26 research outputs found
Electrochemical Functionalization of <i>N</i>‑Methyl-2-pyrrolidone-Exfoliated Graphene Nanosheets as Highly Sensitive Analytical Platform for Phenols
Graphene
nanosheets (GS) were easily prepared from graphite via a one-step
ultrasonic exfoliation approach using <i>N</i>-methyl-2-pyrrolidone
(NMP) as the solvent. Compared with the widely used graphene oxide
(GO) obtained by multistep chemical oxidation, the NMP-exfoliated
GS exhibited apparently better electrochemical activity toward the
oxidation of a series of phenols like hydroquinone, catechol, 4-chlorophenol,
and 4-nitrophenol. Interestingly, the electrochemical activity of
GS toward these phenols can be further enhanced by simply anodizing
at 1.8 V for 2 min (denoted as EGS), reflected by the apparently enlarged
oxidation peak currents in voltammograms and the obviously reduced
charge transfer resistance in electrochemical impedance spectra (EIS).
Characterizations by techniques like X-ray photoelectron spectra (XPS),
Raman spectra, and atomic force microscopy (AFM) demonstrated that
the introduction of new oxygen-containing groups or edge-plane defects
and the enhanced surface roughness were responsible for the enhanced
activity of EGS. Thereafter, a simple electrochemical method for the
highly sensitive detection of phenols was established and the detection
limits were 0.012 μM, 0.015 μM, 0.01 μM, and 0.04
μM for hydroquinone, catechol, 4-chlorophenol, and 4-nitrophenol,
respectively. The facile synthesis of EGS, together with its high
electrochemical activity, thus created a novel platform for developing
highly sensitive electrochemical sensing systems
Mesoporous-TiO2 nanoparticles based carbon paste electrodes exhibit enhanced electrochemical sensitivity for phenols
Mesoporous-TiO2 nanoparticles (meso-TiO2) and nano-TiO2 particles (nano-TiO2) were synthesized and characterized using scanning electron microscopy. The electrochemical behaviours of carbon paste electrodes (CPE), nano-TiO2/CPE and meso-TiO2/CPE were investigated using K3[Fe(CN)6] as the electrochemical probe. It was observed that the peak potential separation was remarkably decreased at the meso-TiO2/CPE with higher peak currents in comparison with the other two CPEs. Moreover, the electrochemical performance towards phenol and p-substituted phenol detection was studied with remarkably enhanced oxidation signals at meso-TiO2/CPE. The meso-TiO2 shows considerable surface enhancement effects towards phenols which increase linearly with Hammett’s constants. Additionally at higher NaCl concentrations, the oxidation peak currents of phenols notably increases at meso-TiO2/CPE, while remaining unchanged at CPE and nano-TiO2/CPE. In summary meso-TiO2 nanoparticles are superior electrode materials for electrocatalysis
Portable, Self-Powered, and Light-Addressable Photoelectrochemical Sensing Platforms Using pH Meter Readouts for High-Throughput Screening of Thrombin Inhibitor Drugs
In
this work, a self-powered, portable, and light-addressable photoelectrochemical
sensor (P-LAPECS) is developed for efficient drug screening using
a handheld pH meter readout. The sensor, which employs thrombin inhibitors
as the drug model, is constructed by evenly immobilizing biotin-labeled
and thrombin-cleavable peptides on eight separated sensing zones of
a single gold film electrode. The incubation of each peptide sensing
zone with thrombin leads to the reduction of binding sites for streptavidin-labeled
fullerene (C<sub>60</sub>) PEC bioprobes, which directly reflects
the activity of thrombin by the variation of both photocurrent and
photovoltage, and therefore allows the screening of thrombin inhibitors
using either a single-channel electrochemical analyzer or a portable
pH meter. Consequenty, the inhibition efficiency evaluation of multiple
thrombin inhibitors can be achieved by just one electrode, and the
screening result obtained by the pH meter is very close to that acquired
by the electrochemical analyzer. Moreover, P-LAPECS can realize the
light-addressable detection of thrombin with a detection limit as
low as 0.05 pM. The present work thus demonstrates the possibility
of constructing portable, inexpensive, sensitive, and high-throughput
biosensing platforms using ubiquitous pH meters for laboratories all
over the world
4‑Amino-1-(3-mercapto-propyl)-pyridine Hexafluorophosphate Ionic Liquid Functionalized Gold Nanoparticles for IgG Immunosensing Enhancement
A novel
ionic liquid, 4-amino-1-(3-mercapto-propyl)-pyridine hexafluorophosphate
(AMPPH), was successfully synthesized and characterized. Subsequently,
AMPPH was used as a functional monomer to fabricate AMPPH-modified
gold nanoparticles (AMPPH–AuNPs) via a one-pot synthesis method.
The as-prepared AMPPH–AuNPs were confirmed with transmission
electron microscopy and X-ray photoelectron spectroscopy. AMPPH–AuNPs
were used to construct a biocompatible interface to immobilize rabbit
anti-human IgG (anti-HIgG) onto a glassy carbon electrode (GCE) surface,
followed by a cross-linking step with glutaraldehyde to fabricate
an anti-HIgG–AMPPH–AuNPs/GCE. The nonspecific binding
sites were enclosed with bovine serum albumin (BSA) to develop an
immunosensor for human IgG. Electrochemical impedance spectroscopy,
cyclic voltammetry and differential pulse voltammetry were used to
investigate the electrochemical properties of the developed immunosensor.
The results indicate that AMPPH–AuNPs can improve the immunosensing
performance. The current response of the immunosensor was found linearly
related to human IgG concentration in the range of 0.1–5.0
ng mL<sup>–1</sup> and 5.0–100.0 ng mL<sup>–1</sup>. The detection limit is estimated to be 0.08 ng mL<sup>–1</sup> (<i>S</i>/<i>N</i> = 3). The obtained immunosensor
was successfully applied to the analysis human IgG immunoglobulin
in human serum, and the results were well consistent with ELISA method
White-Light-Exciting, Layer-by-Layer-Assembled ZnCdHgSe Quantum Dots/Polymerized Ionic Liquid Hybrid Film for Highly Sensitive Photoelectrochemical Immunosensing of Neuron Specific Enolase
ZnCdHgSe quantum dots (QDs) functionalized
with <i>N</i>-acetyl-l-cysteine were synthesized
and characterized. Through
layer-by-layer assembling, the ZnCdHgSe QDs was integrated with a
polymerized 1-decyl-3-[3-pyrrole-1-yl-propyl]Âimidazolium tetrafluoroborate
(PDPIT) ionic liquid film modified indium tin oxide (ITO) electrode
to fabricated a photoelectrochemical interface for the immobilization
of rabbit antihuman neuron specific enolase (anti-NSE). After being
treated with glutaraldehyde vapor and bovine serum albumin successively,
an anti-NSE/ZnCdHgSe QDs/PDPIT/ITO sensing platform was established.
Simplely using a white-light LED as an excitation source, the immunoassay
of neuron specific enolase (NSE) was achieved through monitoring the
photocurrent variation. The polymerized ionic liquid film was demonstrated
to be an important element to enhance the photocurrent response of
ZnCdHgSe QDs. The anti-NSE/ZnCdHgSe QDs/PDPIT/ITO based immunosensor
presents excellent performances in neuron specific enolase determination.
The photocurrent variation before and after being interacted with
NSE exhibits a good linear relationship with the logarithm of its
concentration (log <i>c</i><sub>NSE</sub>) in the range
from 1.0 pg mL<sup>–1</sup> to 100 ng mL<sup>–1</sup>. The limit of detection of this immunosensor is able to reach 0.2
pg mL<sup>–1</sup> (<i>S</i>/<i>N</i> =
3). The determination of NSE in clinical human sera was also demonstrated
using anti-NSE/ZnCdHgSe QDs/PDPIT/ITO electrode. The results were
found comparable with those obtained by using enzyme-linked immunosorbent
assay method