Chunying He

A multiwalled carbon nanotube/tetra-β-isoheptyloxyphthalocyanine cobalt(II) composite with high dispersibility for electrochemical detection of ascorbic acid

A sensitive electrochemical sensor for ascorbic acid (AA) is designed and synthesized via the following steps. The novel tetra-β-isoheptyloxyphthalocyanine cobalt(ii) (PcCo) spontaneously adsorbs on the surface of acid-treated multi-walled carbon nanotubes (aMWCNTs). Then, the aMWCNT/PcCo composite was immobilized on the glassy carbon electrode (GCE). The results of UV-vis, FT-IR, TG, XPS, SEM and TEM revealed the successful self-assembly between PcCo and aMWCNTs via the π-π stacking interaction, and the aMWCNT/PcCo composite appears to have a uniform network-like structure on the GCE surface due to the four peripheral isoheptyl substituents of PcCo. Such a structure can effectively increase the electrode area, facilitate the mass transport of analytes and provide continuous conducting pathways for the transportation of electrons. Synchronously, benefitting from the synergistic effect between PcCo and aMWCNTs, the obtained electrochemical sensor has a high current and low potential for the oxidation of AA. The linear range for the AA detection is from 10 μM to 1.2 mM and the detection limit is as low as 4.0 μM. The developed biosensor exhibited good reproducibility and acceptable stability, providing a simple method for the analysis of AA.

Excited-state nonlinearity measurements of ZnPcBr 4 /DMSO

Excited-state absorptive and refractive nonlinearities of a ZnPcBr4/DMSO solution are studied using a modified picosecond time-resolved pump-probe system based on a 4f nonlinear imaging technique with phase object. With the help of additional nanosecond laser Z-scan measurements, the parameters associated with the five-level model used to interpret the experimental results are uniquely determined. Unusually large absorption cross sections for the first singlet excited state and for the lowest triplet excited state as well as a rather short intersystem crossing time are found in this system, suggesting ZnPcBr4 (a phthalocyanine) to be an effective optical limiter. The intensity-dependent refractive index of neat dimethyl sulfoxide (DMSO) and the excited-state contribution to the nonlinear refractive index of the solution are also determined.

The effects of central metals on the photophysical and nonlinear optical properties of reduced graphene oxide–metal(II) phthalocyanine hybrids

Reduced graphene oxide-metal(II) phthalocyanine (RGO-MPc, M = Cu, Zn and Pb) hybrid materials have been prepared by the covalent functionalization method. The resultant RGO-MPc hybrids are characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, ultraviolet-visible absorption and fluorescence spectroscopy. The RGO-MPc hybrids exhibit strong fluorescence quenching by means of the photo-induced electron transfer or the energy transfer (PET/ET) process between the RGO and MPc moieties. The PET/ET process particularly depends on the fluorescence quantum yield of MPc molecules with different central metals. The nonlinear optical (NLO) properties of the RGO-MPc hybrids are investigated by using the Z-scan technique at 532 nm with 4 ns laser pulses. The results show that the NLO properties of MPc molecules increase in the order of Zn < Pb < Cu, but the RGO-MPc hybrids exhibit NLO performance in the inverse sequence of Zn > Pb > Cu, implying that the NLO response arising from the efficient PET/ET process between RGO and MPc may play a more important role in the NLO properties of RGO-MPc hybrids than that originating from the MPc moiety.

Stably dispersed carbon nanotubes covalently bonded to phthalocyanine cobalt(II) for ppb-level H2S sensing at room temperature

Cost-efficient, highly sensitive and stable sensing materials play a key role in developing H2S sensors. Herein, tetra-β-carboxyphenyloxyphthalocyanine cobalt(II) (cPcCo) has been successfully bonded on the surface of acidified multiwalled carbon nanotubes (aCNTs) by a facile two-step condensation reaction in the presence of N,N′-dicyclohexylcarbodiimide (DCC), using hydroquinone (HQ), p-aminophenol (PAP), and p-phenylenediamine (PPD) as linking molecules, respectively. The obtained cPcCo–B–aCNT (B= HQ, PAP, and PPD) hybrids display good dispersibility in ethanol, which is beneficial to construct uniform sensing devices. The cPcCo–B–aCNT sensors, with a loose network-like structure, present abundant exposed sensing sites, oriented transmission of charges, and unimpeded pathways for H2S diffusion, which endow the cPcCo–B–aCNT hybrids with excellent sensing performance, in terms of sensitivity, reliability, reproducibility, and detection limit. The detection limit of the sensors composed of cPcCo–B–aCNT hybrids towards H2S reaches the ppb-level at room temperature, which is about the same as the odor threshold level for humans. For the cPcCo–HQ–aCNT sensor, the response to H2S varies linearly with respect to its concentration from 20 to 160 ppb and from 320 to 2560 ppb, with the highest gas response of 2.5% to 80 ppb H2S and a low detection limit of 5 ppb. Furthermore, the linking molecules play a critical role in the sensitivity of H2S, as evidenced from the current–voltage characteristics. The systematic study developed here provides a valid way to fabricate other high-efficient H2S sensors.

The effect of peripheral substituents attached to phthalocyanines on the third order nonlinear optical properties of graphene oxide–zinc( ii )phthalocyanine hybrids

Two kinds of graphene oxide–zinc phthalocyanine (GO–ZnPc) hybrid materials have been prepared by the covalent functionalization method. The morphologies and structures of the two kinds of GO–ZnPc hybrids are characterized by a series of methods, such as scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, ultraviolet-visible absorption and fluorescence spectroscopies. From the fluorescence spectra, the two kinds of GO–ZnPc hybrids display strong fluorescence quenching by the photo-induced electron transfer (PET) process from ZnPc moieties to the GO. Energy diagrams show that a PET process from ZnPc molecules to GO nanosheets exists. The third order nonlinear optical (NLO) properties of GO–ZnPc hybrids are investigated by the Z-scan technique at 532 nm with 4 ns laser pulses. The nonlinear absorption coefficient β value of GO–ZnPc(DG)4 is larger than that of GO–ZnPc(TD)4 because GO–ZnPc(DG)4 possesses peripheral substituents with a stronger electron-donating effect compared to GO–ZnPc(TD)4.

Enhanced NH3-Sensitivity of Reduced Graphene Oxide Modified by Tetra-α-Iso-Pentyloxymetallophthalocyanine Derivatives

Three kinds of novel hybrid materials were prepared by noncovalent functionalized reduced graphene oxide (rGO) with tetra-α-iso-pentyloxyphthalocyanine copper (CuPc), tetra-α-iso-pentyloxyphthalocyanine nickel (NiPc) and tetra-α-iso-pentyloxyphthalocyanine lead (PbPc) and characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), Raman spectra, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and atomic force microscope (AFM). The as-synthesized MPc/rGO hybrids show excellent NH3 gas-sensing performance with high response value and fast recovery time compared with bare rGO. The enhancement of the sensing response is mainly attributed to the synergism of gas adsorption of MPc to NH3 gas and conducting network of rGO with greater electron transfer efficiency. Strategies for combining the good properties of rGO and MPc derivatives will open new opportunities for preparing and designing highly efficient rGO chemiresistive gas-sensing hybrid materials for potential applications in gas sensor field.

An electrochemical bifunctional sensor for the detection of nitrite and hydrogen peroxide based on layer-by-layer multilayer films of cationic phthalocyanine cobalt(II) and carbon nanotubes

As vital biological mediators, the accurate detection of nitrite (NO2 -) and hydrogen peroxide (H2O2) is desirable for clinical monitoring and diagnosis. Herein, cationic 2,9,16,23-tetra[4-(N-methyl)pyridinyloxy]phthalocyanine cobalt(ii) ([TMPyPcCo]4+) and acid-treated multiwalled carbon nanotubes (aCNTs) were alternately self-assembled on the glassy carbon electrode (GCE) by means of the electrostatic interaction, leading to a 3D loose and interconnected assembly of [TMPyPcCo/aCNTs]n multilayer films. In the [TMPyPcCo/aCNTs]n films, [TMPyPcCo]4+ is anchored onto the surface of aCNTs without any inert polymer binders, which is beneficial to expose more active sites for electrocatalysis. The effective combination of [TMPyPcCo]4+ and aCNTs brings many advantages in electrochemical detection, involving the fast oriented transmission of charges, permeable channels for ion adsorption and transport, and more sensing sites, thus the [TMPyPcCo/aCNTs]n films display excellent electrochemical sensitivity towards both NO2 - and H2O2. The responses of NO2 - and H2O2 vary linearly with respect to the concentration from 5 µM to 30 mM and 10 µM to 9 mM. Furthermore, the superior cycling stability, reproducibility, and selectivity make [TMPyPcCo/aCNTs]n films suitable for the real samples.

Ultrafast third-order nonlinear optical properties of ZnPc(OBu)6(NCS)/DMSO solution

The ultrafast third-order nonlinear optical properties of ZnPc(OBu)(6)(NCS)/dimethyl sulfoxide solution are investigated by optical Kerr effect (OKE) and pump-probe techniques with femtosecond pulses. Using CS(2) as the reference, the third-order susceptibility of the sample solution is obtained as about 1.40x10(-14) esu at a concentration of 3.00x10(-5) M. The second hyperpolarizability for the sample solution is deduced to be as large as 2.35x10(-31) esu. The dynamic characteristics of the nonlinear optical response and the origins of the OKE signal can be attributed to excited singlet state populations.

Strong reverse saturable absorptive effect of an ultrathin film containing octacarboxylic cobalt phthalocyanine and polyethylenimine

A novel nanoscopic composite film with alternating layers consisting of anionic octacarboxylic cobalt phthalocyanine [CoPc(COONa)8] and cationic polyethylenimine (PEI) has been fabricated by an electrostatic, layer-by-layer, self-assembly technique. UV-vis spectroscopy revealed consecutive regular deposition of CoPc(COONa)8/PEI onto a quartz slide. The films delicate nanostructure was characterized by atomic force microscopy and small angle X-ray diffraction. Third-order nonlinear properties of the film performed using Z-scan measurements with 21 ps laser pulses at the incidence wavelength of 532 nm showed rather strong, nonlinear reverse saturable absorption.

Optical limiting of metallic naphthalocyanine compound

The optical limiting properties of the metallic naphthalocyanine with high transmission at visible range were studied by using a double-frequency ns/ps Nd:YAG laser system at 532 nm with pulse width of 8 ns. Influences of Br substitute on excited state absorption are significant. The effective excited state absorption model was used to describe the optical limiting effect.