A fluorescence “on–off” sensor for the highly selective and sensitive detection of Cu2+ ion

In an attempt to obtain a model of copper(II) ion-selective sensors, a new 1,8-naphthalimide-based fluorescence chemosensor, N-allylamine-4-[(E)-4-(([2-aminoethyl]imino)methyl) benzene-1,3-diol]-1,8-naphthalimide (NABN), was designed and synthesized. The sensor NABN is fully characterized by melting point analysis, fourier transform infrared spectra, Ultraviolet–visible (UV–vis) spectra, fluorescence spectra, ¹H NMR and ¹³C NMR spectroscopy, and mass spectrometry. NABN showed an unrivaled sensing behavior and an ardent selectivity toward copper(II) ion over other competitive metal ions tested in solution (N,N-Dimethylformamide (DMF)/Tris–HCl buffer, 1:1, v/v, pH = 7.2). The sensor showed a linear fluorescence quenching toward copper(II) ion in the range 0–50 μM, with a detection limit of 1.92 × 10⁻⁷ M estimated. Job's method indicated the formation of a 2:1 coordinative mode of the sensor with copper(II) ion with a high threshold of binding constant of 4 × 10¹² M⁻¹. Combining the above results, the quenching response of NABN toward Cu(II) ions could be ascribed to the strong, intrinsic paramagnetic behavior of Cu(II).     

A selective and sensitive off–on probe for palladium and its application for living cell imaging

A new rhodamine B derivative T1 has been rationally synthesized and displayed selective Pd(Ⅱ)-amplified absorbance and fluorescence emission above 540 nm in methanol–water. Upon the addition of Pd(Ⅱ), the spirolactam ring was unfolded and a 1:1 metal-ligand complex formed, which can be used for ‘‘naked-eyes" detection. In addition, fluorescence imaging experiments of Pd~(2+) in HepG2 living cells showed its valuable application in biological systems.     

Electrochemical sensor based on a carbon nanotube-modified imprinted sol–gel for selective and sensitive determination of ß2-agonists

We describe a molecularly imprinted electrochemical sensor for selective and sensitive determination of β₂-agonists. It is making use of a combination of single-wall carbon nanotubes (SWNTs) with a molecularly imprinted sol–gel. The SWNTs were introduced in order to enhance electron transport and sensitivity. The imprinted sol–gel film with its specific binding sites acts as a selective recognition element and as a preconcentrator for β₂-agonists. The morphology of the imprinted film was characterized by scanning electron microscopy. The optimized sensor displays high sensitivity and excellent selectivity for the β₂-agonists as shown for their determination in human serum samples.

Synthesis of new bis-benzylidene-hydrazides as a sensitive chromogenic sensor for naked-eye detection of CN¯ and AcO¯ ions

Some new bis-benzylidene-hydrazides were synthesized via a condensation reaction of the corresponding azo dyes with adipic acid dihydrazide. All compounds because of the three possible stereoisomers showed four sets of signals in NMR. The anion recognition studies exhibited that the nitro bis-benzylidene-hydrazide derivative acts as a highly sensitive and selective chromogenic sensor for naked-eye detection of CN¯ and AcO¯ ions, with a distinct color change from yellow to blue and yellow to purple, respectively. The limit of detection (LOD) was found for 1d toward CN¯ to be 1.1?μM. The result of the Job's plot indicated stoichiometry of binding between chemosensor and anions is found to be 1:2.     

“On–off–on” pyrene-based fluorescent chemosensor for the selective recognition of Cu2+ and S2− ions and its utilization in live cell imaging

A new “on–off–on” fluorescence chemosensor (DPD) was designed, synthesized, and characterized based on pyrene and benzothiozole hydrazide. The probe DPD shows high affinity towards Cu²⁺ ions and the DPD-Cu²⁺ ensemble shows high sensitivity towards S²⁻ ions through the displacement method in the presence of other interfering ions. The detection limits of DPD for Cu²⁺ and S²⁻ ions were found to be 0.73 and 0.87 nM, respectively. Furthermore, the receptor was effectively applied to recognize Cu²⁺ and S²⁻ ions in real samples and live A549 cells through imaging studies.     

Synthesis and characterization of a sensitive and selective Fe3+ fluorescent sensor based on novel sulfonated calix[4]arene‐based host‐guest complex

A novel fluorescent sensor was prepared from sulfonated calix[4]arene (SC4A) by the host-guest complexation method using the fluorescent dye rhodamine B (RB) as a structure-directing agent. The crystal structure of the host-guest complex (RB@(SC4A)₃) was confirmed by X-ray diffraction studies while its performance and sensing mechanism for metal ion pollutants were characterized using fluorescence and nuclear magnetic resonance spectroscopies. The results showed that RB@(SC4A)₃ had a triangular branch structure resulting from host-guest mediation of the interactions between the three SC4A host molecules and the three terminal groups of the guest molecule RB. The host-guest complex exhibited sensitive and selective sensing towards Fe³⁺ ions via a fluorescence quenching mechanism. The results indicated that RB@(SC4A)₃ could be a promising sensitive and selective fluorescent sensor for metal ion pollutants monitoring. It also provided new insights into the synthesis of calixarene-based host-guest complex.     

An efficient sensor for relay recognition of Zn and Cu through fluorescence ‘off–on–off’ functionality

A new bis(8-carboxamidoquinoline) dangled binaphthol derivatized fluorescent sensor (L) was designed and synthesized. L behaves ratiometric response to Zn²⁺ with high selectivity accompanied by remarkable emission enhancement and red shift. The resultant L–Zn²⁺ complex can act as a Cu²⁺ sensing probe with fluorescence quenching behavior through direct Zn²⁺ ion replacement. Furthermore, the binding modes of Zn²⁺ and Cu²⁺ with L are elucidated by X-ray crystallographic analysis, respectively.     

A resonance light-scattering off–on system for studies of the selective interaction between adriamycin and DNA

On the basis of the resonance light scattering (RLS) of Ag nanoparticles (AgNPs), an RLS off–on system was developed for studies of the selective interaction between adriamycin (ADM) and DNA. In this strategy, addition of ADM could induce a proportional decrease in the RLS intensity of AgNPs; this could be used to detect trace amounts of ADM with a detection limit of 12.75 ng mL⁻¹ in the range 0.021–10.0 μg mL⁻¹. Subsequently, by investigating the ability of different DNA sequences to restore the RLS intensity of the analytical systems, we found that ADM was selective to dsDNA and had an obvious preference for sequences that were rich in guanine and cytosine bases. In order to validate the results of the RLS assay, fluorescence quenching was used, and binding constants and binding numbers of each system were calculated. Compared with other methods, this RLS off–on strategy was more sensitive, fast, and reliable. It has also supplied a novel method for studying the sequence selectivity of DNA-targeted anticancer drugs and is a novel application of the RLS technique in analytical chemistry.     

Rhodamine-linked pyridyl thiourea as a receptor for selective recognition of F–, Al3+ and Ag+ under different conditions

A new rhodamine-labelled pyridyl thiourea-based compound 1 has been designed and synthesised. While the receptor selectively recognises F^– and Al³⁺ ions in CH₃CN, Al³⁺ and Ag⁺ ions are selectively screened from other cations in CH₃CN/water (4/1, v/v; 10 μM Tris–HCl buffer, pH 6.8) by observing different emission characteristics and colour changes. While Ag⁺ is sensed through an increase in emission at 416 nm, Al³⁺ is detected by a ratiometric change in emission of 1 with a band at 585 nm. The receptor shows in vitro detection of both the ions in human cervical cancer (HeLa) cells.     

Preparation and characterization of MNPs–PhSO3H as a heterogeneous catalyst for the synthesis of benzo[b]pyran and pyrano[3,2-c]chromenes

Research on Chemical Intermediates - In this study, an efficient and novel procedure has been reported for loading sulfanilic acid on the surface of magnetite Fe3O4 nanoparticles using...     

均三嗪衍生物应用于Fe3+和Cu2+的选择性识别研究

合成了2,4-二甲基-6-(4’-N,N-二甲氨基苯乙烯基)-1,3,5-均三嗪(1)和2-苯乙烯基-4,6-二甲基-1,3,5-均三嗪(2)两种化合物,并对其进行了1H NMR,MS,元素分析等表征.采用吸收光谱法研究了金属离子与化合物间的相互作用,结果显示:化合物1对Fe3+和Cu2+表现出高选择性光谱响应,其最大吸收波长由393 nm分别红移至525 nm和513 nm,溶液颜色由黄色变为粉红色.化合物1与Fe3+结合形成1∶1型配合物,其结合常数为1.8×104L mol-1;与Cu2+结合形成2∶1型配合物,其结合常数为2.6×1010L mol-1.化合物2仅对Fe3+呈现显著的光谱变化,其最大吸收波长由304nm红移至357 nm,而Cu2+的加入未引起光谱明显变化,2与Fe3+亦形成1∶1型配合物,结合常数为1.0×105L mol-1.结果表明Fe3+可能与化合物1和2中三嗪N配位,而Cu2+与化合物1中甲氨基中的N配位.同时考察了其它金属离子如Li+,K+,Mg2+,Ca2+,Co3+,Ni2+,Ag+,Cd2+,Hg2+和Zn2+等离子对化合物1和2吸收光谱的影响,结果显示两者光谱均无明显变化,据此提出了高选择性Fe3+,Cu2+的识别体系.     

铜氨络离子的形成和空间构型的探究

基于化学平衡的原理,通过简单的计算解释了氢氧化铜溶于氨水的反应机理,同时基于价键理论和Jahn-Teller效应来阐述铜氨络离子以及其他铜离子配合物的形成过程.     

A highly selective magnetic sensor with functionalized Fe/Fe3O4 nanoparticles for detection of Pb2+

A magnetic sensor for detection of Pb~(2+) has been developed based on Fe/Fe_3O_4 nanoparticles modified by3-(3,4-dihydroxyphenyl)propionic acid(DHCA). The carboxyl groups of DHCA have a strong affinity to coordination behavior of Pb~(2+) thus inducing the transformation of Fe/Fe_3O_4 nanoparticles from a dispersed to an aggregated state with a corresponding decrease, then increase in transverse relaxation time(T_2) of the surrounding water protons. Upon addition of the different concentrations of Pb~(2+) to an aq. solution of DHCA functionalized Fe/Fe_3O_4 nanoparticles(DHCA-Fe/Fe_3O_4 NPs)([Fe] = 90 mmol/L), the change of T_2 values display a good linear relationship with the concentration of Pb~(2+) from 40 μmol/L to 100 μmol/L and from 130 μmol/L to 200 μmol/L, respectively. Owing to the especially strong interaction between DHCA and Pb~(2+), DHCA-Fe/Fe_3O_4 NPs exhibited a high selectivity over other metal ions.     

A coumarin based highly selective fluorescent chemosensor for sequential recognition of Cu2+ and PPi

In this study, we have successfully synthesized a new coumarin based fluorescent chemosensor 1, in which tren and quinolone are introduced as receptors for sequential recognition of Cu²⁺ and PPi. The structure of chemosensor 1 was characterized by ¹H NMR, ¹³C NMR and ESI-HR-MS. Sensor 1 showed an obvious “on-off” fluorescence quenching response toward Cu²⁺, and the quenching efficiency reached a maximum of 99.6% with the addition of 20 equiv. of Cu²⁺. The 1-Cu²⁺ complex showed an “off-on” fluorescence enhancement response toward PPi over many competitive anions, especially HPO₄^2? and H₂PO₄^?. The detection limit of sensor 1 was 1.9?×?10^?6?M to Cu²⁺ and 5.96?×?10^?8?M to PPi. In addition, sensor 1 showed a 1:1 binding stoichiometry to Cu²⁺ and sensor 1-Cu²⁺ showed a 2: 1 binding stoichiometry to PPi in CH₃CN/HEPES buffer medium (9:1 v/v, pH?=?7.4). The stable pH range of sensor 1 to Cu²⁺ and 1-Cu²⁺ to PPi was from 4 to 8.     

One-pot diastereoselective synthesis of tetrahydroepimino-benzo[b]azocines through sequential [3+2]-cycloaddition and Staudinger-aza-Wittig reactions

The one-pot synthesis of tetrahydro-epiminobenzo[b]azocines through a sequential 1,3-dipolar cycloaddition and intramolecular Staudinger-aza-Wittig reaction sequence is reported. This methodology provides a new and efficient approach for medium-sized and bridged nitrogen heterocyclic molecules.     

含萘酚直链多胺化合物的合成及对Cu2+的识别

以β-萘酚为原料合成了两种含萘酚直链多胺化合物,并用IR、1H NMR、Ms进行了表征。利用紫外分光光度法考察了这两种化合物对金属阳离子的识别性能。实验结果表明,这两种化合物均对Cu2+具有高选择性识别能力,说明在主客体识别中分子尺寸的匹配和化合物中基团的空间合理排布是化合物和Cu2+间能发生相互作用的重要根据。     

吡咯并[2,1,5-cd]中氮茚酰腙衍生物的合成及Cu2+荧光探针行为

设计合成了吡咯并[2,1,5-cd]中氮茚酰腙衍生物6. 测试了其紫外光谱和荧光光谱, 研究了其对铜离子的选择性识别作用. 结果表明, 化合物6作为铜离子荧光探针, 受常见离子干扰较小, 对于铜离子有着较高的选择性和较低的检出限.     

First Principles Study of Ca3Sc2Si3O12:Ce3+ Phosphors

Charge compensation plays a very important role in modifying the local atomic structure and moreover the spectroscopic property of an isolated luminescent center, and so has been widely adopted in phosphor designs. In this work, we carry out first principles calculations on various cases of Ce³⁺ centers in Ca₃Sc₂Si₃O₁₂ by considering the effects of the charge compensations related to N^3-, Sc³⁺, Mn²⁺, Mg²⁺, and Na⁺. Firstly, the local structures around Ce³⁺ are optimized by using density functional theory calculations with supercell model. The 4f→5d transition energies of Ce³⁺ are then obtained from the CASSCF/CASPT2/RASSI-SO calculations performed on Ce³⁺-centered embedded clusters. The calculated energies support the previous assignments of the experimental spectra. Especially, a previously unclear peak is identified to be caused by Sc³⁺ substituting Si⁴⁺. The results show that the first principles calculations can be used as an effective tool for predicting and interpreting spectroscopic properties of the phosphors.     

阳离子胶束对[Gr(III)-(Gly-Gly)]2+与茚三酮反应动力学的影响

The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of chromium dipeptide complex ([Cr(III)-Gly-Gly]2+) with ninhydrin under varying conditions has been investigated. The rates of the reaction were determined in both water and surfactant micelles in the absence and presence of various organic and inorganic salts at 70 ℃ and pH 5.0. The reaction followed first-and fractional-order kinetics with respect to [Cr(III)-Gly-Gly2+] and [ninhydrin]. Increase in the total concentration of CTAB from0 to 40×10-3mol·dm-3 resulted in an increase in the pseudo-first-order rate constant (kψ) by a factor of ca 3. Quantitative kinetic analysis of kψ-[CTAB] data was performed on the basis of the pseudo-phase model of the micelles. As added salts induce structural changes in micellar systems that may modify the substrate-surfactant interactions, the effect of some inorganic (NaBr, NaCl, Na2SO4) and organic (NaBenz, NaSal, NaTos) salts on the rate was also explored. It was found that the tightly bound counterions (derived fromorganic salts) were the most effective.     

Catalyst-Free [3+2] Cycloaddition of Isoquinolinium/Pyridinium Ylides and Electron-Deficient Alkenes

The development of simple-to-operate methods for the preparation of indolizidine derivatives are of great importance. A mild one-pot protocol for the [3+2] cycloaddition of isoquinolinium/pyridinium ylides and electron-deficient alkenes using NaBH₃CN as reductant has been developed. The protocol has a broad substrate scope (more than 40 examples) and provides various novel hexahydroindolizidine derivatives in high yields and excellent diastereoselectivities (up to >20/1).