 .2H 2 O), zinc nitrate (Zn(NO 3 ) 2 ), cobalt nitrate hexahydrate (Co(NO 3 ) 2 .6H 2 O), cobalt chloride (CoCl 2 ), and combinations thereof.

3. The method of claim 1 , wherein exposing comprises exposing the metal precursor-carbon nanotubes mixture to electromagnetic radiation to deposit the metal precursor as nanoparticles, wherein the nanoparticles are selected from the group consisting of platinum (Pt), palladium (Pd), silver (Ag), gold (Au), nickel (Ni), titanium (Ti), tin (Sn), ruthenium (Ru), zinc (Zn), copper (Cu), zinc oxide (ZnO), nickel oxide (NiO), copper oxide (CuO), iron oxide (Fe 3 O 4 ), cobalt oxide (CoO 3 ), titanium oxide (TiO 2 ), cerium oxide (CeO 2 ), manganese dioxide (MnO 2 ), platinum cobalt alloy (Pt 3 Co), platinum nickel alloy (Pt 3 Ni), palladium cobalt alloy (Pd 3 Co), palladium iron alloy (Pd 3 Fe), platinum iron alloy (Pt 3 Fe), and combinations thereof.

4. The method of claim 1 , wherein exposing the metal precursor-carbon nanotubes mixture to electromagnetic radiation comprises exposing the metal precursor-carbon nanotubes mixture to solar radiation.

5. A nanoparticle decorated carbon nanotubes formed by exposing a mixture of a metal precursor and a plurality of carbon nanotubes to electromagnetic radiation to deposit the metal precursor as nanoparticles on a major surface of the plurality of carbon nanotubes, wherein the nanoparticles comprise a metal alloy nanoparticle, and one or more of a metal nanoparticle and a metal oxide nanoparticle.

6. The nanoparticle decorated carbon nanotubes of claim 5 , wherein the metal precursor comprises silver acetate (CH 3 COOAg), silver chloride (AgCl), silver nitrate (AgNO 3 ), chloroauric acid (HAuCl 4 ), hexachloroplatinic acid (H 2 PtCl 6 .(H 2 O) 6 ), palladium chloride (PdCl 2 ), nickel acetate tetrahydrate (Ni(CH 3 COO) 2 .4H 2 O), nickel chloride (NiCl 2 ), zinc acetate dihydrate (Zn(O 2 CCH 3 ) 2 .2H 2 O), zinc nitrate (Zn(NO 3 ) 2 ), cobalt nitrate hexahydrate (Co(NO 3 ) 2 . 6H 2 O), cobalt chloride (CoCl 2 ), or combinations thereof.

7. The nanoparticle decorated carbon nanotubes of claim 5 , wherein the nanoparticles comprise platinum (Pt), palladium (Pd), silver (Ag), gold (Au), nickel (Ni), titanium (Ti), tin (Sn), ruthenium (Ru), zinc (Zn), copper (Cu), zinc oxide (ZnO), nickel oxide (NiO), copper oxide (CuO), iron oxide (Fe 3 O 4 ), cobalt oxide (CoO 3 ), titanium oxide (TiO 2 ), cerium oxide (CeO 2 ), manganese dioxide (MnO 2 ), platinum cobalt alloy (Pt 3 Co), platinum nickel alloy (Pt 3 Ni), palladium cobalt alloy (Pd 3 Co), palladium iron alloy (Pd 3 Fe), platinum iron alloy (Pt 3 Fe), or combinations thereof.

8. The nanoparticle decorated carbon nanotubes of claim 5 , wherein the nanotube comprises a plurality of carbon nanotubes comprising single-walled carbon nanotubes, multi-walled carbon nanotubes, or combinations thereof.

9. The nanoparticle decorated carbon nanotubes of claim 5 , wherein a size of the nanoparticles is about 2 nanometers (nm) to about 50 nm.

10. A method of forming a nanoparticle decorated carbon nanotubes-graphene composite, the method comprising:

mixing a metal precursor with graphite oxide and a plurality of carbon nanotubes to form a mixture; and

exposing the mixture to solar radiation to reduce graphite oxide to graphene and to form a carbon nanotubes-graphene composite and to concurrently reduce the metal precursor to nanoparticles, and to deposit the nanoparticles on a major surface of the carbon nanotubes-graphene composite, wherein the nanoparticles comprise a metal alloy nanoparticle, and one or more of a metal nanoparticle and a metal oxide nanoparticle.

11. The method of claim 10 , wherein the mixing comprises mixing the graphite oxide and the plurality of carbon nanotubes with the metal precursor selected from the group consisting of zinc acetate (Zn(O 2 CCH 3 ) 2 ), zinc chloride (ZnCl 2 ), and combinations thereof.

12. The method of claim 10 , wherein the mixing comprises mixing the graphite oxide and the metal precursor with a plurality of multi-walled carbon nanotubes.

13. A sensor comprising:

a composite material comprising carbon nanotubes and graphene; and

nanoparticles deposited on a major surface of the carbon nanotubes of the composite material, wherein the nanoparticles comprise a metal alloy nanoparticle, and one or more of a metal nanoparticle and a metal oxide nanoparticle.

14. The sensor of claim 13 , wherein the nanoparticles are deposited by exposing a mixture of a metal precursor, graphite oxide and a plurality of carbon nanotubes to electromagnetic radiation.

15. The sensor of claim 14 , wherein the electromagnetic radiation comprises solar radiation.

16. The sensor of claim 13 , wherein the sensor is configured to detect an organophosphorus compound in a medium, and wherein the organophosphorus compound is present in a concentration range of about 1 nanomolar (nM) to about 1 picomolar (pM).

17. The sensor of claim 16 , wherein the organophosphorus compound comprises paraoxon, parathion, carbaryl, malathion, or combinations thereof.

18. The sensor of claim 13 , wherein a size of the nanoparticle is about 10 nm to about 60 nm.

19. The sensor of claim 13 , wherein an active surface area of the sensor is about 30 mm 2 .

20. A method for detecting an organophosphorus compound in a medium, the method comprising:

contacting a sensor with the medium, wherein the sensor comprises a composite material comprising carbon nanotubes and graphene, and wherein a plurality of nanoparticles are deposited on a major surface of the carbon nanotubes, wherein the nanoparticles comprise a metal alloy nanoparticle, and one or more of a metal nanoparticle and a metal oxide nanoparticle; and

sensing an inhibition current by the sensor to detect the presence and a concentration of the organophosphorus compound in the medium.

21. The method of claim 20 , wherein depositing the plurality of nanoparticles is by exposing a mixture of a zinc metal precursor, graphite oxide and a plurality of carbon nanotubes to electromagnetic radiation.

22. The method of claim 20 , wherein the sensing comprises sensing the inhibition current by the sensor to detect the presence and the concentration of paraoxon, parathion, carbaryl, malathion or combinations thereof, in a concentration range of about 1 nM to about 1 pM.

23. The method of claim 20 , wherein the inhibition current sensed by the sensor is about 33% to about 82%.