Yuanqiang Hao

Simultaneous determination of dopamine and ascorbic acid using β-cyclodextrin/Au nanoparticles/graphene-modified electrodes

A sensitive electrochemical platform was fabricated based on a nanocomposite for the simultaneous electrochemical detection of dopamine (DA) and ascorbic acid (AA). The electrodeposition of Au nanoparticles (AuNPs) was performed on an electrochemically reduced graphene oxide (EDGO)-modified glass carbon electrode (GCE). The modified electrode was further functionalized with mercapto-β-cyclodextrin (HS-β-CD), which produced the β-CD/AuNPs/EDGO modified electrode. The electrochemical behaviors of DA and AA were investigated by cyclic voltammetry on the surface of β-CD/AuNPs/EDGO-modified electrodes. The separation of oxidation peak potentials for AA and DA was about 182 mV, which allowed simultaneous determination of AA and DA. Differential pulse voltammetry was used for determining AA and DA in their mixture at the β-CD/AuNPs/EDGO-modified electrode. Under optimum conditions, the linear response ranges for determination of AA and DA were 50–900 μM and 0.5–120.0 μM, with detection limits (S/N = 3) of 2 μM and 0.024 μM, respectively. Good stability and high resistance to interference were further demonstrated for the as-prepared electrochemical sensor.

Turn-on fluorescence detection of ciprofloxacin in tablets based on lanthanide coordination polymer nanoparticles

Metal–organic coordination polymers (MOCPs) have emerged as a new family of functional nanomaterials. Here, we report a facile and effective fluorescence method for detecting CIP in tablets using a kind of lanthanide coordination polymer nanoparticle (LCPNP), specifically Eu/GMP NPs, as the sensing platform. Eu/GMP NPs, composed of guanosine monophosphate (GMP) and europium (Eu3+) ion, are by themselves non-luminescent. The addition of ciprofloxacin (CIP) into the Eu/GMP NPs, however, noticeably enhanced their fluorescence due to the strong coordination interaction between CIP and Eu3+, and the improved hydrophobic interior of the LCPNPs resulted in an efficient energy transfer from CIP to Eu3+. The fluorescence intensity of Eu/GMP at 615 nm showed a linear relationship with CIP concentration between 1.0 and 40 μM, with a detection limit of 780 nM. We believe that the proposed time-resolved fluorometric assay based on the Eu/GMP NP lanthanide nanosensor, with its long fluorescence lifetime, has a great potential for using in the testing of biosamples.

A highly selective long-wavelength fluorescent probe for hydrazine and its application in living cell imaging

A highly selective long-wavelength turn-on fluorescent probe has been developed for the detection of N2H4. The probe was prepared by conjugation the tricyanofuran-based D-π-A system with a recognizing moiety of acetyl group. In the presence of N2H4, the probe can be effectively hydrazinolysized and produce a turn-on fluorescent emission at 610nm as well as a large red-shift in the absorption spectrum corresponding to a color change from yellow to blue. The sensing mechanism was confirmed by HPLC, MS, UV-vis, emission spectroscopic and theoretical calculation studies. The probe displayed high selectivity and sensitivity for N2H4 with a LOD (limit of detection) of 0.16μM. Moreover, the probe was successfully utilized for the detection of hydrazine in living cells.

Oriented growth of cross-linked metal-organic framework film on graphene surface for non-enzymatic electrochemical sensor of hydrogen peroxide in disinfectant

High-density and cross-linked copper-based metal-organic framework (Cu-MOF) sheets were successfully prepared via a simple oriented growth method on a carboxylated graphene-modified electrode surface. Hydrogen peroxide (H2O2) was selected as a model molecule to examine the performance of the thin film of Cu-MOF/graphene. The proposed sensor showed an extended linear detection range from 2.00 × 10-7 to 1.85 × 10-4 mol L-1 (R = 0.998), a high sensitivity of 0.792 A (mol L-1)-1, and a low detection limit of 6.7 × 10-8 mol L-1, due to the synergistic catalysis from the porous structure and favorable electron transfer mediating function of the electroactive Cu-MOFs and the high conductive property of the graphene. The reduction peak current of H2O2 changed less than 3.7% in the presence of 57-fold high concentrations (2.0 × 10-4 mol L-1) of the potential interfering species. The good selectivity of the prepared modified electrode was acquired by the size exclusion (molecular sieving) for H2O2 because of the proper pore shape and pore size of Cu-MOFs. The feasibility of the assay was verified by test of H2O2 in disinfectant samples. The proposed strategy presents valuable information related to the construction of non-enzymatic electrochemical sensors.

A highly selective and ratiometric fluorescent probe for cyanide by rationally altering the susceptible H-atom

A highly selective and ratiometric fluorescent probe for cyanide was rationally designed and synthesized. The probe comprises a fluorophore unit of naphthalimide and a CN- acceptor of methylated trifluoroacetamide group. For these previous reported trifluoroacetamide derivative-based cyanide chemosensors, the H-atom of amide adjacent to trifluoroacetyl group is susceptible to be attacked by various anions (CN- itself, F-, AcO-, et al.) and even the solvent molecule, which resulted in the bewildered reaction mechanism and poor selectivity of the assay. In this work, the susceptible H-atom of trifluoroacetamide was artfully substituted by alkyl group. Thus a highly specific fluorescent probe was developed for cyanide sensing. Upon the nucleophilic addition of cyanide anion to the carbonyl of trifluoroacetamide moiety of the probe, the ICT process of the probe was significantly enhanced and leading to a remarkable red shift in both absorption and emission spectra of the probe. This fluorescent assay showed a linear range of 1.0-80.0µM and a LOD (limit of detection) of 0.23µM. All the investigated interference have no influence on the sensing behavior of the probe toward cyanide. Moreover, by coating on TLC plate, the probe can be utilized for practical detection of trace cyanide in water samples.

A benzothiazole-based fluorescent probe for hypochlorous acid detection and imaging in living cells

A benzothiazole-based turn-on fluorescent probe with a large Stokes shift (190nm) has been developed for hypochlorous acid detection. The probe displays prompt fluorescence response for HClO with excellent selectivity over other reactive oxygen species as well as a low detection limit of 0.08μM. The sensing mechanism involves the HClO-induced specific oxidation of oxime moiety of the probe to nitrile oxide, which was confirmed by HPLC-MS technique. Furthermore, imaging studies demonstrated that the probe is cell permeable and can be applied to detect HClO in living cells.

A sensitive gold nanoparticle-based aptasensor for colorimetric detection of Aβ1–40 oligomers

In this work, a gold nanoparticle-based label-free homogeneous phase colorimetric bioassay was developed for the detection of Aβ1–40 oligomers (AβO), important biomarkers for diagnosis and monitoring progression of Alzheimers disease (AD). The prepared AβO-aptamer decorated AuNPs tended to aggregate in a solution with high concentrations of salt, and displayed a purple color with a maximum absorption peak at 650 nm, a characteristic absorption of aggregated AuNPs. In the presence of AβO, the specific binding of the target with the aptamer generated folded aptamer structures, which can stabilize AuNPs towards the salt-induced aggregation more effectively than AuNPs stabilized by the aptamer alone, and thus achieved a hypsochromic shift in the absorption spectra. On the basis of this sensitive spectral transformation, the proposed aptasensor was successfully applied for the detection of AβO with a dynamic range of 1–600 nM and a low detection limit of 0.56 nM. The reliability and practicality of this aptasensor was demonstrated by analysis of AβO in artificial cerebrospinal fluid (aCSF). We anticipate that the proposed facile colorimetric assay for AβO will provide applicable information for early diagnosis of AD.

Recent progress in the development of fluorescent probes for hydrazine

Hydrazine (N2 H4 ) is an important and commonly used chemical reagent for the preparation of textile dyes, pharmaceuticals, pesticides and so on. Despite its widespread industrial applications, hydrazine is highly toxic and exposure to this chemical can cause many symptoms and severe damage to the liver, kidneys, and central nervous system. As a consequence, many efforts have been devoted to the development of fluorescent probes for the selective sensing and/or imaging of N2 H4 . Although great efforts have been devoted in this area, the large number of important recent studies have not yet been systematically discussed in a review format so far. In this review, we have summarized the recently reported fluorescent N2 H4 probes, which are classified into several categories on the basis of the recognition moieties. Moreover, the sensing mechanism and probes designing strategy are also comprehensively discussed on aspects of the unique chemical characteristics of N2 H4 and the structures and spectral properties of fluorophores.

Lanthanide Functionalized Metal-Organic Coordination Polymer: Toward Novel Turn-on Fluorescent Sensing of Amyloid β-Peptide

Metal-organic coordination polymers (MOCPs) have been emerging as very attractive nanomaterials due to their tunable nature and diverse applications. Herein, using Tb3+ as the luminescence center, 1,3,5-benzenetricarboxylate (BTC) as building block and Cu2+ as the signal modulator as well as a recognition unit, we propose a novel and effective lanthanide functionalized MOCP (LMOCP) fluorescent sensor (Cu-BTC/Tb) for amyloid β-peptide (Aβ) monomer, a biomarker for Alzheimer disease (AD). Specifically, Cu-BTC/Tb, created by postsynthesis modification strategy under room temperature, is almost nonemissive due to the quenching effect of Cu2+ in the MOCP, exhilaratingly, the presence of Aβ1-40 triggered a significant emission enhancement of Cu-BTC/Tb assay due to the high binding affinity of Aβ1-40 for Cu2+ and the subsequent suppression of the quenching effect. In the assay, this LMOCP sensor shows high sensitivity with detection limit of 0.3 nM. Due to its capability to eliminate autofluorescence, Cu-BTC/Tb was also applied to the time-gated detection of Aβ1-40 in human plasma with promising results. This work presents a novel strategy for the construction of functional luminescent LMOCP for sensitively turn-on fluorescent sensing of Aβ1-40. We believe the proposed strategy would inspire the development of various LMOCP-based fluorescent assays or medical imaging platforms for advanced biological implementations.