Studying on the steady-state and time-resolved fluorescence characteristics of melamine

Yang, Chengfang; Liu, Ying; Li, Lei; Zhang, Feng

doi:10.1016/j.saa.2009.12.079

Cited by 10 publications

(17 citation statements)

References 11 publications

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“…Most recently, fluorescence excitation spectra of melamine in water show the main excitation peak at 254 nm, with a weak contribution in the region between 260 and 320 nm. 24 Our starting powder present similar excitation features to the ones appearing in PLE measures on melamine powder after treatment at 300 C showing a broad excitation band extending from 260 nm to 400 nm as a product of a condensation process. 25 Melamine luminescence exhibits an efficient emission picked at 356 nm and $60 nm wide, with a long tail extending in the blue range, mainly originated by triplet-ground state recombination.…”

Section: Resultssupporting

confidence: 70%

“…25 Melamine luminescence exhibits an efficient emission picked at 356 nm and $60 nm wide, with a long tail extending in the blue range, mainly originated by triplet-ground state recombination. 24 The main excitation channels of Terbium ions in yttrium oxide matrix are located at energies higher than 320 nm, optimally overlapping the excitation features of melamine molecule. PLE spectrum of Y 2 O 3 :Tb 3þ , reported in Fig.…”

Section: Resultsmentioning

confidence: 97%

“…At the present, we do not have knowledge of melamine excitation spectra to compare with our results, but several works on the absorption of melamine in solution were already published. [23][24][25] According to Dewar and Paolini, 23 the main absorption band of melamine in solution of water and ethanol is dominated by a singlet-singlet transition around 240 nm with a weak shoulder at 313 nm attributed to a singlet-triplet excitation. Most recently, fluorescence excitation spectra of melamine in water show the main excitation peak at 254 nm, with a weak contribution in the region between 260 and 320 nm.…”

Section: Resultsmentioning

confidence: 99%

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Luminescence enhancement by energy transfer in melamine-Y2O3:Tb3+ nanohybrids

Stagi

Chiriu

Ardu

et al. 2015

Journal of Applied Physics

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The phenomenon of luminescence enhancement was studied in melamine-Y2O3:Tb hybrids. Terbium doped Y2O3 mesoporous nanowires were synthesized by hydrothermal method. X-ray diffraction patterns and Raman scattering spectra testified the realization of a cubic crystal phase. Organic-inorganic melamine-Y2O3:Tb3+ hybrid system was successfully obtained by vapour deposition method. Vibration Raman active modes of the organic counterpart were investigated in order to verify the achievement of hybrid system. Photoluminescence excitation and photoluminescence spectra, preformed in the region between 250 and 350 nm, suggest a strong interaction among melamine and Terbium ions. In particular, a remarkable improvement of 5D4→ FJ Rare Earth emission (at about 542 nm) of about 102 fold was observed and attributed to an efficient organic-Tb energy transfer. The energy transfer mechanism was studied by the use of time resolved photoluminescence measurements. The melamine lifetime undergoes to a significant decrease when adsorbed to oxide surfaces and it was connected to a sensitization mechanism. The detailed analysis of time decay profile of Terbium radiative recombination shows a variation of double exponential law toward a single exponential one. Its correlation with surface defects and non-radiative recombination was thus discussed

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Luminescence enhancement by energy transfer in melamine-Y2O3:Tb3+ nanohybrids

Stagi

Chiriu

Ardu

et al. 2015

Journal of Applied Physics

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“…This long-lived state is proposed to be a triplet state. Interestingly, Yang et al described an emission at ~370 nm in room-temperature solution that decays on time scales greater than 10 −8 s [34]. The large shift between the absorption and emission maximum and the long-lasting emission suggest the presence of triplet states.…”

Section: Resultsmentioning

confidence: 99%

Excited-State Dynamics of Melamine and Its Lysine Derivative Investigated by Femtosecond Transient Absorption Spectroscopy

Zhang

Beckstead

et al. 2016

Molecules

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Melamine may have been an important prebiotic information carrier, but its excited-state dynamics, which determine its stability under UV radiation, have never been characterized. The ability of melamine to withstand the strong UV radiation present on the surface of the early Earth is likely to have affected its abundance in the primordial soup. Here, we studied the excited-state dynamics of melamine (a proto-nucleobase) and its lysine derivative (a proto-nucleoside) using the transient absorption technique with a UV pump, and UV and infrared probe pulses. For melamine, the excited-state population decays by internal conversion with a lifetime of 13 ps without coupling significantly to any photochemical channels. The excited-state lifetime of the lysine derivative is slightly longer (18 ps), but the dominant deactivation pathway is otherwise the same as for melamine. In both cases, the vast majority of excited molecules return to the electronic ground state on the aforementioned time scales, but a minor population is trapped in a long-lived triplet state.

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“…It has been detected in milk [2], as result of a fraudulent addition, with the purpose of increasing the apparent protein level [3]. Melamine, when combined with cyanuric acid (hydrolysis product) precipitates, leading to the formation of kidney stones, which can be lethal [4].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of a Molecularly Imprinted Polymer for Melamine Analysis in Milk by HPLC with Diode Array Detection

2015

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Abbreviations:AIBN -azobisisobutyronitrile; CL -cross-linker; EDMA -ethylene glycol dimethacrylate; Kd -dissociation constant; MAA -methacrylic acid; MIDE -molecularly imprinted dispersive extraction; MIP -molecularly imprinted polymer; NIP -nonimprinted polymer; PVA -polyvinyl alcohol; Qmax -maximum binding concentration; Rrecovery; T -template. Keywords:Molecularly imprinted polymer (MIP), matrix effect, molecularly imprinted dispersive extraction coupled with high-performance liquid chromatography. 2 AbstractA molecularly imprinted polymer for melamine was prepared by suspension polymerization, using melamine as template, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linker.The optimal template/monomer and monomer/cross-linker ratios were obtained, being defined as 1/15 and 1/12, respectively. The template removal was performed by Soxhlet extraction with methanol containing 10% of acetic acid, in two cycles of 24 h each. Under optimal conditions the imprinted polymer was used as a dispersive extraction sorbent to extract melamine from different milk samples, before HPLC-DAD analysis.The validated method presented a limit of detection of 0.6 mg/kg. From the analysis of six different milks, melamine was detected in two of the considered samples in a maximum concentration of 9.3 ± 0.3 mg/kg.3

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Studying on the steady-state and time-resolved fluorescence characteristics of melamine

Cited by 10 publications

References 11 publications

Luminescence enhancement by energy transfer in melamine-Y2O3:Tb3+ nanohybrids

Luminescence enhancement by energy transfer in melamine-Y2O3:Tb3+ nanohybrids

Excited-State Dynamics of Melamine and Its Lysine Derivative Investigated by Femtosecond Transient Absorption Spectroscopy

Synthesis of a Molecularly Imprinted Polymer for Melamine Analysis in Milk by HPLC with Diode Array Detection

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