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1.
The effects of hydrostatic pressure on the fluorescence of tyrosine (Tyr) solution with different concentrations of copper ion (Cu 2+) were investigated. The fluorescent intensity of pure Tyr aqueous solution enhanced with the increase of hydrostatic pressure, the fluorescent intensity increased by 8.8% when the pressure was up to 60 MPa. The fluorescence of Tyr aqueous solution was quenched obviously due to complex formation with Cu 2+ and the quenching became stronger when the concentration of Cu 2+ was higher. When the concentration ratio of Cu 2+ and Tyr ([Cu 2+]/[Tyr]) increased from 0 to 40, the fluorescent intensity decreased to 19.0% at 0.1 MPa and 24.2% at 60 MPa. It was also found that the effects of pressure on the fluorescent intensity of Tyr aqueous solution were different at various [Cu 2+]/[Tyr]. The fluorescent intensity increased by 14.4% and 38.4% for 1 and 40 ratio respectively when the pressure was changed from 0.1 MPa to 60 MPa. 相似文献
2.
An investigation of the mechanism of the fluorescence quenching by Cu 2+ for a conjugated polymer system initially designed as a fluorescence “turn-on” chemosensor based on chelation enhanced fluorescence
(CHEF) is described in this paper. Unlike all other metal cations tested, the polymer/Cu 2+ hybrid system with a 1:1 ratio between the receptor and Cu 2+ has only weak fluorescence with λ max = 490 nm and a quantum yield of 0.004 in THF at room temperature. In solvent glasses at 77 K the fluorescence remained quenched
suggesting that the quenching mechanism was due to energy transfer between the Cu 2+ and the conjugated polymer backbone. The energy transfer quenching competes effectively with the electron transfer involved
in the CHEF resulting in a more selective chemosensory system.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
利用稀土直接掺杂工艺合成了一种“常光充能”型电子陷获材料CaS:Eu,Sm,它不仅具有CaS:Eu无机发光材料的荧光光谱特性,而且具有红外升频转换特性,可将0.8~1.6μm的红外光直接转换为~672nm的红光、量子效率高达76%,是一种优于CaS:Eu的光转换农膜添加剂.而共掺Eu 2+、Sm 3+和Cu +的CaS荧光粉有望成为一种性能优于光转换农膜添加剂CaS:Eu 2+,Cu +、可人工模拟叶绿素吸收光谱的新型农用转光膜材料. 相似文献
4.
Selective quenching of luminescence of quantum dots (QDs) by Cu 2+ ions vis-à-vis other physiologically relevant cations has been reexamined. In view of the contradiction regarding the mechanism,
we have attempted to show why Cu 2+ ions quench QD-luminescence by taking CdS and CdTe QDs with varying surface groups. A detailed study of the solvent effect
and also size dependence on the observed luminescence has been carried out. For a 13% decrease in particle diameter (4.3 nm
→3.7 nm), the quenching constant increased by a factor of 20. It is established that instead of surface ligands of QDs, conduction
band potential of the core facilitates the photo-induced reduction of Cu (II) to Cu (I) thereby quenching the photoluminescence.
Taking the advantage of biocompatibility of dendrimer and its high affinity towards Cu 2+ ions, we have followed interaction of Cu 2+-PAMAM and also dendrimer with the CdTe QDs. Nanomolar concentration of PAMAM dendrimer was found to quench the luminescence
of CdTe QDs. In contrast, Cu 2+-PAMAM enhanced the fluorescence of CdTe QDs and the effect has been attributed to the binding of Cu 2+-PAMAM complex to the CdTe particle surface. The linear portion of the enhancement plot due to Cu 2+-PAMAM can be used for determination of Cu 2+ ions with detection limit of 70 nM. 相似文献
5.
A new metal ion-responsive azo-based fluorescent probes have been synthesized and characterized by NMR spectral techniques.
Steady-state fluorometric study has been used to analyze the spectroscopic and photophysical characteristics of dye derivatives
in various solvents. The fluorescence properties of these dyes are strongly solvent dependent, the wavelength of maximum fluorescence
emission shifts to the red. The Kamlet-Taft and Catalan’s solvent scales were found to be the most suitable for describing
the solvatochromic shifts of the absorption and fluorescence emission. The hydroxy substituted azo dye formed complexes with
several metal ions (Co 2+, Hg 2+, Ni 2+ and Cu 2+) and fluorescence quenching with metal ions reveal that it can be used as a new fluorescence sensor to detect the Cu 2+ ion. 相似文献
6.
Nitrogen-doped graphene quantum dots (N-GQDs) with high blue fluorescence efficiency were synthesized by the hydrothermal method from p-Phenylenediamine and p-Coumaric acid. The N-GQDs possess several superiorities, most significantly in excellent solubility and superior photostability. Besides, the as-prepared N-GQDs exhibit a uniform size distribution with a diameter of about 3.8 ± 0.5 nm. After dispersing the N-GQDs in water, the formed aqueous solution still presents a stable and homogeneous phase even after 2 months at room temperature. The N-GQD dispersion was further utilized as sensing probes for the selective detection of copper ions (Cu 2+), which is realized by the photoluminescence (PL) quenching of N-GQDs after adding Cu 2+. The detection limit for Cu 2+ was found to be 57 nM L −1, with superior selectivity in the presence of other commonly interfering metal ions. The presented results in this study provide a facile and high-efficiency method for synthesizing N-GQDs, with ultra-high detectivity and selectivity for Cu 2+ detection, offering numerous opportunities for the development of biosensing, bioimaging, environment monitoring, and others. 相似文献
7.
We developed a new fluorescent nanocomposite by using a layer-by-layer approach to link NaYF 4:Ce,Tb rare-earth (RE) nanocrystals and CdSe/ZnSe semiconductor quantum dots (QDs) with opposite charges. Under ultraviolet
light excitation, the nanocomposites exhibited both the green Tb emission centered at 550 nm, and the red QD emission at 650 nm.
Sensing applications showed that the red QD emission was quenched by trace amount of Cu 2+ (or Ag +) ions due to the ion displacement mechanism, while the green RE emission kept constant. Thus, the nanocomposites with the
decreased QD/RE emission intensity ratio and changed fluorescence output color provided a visible “indicator” to detect metal
ions quantificationally. In comparison with single emission materials, the dual emission nanocomposites can be a more reliable
probe for various sensing applications. 相似文献
8.
Free-standing powders of doped ZnS nanoparticles have been synthesized by using a chemical co-precipitation of Zn 2+, Mn 2+, Cu 2+ and Cd 2+ with sulfur ions in aqueous solution. X-ray diffraction analysis shows that the diameter of the particles is ∼2–3 nm. The
unique luminescence properties, such as the strength (its intensity is about 12 times that of ZnS nanoparticles) and stability
of the visible-light emission, were observed from ZnS nanoparticles co-doped with Cu 2+ and Mn 2+. The nanoparticles could be doped with copper and manganese during the synthesis without altering the X-ray diffraction pattern.
However, doping shifts the luminescence to 520–540 nm in the case of co-doping with Cu 2+ and Mn 2+. Doping also results in a blue shift on the excitation wavelength. In Cd 2+-doped ZnS nanometer-scale particles, the fluorescence spectra show a red shift in the emission wavelength (ranging from 450 nm
to 620 nm). Also a relatively broad emission (ranging from blue to yellow) has been observed. The results strongly suggest
that doped ZnS nanocrystals, especially two kinds of transition metal-activated ZnS nanoparticles, form a new class of luminescent
materials.
Received: 16 October 2000 / Accepted: 17 October 2000 / Published online: 23 May 2001 相似文献
9.
A new pyrene derivative (chemosensor 1) containing a picolinohydrazide moiety exhibits high selectivity for Cu 2+ ion detection in mixed aqueous media (CH 3OH:H 2O = 7:3). Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu 2+. However, the metal ions Ag +, Ca 2+, Cd 2+, Co 2+, Cu 2+, Fe 2+, Fe 3+, Hg 2+, K +, Mg 2+, Mn 2+, Ni 2+, Pb 2+, and Zn 2+ produced only minor changes in fluorescence for the system. The apparent association constant ( K
a) of Cu 2+ binding in chemosensor 1 was found to be 2.75*10 3 M −1. The maximum fluorescence enhancement caused by Cu 2+ binding in chemosensor 1 was observed over the pH range 5–8. Moreover, by means of fluorescence microscopy experiments, it is demonstrated that 1 can be used as a fluorescent probe for detecting Cu 2+ in living cells. 相似文献
10.
We have rationally constructed a novel ratiometric and near-infrared Cu 2+ fluorescent probe based on a tricarbocyanine chromophore. The new probe NIR-Cu showed a ratiometric fluorescent response to Cu 2+ with a large emission wavelength shift (up to 142 nm) in the far-red to near-infrared region. The probe also displayed a large variation in the fluorescence ratio (I 636/I 778) to Cu 2+ species with high sensitivity and selectivity. Additionally, the developed probe NIR-Cu was suitable for fluorescence imaging of Cu 2+ in living cells and mice. 相似文献
11.
The ytterbium ions doped MO-Al 2O 3 (M=Ca, Sr and Ba) phosphors have been synthesized through combustion technique and their up and down conversion fluorescence properties have been studied and compared. The samples were calcinated at different temperatures and their FTIR and XRD spectra have shown a close relationship. With 976 nm excitation all these phosphors show cooperative upconversion emission at 488 nm from the pairs of two Yb 3+ ions along with an unexpected broad upconversion band in the blue green region and has been assigned to arise from the defect centers. Contrary to this upconversion emission, calcium aluminate phosphor exhibits bright and very broad down-conversion fluorescence (FWHM≈160 nm) upon UV (266 nm) excitation due to Yb 2+ ions. The inter-conversion between the 3+ and 2+ valence states of Yb ion has been observed on calcinations of samples in open atmosphere and has been correlated to the emission properties. The Yb 2+ ions containing calcium aluminate phosphor has been found suitable for producing broad band light in the visible region (white light). Lifetime of the emitting states of Yb 3+ and Yb 2+ ions have also been measured and discussed. 相似文献
12.
Condensation product ( L) of salicylaldehyde and semicarbazide behaves as a fluorescent sensor for Cd 2+ ion, in 1:1 DMSO:H 2O, over Mn 2+, Fe 2+, Ni 2+, Co 2+, Cu 2+, Pb 2+ and Hg 2+ ions. The emission peak of L at λ max = 520 nm, on excitation with 420 nm wavelength photons, showed an enhancement in intensity of ca 60-fold when interacted with Cd 2+ ion. The intensity was however found to remain unaltered when interacted with metal ions—Mn 2+, Fe 2+, Ni 2+, Co 2+, Cu 2+, Pb 2+ and Hg 2+. The intensity increases by approximately 20 fold on interaction with Zn 2+ ion. The increase in the fluorescent peak can be explained on the basis of photo induced electron transfer (PET) mechanism.
A 1:1 complexation between Cd 2+ and L with log β = 4.25 has been proved. 相似文献
13.
A new 7-nitrobenz-2-oxa-1,3-diazole (NBD) derived fluorescent probe ( 1) exhibiting high selectivity for Cu 2+ detection, produced significant fluorescence quenching in the presence of Cu 2+ ion, while the metal ions Ca 2+, Cd 2+, Co 2+, Fe 2+, Hg 2+, Mg 2+, Mn 2+, Ni 2+ and Zn 2+ produced only minor changes in fluorescence. The apparent association constant ( K
a) for Cu 2+ binding in chemosensor 1 was found to be 1.22 × 10 3 M −1. The maximum fluorescence quenching activity caused by Cu 2+ binding to 1 was observed over the pH range 6–10. 相似文献
14.
Herein we report a simple, single-step, cost-effective, environmentally friendly, and biocompatible approach using sodium salt of N-cholyl-L-cysteine (NaCysC) capped gold nanoclusters (AuNCs) with green emission properties at above the CMC in aqueous medium under UV-light irradiation. The primary and secondary CMC of NaCysC was found to be 4.6 and 10.7 mM respectively using pyrene as fluorescent probe. The synthesized AuNCs exhibit strong emission maxima at 520 nm upon excitation at 375 nm with a large Stokes shift of 145 nm. The surface functionality and morphology of NCs are studied by fourier transform infrared spectroscopy, dymanic light scattering studies and transmission electron microscopy. The formation of AuNCs was completed within 5 h and exhibit high stability for more than 6 months. The NaCysC templated AuNCs selectively quenches the Hg2+ ions with higher sensitivity in aqueous solution over the other metal ions. The fluorescence analysis of Hg2+ showed a wide linear range from 15 to 120 µM and a detection limit was found to be 15 nM. 相似文献
15.
We have prepared Schiff base functionalized 1,2,4-triazole and pyrene derivative for selective, sensitive, and naked eye colorimetric detection of Cu2+ in the mixed organic- aqueous media. Amongst the 18 different metal ions studied for absorption and fluorescence titration, only Cu2+ ion encourages the modification in spectral properties of Schiff base functionalized 1,2,4-Triazole and Pyrene Probe. The stoichiometric ratio of the TP-Cu2+ complex was determined to be 2:1 according to Job’s plot. The lower detection limit estimated for Cu2+ is 0.234 nM which shows excellent sensitivity and selectivity of the present analytical method towards detection of Cu2+ ion in the mixed organic-aqueous media. The present approach has been successfully utilized for the quantitative determination of Cu2+ ion from environmental aqueous solution. 相似文献
16.
A new benzothiazole-based chemosensor BTN (1-((Z)-(((E)-3-methylbenzo[d]thiazol-2(3H)-ylidene)hydrazono)methyl)naphthalen-2-ol) was synthesized for the detection of Cu2+. BTN could detect Cu2+ with “off-on” fluorescent response from colorless to yellow irrespective of presence of other cations. Limit of detection for Cu2+ was determined to be 3.3 μM. Binding ratio of BTN and Cu2+ turned out to be a 1:1 with the analysis of Job plot and ESI-MS. Sensing feature of Cu2+ by BTN was explained with theoretical calculations, which might be owing to internal charge transfer and chelation-enhanced fluorescence processes. 相似文献
17.
In this work, a green and simple one-pot route was developed for the synthesis of highly fluorescent amino-functionalized graphene quantum dots (a-GQDs) via hydrothermal process without any further modification or surface passivation. We synthesized the a-GQDs using glucose as the carbon source and ammonium as a functionalizing agent without the use of a strong acid, oxidant, or other toxic chemical reagent. The as-obtained a-GQDs have a uniform size of 3–4 nm, high contents of amino groups, and show a bright green emission with high quantum yield of 32.8%. Furthermore, the a-GQDs show effective fluorescence quenching for Cu 2+ ions which can serve as effective fluorescent probe for the detection of Cu 2+. The fluorescent probe using the obtained a-GQDs exhibits high sensitivity and selectivity toward Cu 2+ with the limit of detection as low as 5.6 nM. The mechanism of the Cu 2+ induced fluorescence quenching of a-GQDs can be attributed to the electron transfer by the formation of metal complex between Cu 2+ and the amino groups on the surface of a-GQDs. These results suggest great potential for the simple and green synthesis of functionalized GQDs and a practical sensing platform for Cu 2+ detection in environmental and biological applications. 相似文献
18.
The influence of annealing treatments and gamma-ray irradiation on the absorption and fluorescence spectra of Cr:GSGG crystals
grown by the Czochralski method has been investigated. Two absorption bands located near 686 nm and 1050 nm were weakened
markedly after the crystal was re-annealed in H 2 atmosphere, which is due to the Cr 4+ ions being de-oxidized into Cr 3+ ions. The other two weak additional absorption bands induced by gamma-ray irradiation appearing near 310 nm and 480 nm are
ascribed to the Fe 2+ ions and F-type color centers, respectively. In particular, the gamma-ray irradiation with a dose of 100 Mrad has an effect
of improving slightly the luminescence properties of Cr:GSGG crystals. The improvement mechanism is analyzed and discussed. 相似文献
19.
The present article describes the solvatochromic effect including solvent system selection, time study and a detailed complexation
study along with exploration of extraction properties of 5,11,17,23-tetrakis[(diethylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene
( 4) that bears nitrogen atom as a donor group available for chelating metal ions. Complexation properties of 4 toward selected transition metal ions have been investigated by UV-visible and fluorescence spectroscopies. The% efficiency
of 4 toward selected transition metal ions was found in order Cu 2+> Ni 2+> Hg 2+> Zn 2+> Co 2+> Cd 2+> Pb 2+. It has been noticed that 4 is not only proved to be an efficient Cu 2+ selective chromoionophore but also possesses an effective extraction property for transferring Cu 2+ ions from an aqueous to dichloromethane layer. The FT-IR spectroscopic method has also been applied for further confirmation
of the complexation phenomenon of 4 with Cu 2+ ion and found adequate. 相似文献
20.
The acyclic tridentate blue luminescent ligand ( λex=300 nm, λem=415 nm) quinoline-2-carboxaldehyde 2-pyridylhydrazone, HL, 1, was recognized as a new fluorescent chemosensor for Pd 2+. In alkaline methanol complete fluorescent quenching was observed in the presence of 2 equivalents of Pd 2+ that was further reflected in the solid phase fluorescence microscopic study.Ligand formed 1:1 complexes with Ni 2+, Cu 2+, Zn 2+, Pd 2+ and 1:2 complexes with Co 2+, Fe 2+ as obtained from Job's plot of continuous variation. The binding constants of different metal complexes (Fe 2+, Co 2+, Ni 2+, Cu 2+, Zn 2+ and Pd 2+) were estimated by fluorescence titrations. The ligand can selectively extract significant amount of Pd 2+ from the aqueous mixture of metal ions, and the extraction efficiency was increased from 80% to 95% with increase in the molar ratio of HL, 1, to Pd 2+ from 1 to 3. No significant interference was observed up to 2-fold excess addition of Cu 2+ and Zn 2+ and 100-fold excess addition of Co 2+, Fe 2+ and Ni 2+over the Pd 2+ ion concentration (1.0×10 −3 M). 相似文献
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