Carbon quantum dots from hemicucur[6]bit and the application for the detection of Pb.

A macrocyclic compound, hemicucurbit[6]uril (HemiQ[6]), is employed as the carbon source to produce a novel sort of carbon quantum dots (CQDs) with blue fluorescence in aqueous solution. The CQDs are fully identified by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Nuclear Magnetic Resonance (NMR), zeta potential, ultraviolet/visible (UV-vis) and photoluminescence spectroscopy (PL). The nanomaterial is developed for the analysis of Pb in the light of the Resonance Rayleigh scattering (RRS) changes with the increasing Pb concentration.

Selective removal of CrO in aqueous solution by nonporous pure crystals of cucurbit[6]uril.

Cucurbit[6]uril (Q[6]) could serve as a selective absorbent for the toxic anion CrO, which was demonstrated by the results of UV-vis, ICP, XPS, SEM, and EDS experiments. Single-crystal X-ray diffraction analysis revealed that capture capacity could be attributed to the outer-surface interactions of cucurbit[]uril between CrO and the outer surface of Q[6].

Supramolecule-Controlled Enantioselectivity for Electrochemical Asymmetric Hydrogenation of Coumarins with a Chiral Macrocyclic Compound.

The supramolecular strategy was subjected to the asymmetric hydrogenation of 4-methylumbelliferone by electrochemical reduction in the presence of a chiral macrocyclic multifarane[3,3], which offered a l-7-hydroxy-4-methylchroman-2-one product with a chemical yield of 65% and enantioselectivity up to >99% ee. The high stability of the developed chiral supramolecular electrode guaranteed the recyclability and repeatability in the electrolysis, and therefore, the application was extended to more coumarin derivatives to provide satisfactory chemical yields and enantioselectivities.

Recent Breakthroughs in Supercapacitors Boosted by Macrocycles.

Supercapacitors are essential for electrochemical energy storage because of their high-power density, good cycle stability, fast charging and discharging rates, and low maintenance cost. Macrocycles, including cucurbiturils, calixarene, and cyclodextrins, are cage-like organic compounds (with a nanocavity that contains O and N heteroatoms) with unique potential in supercapacitors. Here, we review the applications of macrocycles in supercapacitor systems, and we illustrate the merits of organic macrocycles in electrodes and electrolytes for improving the electrochemical double-layer capacitors and pseudocapacitance via supramolecular strategies.

Highly selective recognition of the Al(ClO) molecule by a mono-pyrene substituted thiacalix[4]arene chemosensor.

A mono-pyrene substituted thiacalix[4]arene chemosensor (TCA-Py) was successfully synthesized in satisfactory yield. Fluorescence analysis revealed that TCA-Py exhibited a high recognition selectivity toward the Al(ClO) molecule due to the synergy between the Al cation and ClO anion. This unique ability to recognise an entire inorganic molecule broadens the field of molecular recognition.

Quantitatively Switchable pH-Sensitive Photoluminescence of Carbon Nanodots.

pH sensing plays a key role in the life sciences as well as the environmental, industrial, and agricultural fields. Carbon nanodots (C-dots) with small size, low toxicity, and excellent stability hold great potential in pH sensing as nanoprobes due to their intrinsic pH-sensitive photoluminescence (PL). Nonetheless, the undesirable sensitivity and response range of C-dot PL toward pH cannot meet the requirements of practical applications, and the unclear pH-sensitive PL mechanism makes it difficult to control their pH sensitivity.

Molecular Tweezers-like Calix[4]arene Based Alkaline Earth Metal Cation (Ca, Sr, and Ba) Chemosensor and Its Imaging in Living Cells and Zebrafish.

Although alkaline earth metal cations play an important role in our daily life, little attention has been paid to the field of fast quantitative analysis of their content due to a lack of satisfactory precision and a fast and convenient means of detection. In this study, we have designed a set of molecular tweezers based on the calix[4]arene chemosensor , which was found to exhibit high selectivity and sensitivity toward Ca, Sr, and Ba (by UV-vis and fluorescence methods) with low detection limits of the order of 10 to 10 M and high association constants (of the order of 10). More significantly, sensor not only can recognize Ca, Sr, and Ba but also can further discriminate between these three cations via the differing red shifts in their UV-vis spectra (560 nm for ·Ca, 570 nm for ·Sr, and 580 nm for ·Ba complex) which is attributed to their different atomic radii.

An efficient ICT-based ratio/colorimetric tripodal azobenzene probe for the recognition/discrimination of F, AcO and HPO anions.

The tripodal probe L was readily prepared via introducing rhodamine and azobenzene groups in a two-step procedure. Studies of the recognition properties indicated that probe L exhibited high sensitivity and selectivity towards F, AcO and HPO through a ratiometric colorimetric response with low detection limits of the order of 10 M. The complexation behaviour was fully investigated by spectral titration, H NMR spectroscopic titration and mass spectrometry.

Recognition of silver cations by multifarene[2,2] chemosensors with unexpected fluorescence response.

Fluorescent chemosensors based on a new macrocyclic compound, multifarene[2,2], with modification by triazole-linked pyrene or anthracene were synthesized. These macrocyclic sensors exhibited high affinity and selectivity toward Ag over other metal ions, with ratiometric or enhanced response of their fluorescence emissions depending upon the substituent species for coordination to Ag, and an unexpected response to a concentration threshold of the metal cations was discovered. The experimental evidences of fluorescence spectra, H NMR titration, IR spectra, and high-resolution mass spectra suggested the coordination behaviors of the sensors with Ag, that is, the 1:1 complexes were formed with moderate association constants of about 10 L·mol, and the sulfur atoms on macrocyclic ligand should affinite to the metal cations.

A three-dimensional (time, wavelength and intensity) functioning fluorescent probe for the selective recognition/discrimination of Cu, Hg, Fe and F ions.

We have strategically incorporated three different fluorophores at tren to construct a multi-energy donor/acceptor "smart" probe L. This probe operates by using three-dimensional scales (response time, wavelength and fluorescence intensity) which allows for the selective recognition and discrimination of the Cu, Hg, Fe and F ions.

Coordination supramolecular assemblies of a monohydroxycucurbit[7]uril and their potential applications in gas sorption.

Coordination supramolecular assemblies of monohydroxycucurbit[7]uril ((HO)Q[7]) with alkaline earth metal ions (AE) have been formed in aqueous HCl solution in the presence of tetrachloride cadmium anions ([CdCl]) as a structure directing agent. The driving force for the assembly could be attributed to the interaction of the positive electro-potential outer-surface of (HO)Q[7] molecules with [CdCl] anions and ionic dipole interaction of the hydroxyl of (HO)Q[7] molecules with [CdCl] anions. Moreover, the porous structure of the (HO)Q[7]/AE-based coordination supramolecular assemblies could result in potential applications in the selective sorption of polar volatile organic molecules, which may be useful in molecular sieves, sensors, absorption and separation.

Highly selective recognition of Al and I ions using a bi-functional fluorescent probe.

A tripodal fluorescent probe L1 armed with Rhodamine B and 1-naphthaleneisothiocyanates was prepared in high yield. A study of the recognition properties revealed that probe L1 exhibited high sensitivity and selectivity towards Al through a "FRET" fluorescence response and colorimetric response with low detection limits of the order of 10 M. Meanwhile, probe L1 also possessed high recognition ability for I through fluorescence decay, which given there are comparatively few selective fluorescent probes for I, is significant.

An Unprecedented Photochemical Reaction for Anthracene-Containing Derivatives.

A series of anthracene-containing derivatives have been synthesised and characterised. The photochemical behaviour of these derivatives have been investigated by H NMR spectroscopy. An unprecedented photolysis reaction for anthracene-containing derivatives was observed in the case of anthracenes directly armed with a -CH O-R group upon UV irradiation.

Click-modified hexahomotrioxacalix[3]arenes as fluorometric and colorimetric dual-modal chemosensors for 2,4,6-trinitrophenol.

A new type of chemosensor-based approach to the detection of 2,4,6-trinitrophenol (TNP) is described in this paper. Two hexahomotrioxacalix[3]arene-based chemosensors 1 and 2 were synthesized through click chemistry, which exhibited high binding affinity and selectivity toward TNP as evidenced by UV-vis and fluorescence spectroscopy studies. (1)H NMR titration analysis verified that CH⋯O hydrogen bonding is demonstrated as the mode of interaction, which possibly facilitates effective charge-transfer.

A novel fluorescence "on-off-on" chemosensor for Hg(2+)via a water-assistant blocking heavy atom effect.

Upper rim pyrene-functionalized hexahomotrioxacalix[3]arene L was synthesized via Click chemistry, and its fluorescence behaviors toward several common metal cations were investigated. L exhibited a significant fluorescence quenching response to Hg(2+) in CH3CN solution, which was unaffected by the coexistence of other competitive metal cations. Thus, L can be utilized as a highly selective and sensitive fluorescent chemosensor for Hg(2+) with a detection limit in the nM level.

A Rare and Exclusive Endoperoxide Photoproduct Derived from a Thiacalix[4]arene Crown-Shaped Derivative Bearing a 9,10-Substituted Anthracene Moiety.

A rare and exclusive endoperoxide photoproduct was quantitatively obtained from a thiacalix[4]arene crown-shaped derivative upon irradiation at λ=365 nm; the structure was unambiguously confirmed by (1) H/(13) C NMR spectroscopy and X-ray crystallography. The prerequisites for the formation of the endoperoxide photoproduct have also been discussed. Furthermore, the photochemical reaction rate could be greatly enhanced in the presence of the thiacalix[4]arene platform because it served as a host to capture oxygen.

Manganese coordination chemistry of bis(imino)phenoxide derived [2 + 2] Schiff-base macrocyclic ligands.

The [2 + 2] Schiff-base macrocycles [2,2'-(CH2CH2)(C6H4N[double bond, length as m-dash]CH)2-2,6-(4-RC6H2OH)]2 ((R)H2), upon reaction with MnCl2 (two equivalents) afforded the bimetallic complex [Cl3Mn(μ-Cl)Mn((Me)H2)] (1) or the salt complex [Cl3Mn(NCMe)][MnCl((tBu)H2)] (2). Under similar conditions, use of the related [2 + 2] oxy-bridged macrocycle [2,2'-O(C6H4N[double bond, length as m-dash]CH)2-4-RC6H2OH] (II(R)H2), afforded the bimetallic complexes [(MnCl)2II(R)] (R = Me 3, tBu 4), whilst the macrocycle derived from 1,2-diaminobenzene and 5,5'-di-tert-butyl-2,2'-dihydroxy-3,3'-methylenedibenzaldehyde (H4) afforded the complex [(MnCl)2(III)]·2MeCN (5·2MeCN). For comparative studies, the salt complexes [2,6-(ArNHCH)2-4-MeC6H2O][MnCl3(NCMe)] (Ar = 2,4-Me2C6H3, 6) and {[(2-ArN[double bond, length as m-dash]CH),6-(ArNHCH)-4-Me-C6H2O]MnCl}2[MnCl4]7·8CH2Cl2 (Ar = 4-MeC6H4, ·8CH2Cl2) were prepared.

The first study about the relationship between the extractability of thiacalix[4]arene derivatives and the position of the coordination binding sites.

Three organic ionophores (2-4) based on the p-tert-butylthiacalix[4]arene backbone, blocked in the 1,3-alternate conformation, bearing two pyridyl coordinating moieties (ortho for 2, meta for 3 and para for 4), have been synthesized and characterized in the solid state. The solvent extraction experiments with the metal ions showed that the ability of these derivatives to complex with Ag(+) appeared to be largely dependent on the position of the nitrogen atoms of the pyridyl ring. Two different complexation modes have been confirmed by 1H NMR titration.

Efficient production of flavonoids in Fagopyrum tataricum hairy root cultures with yeast polysaccharide elicitation and medium renewal process.

Background: Tartary buckwheat (Fagopyrum tataricum), an excellent edible and medicinal crop, has been widely used as a daily diet and traditional medicine for a long time. The major functional components of Fagopyrum tataricum have been demonstrated to be flavonoids (i.e.

Response surface modeling and optimization of ultrasound-assisted extraction of three flavonoids from tartary buckwheat (Fagopyrum tataricum).

Background: Buckwheat (Fagopyrum spp., Polygonaceae) is a widely planted food crop. Flavonoids, including quercetin, rutin, and kaempferol, are the main bioactive components in tartary buckwheat (Fagopyrum tataricum (L.

Rapid and simple method for the determination of emodin in tartary buckwheat (Fagopyrum tataricum) by high-performance liquid chromatography coupled to a diode array detector.

A simple and rapid method for determining emodin, an active factor presented in tartary buckwheat (Fagopyrum tataricum), by high-performance liquid chromatography coupled to a diode array detector (HPLC-DAD) has been developed. Emodin was separated from an extract of buckwheat on a Kromasil-ODS C(18) (250 mm × 4.6 mm × 5 μm) column.

An NBD-armed thiacalix[4]arene-derived colorimetric and fluorometric chemosensor for Ag+: a metal-ligand receptor of anions.

A new type of thiacalix[4]arene-based chemosensor 2a and 2b containing amino groups as a binding site and 7-nitrobenzo-2-oxa-1,3-diazole (NBD) as a chromophore have been synthesized and characterized by single crystal X-ray diffraction and by NMR spectroscopic methods. Each receptor acted as a strong colorimetric and fluorometric sensor for silver ions and exhibited significant stepwise deprotonation of NH as evidenced by a bathochromic shift in both the UV-vis absorption and fluorescence emission spectra after addition of an Ag(+) cation. Furthermore, the metal-ligand complex 2a·Ag(+) can be exploited as an ion-pair receptor for the recognition of F(-), AcO(-) or I(-) anions through switching the detection signal output (can been distinguished by 'naked eye').

[The spectroscopic properties of a new rhodamine B Schiff-base fluorescent derivative].

A derivative with Schiff-base structure was synthesized. Fluorescence and visible absorption spectra show that the presence of Fe3+ induces the formation of a Fe3+ complex, observing significant enhancement of fluorescence and absorption. The results show that the derivative is not only a good fluorescence and colorimetric chemosensor for Fe3+, but also a metal complex fluorescent probe for BSA.

Effects of biotic and abiotic elicitors on cell growth and tanshinone accumulation in Salvia miltiorrhiza cell cultures.

This study examined the effects of biotic and abiotic elicitors on the production of diterpenoid tanshinones in Salvia miltiorrhiza cell culture. Four classes of elicitors were tested, heavy metal ions (Co2+, Ag+, Cd2+), polysaccharides (yeast extract and chitosan), plant response-signaling compounds (salicylic acid and methyl jasmonate), and hyperosmotic stress (with sorbitol). Of these, Ag (silver nitrate), Cd (cadmium chloride), and polysaccharide from yeast extract (YE) were most effective to stimulate the tanshinone production, increasing the total tanshinone content of cell by more than ten-fold (2.

Kramers escape rate in nonlinear diffusive media.

In this paper, we study nonlinear Kramers problem by investigating overdamped systems ruled by the one-dimensional nonlinear Fokker-Planck equation. We obtain an analytic expression for the Kramers escape rate under quasistationary conditions by employing a metastable potential and its predictions are in excellent agreement with numerical simulations. The results exhibit the anomalies due to the nonlinearity in W that the escape rate grows with D and drops as mu becomes large at a fixed D.