Polydiacetylene rhodamine-based colorimetric chemosensor for Au3+ detection.

A novel platform of a polydiacetylene combined with rhodamine B (PDA-Rho) colorimetric chemosensor array was prepared from a diacetylene monomer and rhodamine B derivative. Rhodamine B derivative as the ion-recognition element was embedded in the polydiacetylene matrix. To fabricate chemosensor, diacetylene monomer connected rhodamine B derivatives (DA-Rho) was coated onto a filter paper surface via drop-casting technique and transformed to polydiacetylene by polymerisation through ultraviolet (UV) irradiation. From the result, PDA-Rhoen exhibited high sensitivity and selectivity for Au3+ and could be monitored directly by naked eyes providing a fast, portable and easy-to-use as a molecular device in the real system. The DFT calculation results showed a stable complex between PDA-Rho and Au3+. We believe that, this method offers a sensitive and accurate process for Au3+ ion detection in real environmental and biological applications.

An ultra-low detection limit gold(III) probe based on rhodamine-covalent hydrogel sensor.

A highly sensitive and selective optical chemosensor (Arg-Rhoen) for determination of Au3+ was prepared by covalent immobilization of rhodamine ethylenediamine on agarose gel. Spectrophotometric studies of complex formation, chemical structures and purity of the hydrogel sensor were carried out using TGA, NMR, TEM, and IR. The complexation study results indicated that this probe can selectively detect Au3+ via a metal ion chelation-induced ring-opening reaction, and then caused a remarkable colour change from colourless to pink and a strong fluorescence enhancement. Theoretical DFT calculation results suggested that the hydrogel sensor Arg-Rhoen formed stable complexes with Au3+ through a large number of cation-dipole interactions. Reusability has been established by repeatedly dipping and rinsing the hydrogel in aqueous Au3+ and EDTA in basic solutions. We believe that this approach may provide an easily measurable and inherently sensitive method for Au3+ detection in environmental and biological applications.

Interaction investigation of single and multiple carbon monoxide molecules with Fe-, Ru-, and Os-doped single-walled carbon nanotubes by DFT study: applications to gas adsorption and detection nanomaterials.

Due to the large surface area and unique electronic property, single-wall carbon nanotube (SWCNT) is being used for adsorption and detection nanomaterials, which can be used to reduce the CO pollution effect on the environment. In the present work, the adsorptions of single and multiple CO molecules on pristine and transition metal (TM = Fe-, Ru-, and Os)-doped SWCNT were investigated in terms of geometric, energetic, and electronic properties using density functional theory calculation. Calculated results display that the adsorption of CO molecule on the SWCNTs is energetically favorable. The TM-doped SWCNT are more highly interactive to CO adsorption than that of pristine SWCNT. An Os-doped SWCNT displays the strongest interaction with single and multiple CO molecules comparing with the Fe- and Ru-doped SWCNT. The TM doping on SWCNT can induce the charge transfer between CO molecule and the SWCNT. The energy gap and density of state are clearly changed when CO molecule interacts with TM-doped SWCNT, resulting in dramatic changes of their electronic properties. Therefore, TM-doped SWCNT are possibly used as potential CO storages/absorbents or sensor material for CO detection in the environment. Graphical abstract.

Gold sensing with rhodamine immobilized hydrogel-based colorimetric sensor.

A highly sensitive and selective optical membrane for determination of Au3+ was synthesized by immobilization of a rhodamine derivative on agarose hydrogel. The sensing dye was synthesized by solvatochromism of rhodamine B via rhodamine lactone-zwitterion equilibrium. UV-vis spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were employed to confirm that the rhodamine-lactone (RhoL) was incorporated into the agarose hydrogel. The results showed that the sensor was highly selective for recognizing Au3+ over other metal ions in real systems. In addition, DFT calculation results suggested that the membrane sensor formed stable complexes with Au3+ through a large number of cation-dipole and ion-ion interactions. In addition, according to changes in signaling upon adding various Au3+ concentration, the limit of detection of Arg-RhoL for Au3+ is calculated to be 5 µM. This approach may provide an easily measurable and inherently sensitive method for Au3+ ion detection in environmental and biological applications.

Optical chemosensors for Cu(II) ion based on BODIPY derivatives: an experimental and theoretical study.

Two BODIPY derivatives for Cu(2+) ion chemosensors containing 4-[2-(diethylamino)-2-oxoethoxy]phenyl (BDP1) and 3,4-bis[2-(diethylamino)-2-oxoethoxy]phenyl (BDP2) were synthesized by coupling appropriate N,N-diethyl-2-(4-formylphenoxy)acetamide and 2,4-dimethylpyrrole moieties in the presence of trifluoroacetic acid and anhydrous dichloromethane at room temperature. The binding abilities between these chemosensors and 50 equivalents of Na(+), K(+), Ag(+), Ca(2+), Fe(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+) ions were studied using UV-vis and fluorescence spectrophotometry. The results show that, compared to other ions, both the UV-vis absorption and fluorescence emission intensity of BDP2 decreased dramatically when Cu(2+) ion was added. To explain this behavior, ab initio quantum chemical calculations were performed using correlated second-order Møller-Plesset perturbation theory (MP2/LanL2DZ). The calculated orbital energies indicated that the decrease in UV-vis absorption intensity and the quenching of fluorescene emission were due to the single-electron reduction of Cu(2+) to Cu(+) ion.

Density functional investigation of CO adsorption on Ni-doped single-walled armchair (5,5) boron nitride nanotubes.

The adsorption of CO onto Ni-doped boron nitride nanotubes (BNNTs) was investigated using density functional theory at the B3LYP/LanL2DZ level of theory. The structures of the Ni-doped BNNTs and their CO-adsorbed configurations were obtained. It was found that the strength of adsorption of CO onto Ni-doped perfect BNNTs is higher than that on defective BNNTs. The electronic properties of all of the adsorption configurations of CO on Ni-doped BNNTs are reported.

Fluorescent sensors based on BODIPY derivatives for aluminium ion recognition: an experimental and theoretical study.

Two BODIPY derivative sensors for metal ion recognition containing 10-(4-hydroxyphenyl) (L1) and 10-(3,4-dihydroxyphenyl) (L2) were synthesized in a one-pot reaction of benzaldehyde derivative and 2,4-dimethylpyrrole in the presence of trifluoroacetic acid as catalyst. The binding abilities between these sensors and 50 equivalents of Na(+), K(+), Ag(+), Ca(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Pb(2+), Al(3+) and Cr(3+) ions were studied using UV-vis and fluorescent spectroscopic methods. Of all the metal ions tested, Al(3+) ion showed the greatest decrease in intensity in the spectra of the sensors, and therefore Al(3+) ion forms the strongest complex. The binding abilities of BODIPY receptors with Na(+), Ag(+), Ca(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+) and Al(3+) ions were also investigated using density functional theory (DFT) calculations at B3LYP/LanL2DZ theoretical level. The calculated results point to the same conclusion. DFT calculations also provided the HOMO-LUMO energy levels, which can explain the spectrum change upon complexation.

Density functional investigation of hydrogen gas adsorption on Fe-doped pristine and Stone-Wales defected single-walled carbon nanotubes.

The adsorptions of hydrogen molecule of the Fe - doped pristine and Stone - Wales defected armchair (5,5) single - walled carbon nanotubes (SWCNTs) compared with the pristine SWCNT were investigated by using the density functional theory at the B3LYP/LanL2DZ level. The doping of Fe atom into SWCNTs occurring via an exothermic process was found. The adsorptions of hydrogen molecule on the Fe - doped structures of either perfect or SW defected SWCNTs are stronger than on their corresponding undoped structures. The structural and electronic properties of the pristine and SW defected SWCNTs, their Fe - doped structures and their hydrogen molecule adsorptions are reported.

Gas adsorption on the Zn-, Pd- and Os-doped armchair (5,5) single-walled carbon nanotubes.

The adsorption of NO(2), NH(3), H(2)O, CO(2) and H(2) gases on the undoped, Zn-, Pd- and Os-doped armchair (5,5) single-walled carbon nanotubes (SWCNTs) were studied using density functional method. The adsorptions of these five gases on the Zn-, Pd- and Os-doped SWCNTs are obviously stronger than on the undoped SWCNT and their adsorption abilities are in the same order: NO(2) > NH(3) > H(2)O > CO(2) > H(2). Adsorption energies for all the studied gases on the undoped, Zn-, Pd- and Os-doped SWCNTs computed at the B3LYP/LanL2DZ level are reported.

Facile synthesis of rhodamine-based highly sensitive and fast responsive colorimetric and off-on fluorescent reversible chemosensors for Hg2+: preparation of a fluorescent thin film sensor.

Fluorescence-active chemosensors (L1-L4), comprising a rhodamine scaffold and a pseudo azacrown cation-binding subunit, have been proposed and characterized as a fluorescent chemosensor for Hg(2+). An on-off type fluorescent enhancement was observed by the formation of the ring-opened amide form of the rhodamine moiety, which was induced by the interactions between Hg(2+) and the chemosensor. Upon the addition of Hg(2+), an overall emission change of 350-fold was observed, and the selectivity was calculated to be 300 times higher than Cu(2+) for receptors L2-L4. A polymeric thin film can be obtained by doping poly(methyl methacrylate) or PMMA with chemosensor L2. Such a thin film sensor can be used to detect Hg(2+) with high sensitivity and can be recovered using diluted NaOH.

Design and synthesis of thiourea based receptor containing naphthalene as oxalate selective sensor.

The thiourea based receptor containing naphthalene groups (1), has been successfully designed and synthesized for application as an oxalate receptor. A density functional theory at B3LYP/6-31G(d,p) level of theory has been applied to predict the binding ability between 1 and selected anions, i.e., oxalate, malonate, succinate, glutarate, dihydrogen phosphate, and hydrogen sulphate. Calculation results point out that receptor 1 shows the strongest interaction to oxalate ion with the binding free energy of 172.48 kcal mol(-1). The recognition ability of 1 to the selected anions has been also investigated by means of the absorption and emission techniques. Experimental results are in excellent agreement with the calculation data in which receptor 1 shows highly selective for oxalate ion over the other anions with logbeta of 3.82 (0.02) M(-1) by means of the size of binding cavity.

Molecular model for host­guest interaction of tetraamino-tert-butylthiacalix[4]arene and tetraamino-tert-butylcalix[4]arene receptors with carboxylate and dicarboxylate guests: an ONIOM study.

Geometry optimizations of tetraamino-tert-butylthiacalix[4]arene (tatbtc4a) and tetraamino-tert-butylcalix[4]arene (tatbc4a) complexes with acetate, oxalate,malonate, succinate, glutarate, adipate, and pimelate were carried out using the integrated MO:MO method. Thermodynamic quantities, preorganization energies and complexation energies of these complexes were obtained at the ONIOM(B3LYP/6-31G(d):AM1) level of theory. The relative stabilities of the tatbtc4a and tatbc4a complexes with carboxylate guests are reported. The complexes tatbtc4a/malonate and tatbc4a/oxalate were found to be the most stable species. The selectivity of the tatbtc4a receptor toward to malonate with respect to oxalate, in terms of selectivity coefficient, K(oxalatemalonate) is 9.90×10(2).

A DFT investigation of conformational geometries and interconversion equilibria of phenylthiosemicarbazone and its complexation with zinc.

The geometrical structures of phenylthiosemicarbazone (HAPhTSC) conformers have been obtained by geometry optimizations using density functional theory (DFT) calculations at the B3LYP/6-31G(d) and B3LYP/6-311G(d,p) levels of theory. Six thioamino and 24 thioimino tautomers of HAPhTSC have been found. Six tautomerization reactions between thioamino and thioimino tautomers occurring via transition states and their corresponding activation energies have been obtained. Conformational pathways for tautomerizations and interconversions of HAPhTSC conformers have been presented. Tautomerization between the most stable species of thioamino (Atttcc) and its thioimino (Itttcct) tautomer is an endothermic reaction, Delta H(0)=18.17 kcal mol(-1) and its log K=-13.74, at 298.15 K. Thermodynamic quantities of tautomerizations, interconversions of HAPhTSC conformers and their equilibrium constants are reported. The geometry of the zinc complex with HAPhTSC, found as a Zn(HAPhTSC)2Cl2 structure, has been obtained using B3LYP/6-31G(d) calculations. Binding of the Zn(HAPhTSC)2Cl2 complex is an exothermic and spontaneous reaction. [figure]. Conformational notation defined as a name consisting of a letter "A" for A thioamino tautomer followed by "c" for cis or "t" for trans isomerism of five dihedral angles of chi(C4-C3-C2-N3), phi(C3-C2-N3-N2), psi(C2-N3-N2-C1), theta;(N3-N2-C1-N1) and omega(N2-C1-N1-H2), serially, or a letter "I" for B thioimino tautomer followed by "c" for cis or "t" for trans isomerism of six dihedral angles of chi(C4-C3-C2-N3), phi(C3-C2-N3-N2), psi(C2-N3-N2-C1), theta(N3-N2-C1-N1), omega(N2-C1-N1-H2) and delta (N2-C1-S-H1), serially.