| Sensitized chemiluminescence?CL?was established to extend the analytical appliance of hydrogen peroxide-hydrogen sulfite,periodate-peroxide and Fenton systems.The detailed mechanisms for enhancement were discussed in the presence of sensitizers by EPR analysis,free radical scavenging studies,photoluminescent and CL spectra.The enhanced systems were used for the determination of different reagents and sensitive,simpler,faster and less costly methods were developed which were employed to conclude reagents in real models.The CL intensity of hydrogen peroxide with bisulfite CL system was significantly enhanced by mercaptopropanoic acid capped ZnS QDs in acidic medium.It is of worth to know that,the order of addition of reagents sturdily influences CL intensity,indicating different free radical generation in response to the different orders.Interestingly,the addition of water to an optimum concentration ensued further increase in CL signal,may be due to hydrolysis reaction at higher concentration of NaHSO3.Four emitters such as 1O2,?O2?2*,SO2*and ZnS QDs*were detected in the CL system.Mechanistic investigation indicated that QDs acted as a catalyst,firstly decomposing H2O2 to generate free radicals and secondly prompting CL by energy transfer and electron-transfer annihilation effects.Distinct from most QDs CL reactions which classically attained in basic conditions,this system operates in acidic medium.This may intrigue an avenue for investigating the CL property of QDs in an acidic medium and promote its application in various fields.The results advocated that CL of periodate and hydrogen peroxide system in the absence and existence of nitrogen doped carbon dots?N-CDs?in basic medium ensues by means of radical route.The boosted CL asset was applied for fortitude of gallic acid and pyrogallol in range of 1.0×10-4 to 1.0×10-7 M with 6.1×10-8 and 4.6×10-8 M limit of recognition,correspondingly.The attained outcomes revealed that this method was simpler sensitive,quicker and more economic likened to other approaches and may possibly be practice to conclude polyphenols in real trials.CL of Fenton system was significantly enhanced by N-CDs and investigated in detail.The mechanism of electron-hole induction in N-CDs was proposed.The radicals generated by Fenton reaction react with N-CDs and leads to oxygen incorporation in N-CDs.Detailed studies show that the enhanced CL was due to excited N-CDs which was produced through energy and electron transfer processes.The key species for producing hole and electron in N-CDs were generated by decomposition of hydrogen peroxide.Furthermore,the highest CL aptitudes of Fe2+was speculated to peroxide-induced oxidation of Fe2+while relative CL signals of Fe3+might be due to back-reaction of Fe3+to Fe2+.The CL signal remained constant after sometime due to redox cycling to establish equilibrium,irrespective to any form of iron.The N-CDs enhanced Fenton system was utilized for sensitive and selective recognition of Fe2+.The effect of different cations as well as different anions on CL intensity was checked.Moreover,it was observed that in the presence of rhodamine 6G,the emission was from rhodamine 6G rather than from N-CDs which led to the assembly of a new chemiluminescent resonance energy transfer?CRET?system.The finding was based on the slight enhancing result of rhodamine 6G,spectral overlap between emission spectrum of N-CDs and absorption spectrum of rhodamine 6G and on the CL spectra of different combinations of the CL system.Furthermore,on the basis of linear relation of CL intensity with concentration a facile,rapid and selective methodology for determination of Fe2+with 1.13 nM as lower limit in a dynamic range of 1×10-6 to 1×10-9 M was developed. |
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