Metal–organic gels (MOGs) emerged as an attractive luminescent soft material for electrochemiluminescence (ECL). In this work, a cathodic ECL-activated europium metal–organic gel (Eu-MOG) has been ...synthesized by a facile mixing of Eu
3+
with 4′-(4-carboxyphenyl)-2,2′:6′,2′′-terpyridine (Hcptpy) under mild conditions. The prepared Eu-MOG is highly mesoporous for co-reactant permeation to produce an ultra-stable and high-efficient ECL, based on the antenna effect of Eu
3+
coordinating with Hcptpy. Moreover, dipicolinic acid (DPA) can competitively coordinate with Eu
3+
instead of water molecules, producing an enhanced ECL signal. Therefore, an ECL enhancement assay was developed for DPA detection. There was a linear relationship between the ECL intensity and the logarithmic concentration of DPA in the 0.01–1 μM range, and the detection limit is 7.35 nM. This work displays the promising application of Eu-MOG in the ECL field, opening a broad inspection for seeking a new generation of ECL luminophores.
Graphical Abstract
Traditional DNA-based electrochemiluminescence (ECL) biosensors generally require a laborious and time-consuming process of electrode modification. Although immobilization-free homogeneous ...electrochemical approaches have been proposed, the problems of low detectable signals from indicators and high background interferences resulting from label-free sensors remain unsolved. Herein, a new type of homogeneous label-free ECL biosensor for aflatoxin B1 (AFB1) is designed based on a double-driven signal-amplifying strategy (combination of entropy-driven and nuclease-driven) and a background reduction by magnetic graphene oxide (M-GO). The target of AFB1 competitively binds the aptamer in the duplex DNA, leading to the release of the catalyst strand which would further bind the Ru(bpy)32+-Probe (Ru-Probe) absorbed in M-GO based on the principle of entropy increase. In the presence of exonuclease III, the Ru-Probe is degraded to release Ru(bpy)32+ for detection, and the catalyst strand is preserved to trigger much more Ru(bpy)32+ released. So the nuclease-driven combined with entropy-driven amplifying strategy greatly enhances the ECL signal. Moreover, the unreacted Ru-Probes adsorbed in M-GO are removed by the magnetic separation, providing the background signal was reduced as far as possible. Under the optimum conditions, the enhanced ECL signal exhibits a linear relationship with the AFB1 concentration in the range of 1 pM–100 nM with a detection limit of 20 fM. The homogeneous ECL biosensor is successfully applied to determine AFB1 in corn samples with high sensitivity and selectivity. By altering the probes employed, this type of novel ECL biosensor is promising for further determination of diverse targets which are trace contaminants in food, environment, and the disease biomarkers.
•A double-driven signal-amplifying strategy incorporated with entropy-driven and nuclease-driven was developed.•M-GO was employed as the receiver of label-free probes and reduced background signal by magnetic separation.•The homogeneous ECL biosensor was immobilization-free of DNA probes and highly sensitive.
•A modification-free homogeneous ECL aptasensor was developed for the cost-effective detection of OA.•The M-GO adsorbed and magnetically separated the free indicators to restrain the background ...signal greatly.•The DNase I assistant signal amplification afforded the aptasensor with high sensitivity and selectivity.
Homogeneous electrochemical sensing is a modification-free approach, in which the biochemical reactions occur in a homogeneous solution rather than on a limited electrode interface. Homogeneous sensing strategies are high-efficient but yet suffer from high background signals, since the free indicators can diffuse upon the electrode to generate signals. In this work, a magnetic graphene oxide (M-GO) assisted homogeneous electrochemiluminescence (ECL) aptasensor was developed for the highly sensitive detection of okadaic acid (OA). The aptamer and Ru(bpy)32+ were adsorbed in M-GO to prepare the composite ECL probe. When the OA dissociated aptamer from M-GO, Ru(bpy)32+ was proportionally released from M-GO to generate the ECL signal. With the assistance of deoxyribonuclease I (DNase I), the cyclic dissociation and degradation of aptamers induced much more free Ru(bpy)32+ for signal amplification. But the unreleased Ru(bpy)32+ were still adsorbed in M-GO and magnetically separated. So the background signal was decreased, and the sensitivity was further improved. Results showed that the ECL intensity enhanced with the increasing logarithmic concentration of OA in the range of 0.01 ∼ 10.0 ng/mL, and the limit of detection was 4 pg/mL. The aptasensor illuminates a cost-effective approach for the highly sensitive detection of marine toxins.
► Chitosan–carbon nanotubes composite was used as a platform for DNA immobilization. ► Discrimination of a synthetic copper complex to ds- and ss-DNA was obtained. ► Hybridization detection was ...performed using the copper complex as an indicator. ► Good specificity and high sensitivity were achieved on the constructed DNA biosensor.
In this paper, a new DNA hybridization detection strategy was developed based on the immobilization of capture probe DNA on a chitosan (CS)–carbon nanotubes (CNTs) composite modified glassy carbon electrode (CS–CNTs/GCE) and the use of a copper complex, Cu(bpy)(MBZ)
2(H
2O) (bpy
=
2,2′-bipyridine, MBZ
=
p-methylbenzoate), as a new redox hybridization indicator. The electrochemical characterization experiments showed that the nanocomposite film of CS–CNTs could effectively immobilize the capture probe DNA and greatly improve the electron-transfer reactions of the electroactive molecules. Electrochemical and fluorescent spectroscopic analysis revealed that the polypyridyl copper complex of Cu(bpy)(MBZ)
2(H
2O) bound to DNA via a typical intercalation mode. Surface studies further showed that the copper complex can discriminate between double-stranded and single-stranded DNA that immobilized on the surface of CS–CNTs/GCE. When being utilized as a redox indicator for the detection of hybridization for short DNA species related to phosphinothricin acetyltransferase (PAT), the indicator showed good specificity for recognizing the complementary, three-base mismatched and non-complementary DNA. Under the optimized conditions, the oxidation peak currents of the copper complex enhanced linearly with increases in the concentration of the complementary sequence in the range from 5.0
×
10
−10 to 1.0
×
10
−8
M. A detection limit of 5.0
×
10
−10
M was also obtained based on the constructed DNA biosensor.
The sensitive and reliable nanozyme-based sensor enables the detection of low concentrations of H
O
in biological microenvironments, it has potential applications as an in-situ monitoring platform ...for cellular H
O
release. The uniformly dispersed bimetallic sulfide (Zn
SnS
) nanoflowers were synthesized via a one-pot hydrothermal method and the two kinds of metal ions can serve as morphology and structure directing agents for each other in the synthetic process. The nanoparticles were utilized as nanozyme materials to fabricate a novel electrochemical sensor, and it exhibits a distinct electrochemical response towards H
O
with excellent stability and detection capability (with a minimum detection limit of 1.79 nM (S/N=3)), the excellent characteristics facilitate the precise detection of low concentrations of H
O
in biological microenvironments. Use the macrophages differentiated from leukemia THP-1 cells as a representative sensing model, the sensor was successfully utilized for real-time monitoring of the release of H
O
induced by living cells, which has significant potential applications in clinical diagnosis and cancer treatment.
A novel metal-organic framework (MOF)-based electroactive nanocomposite containing graphene fragments and HKUST-1 was synthesized via a facile one-step solvothermal method using graphene oxide (GO), ...benzene-1,3,5-tricarboxylic acid (BTC), and copper nitrate (Cu(NO
)
) as the raw materials. The morphology and structure characterization revealed that the GO could induce the transformation of HKUST-1 from octahedral structure to the hierarchical flower shape as an effective structure-directing agent. Also, it is interesting to find out that the GO was torn into small fragments to participate in the formation of HKUST-1 and then transformed into the reduction form during the solvothermal reaction process, which dramatically increased the surface area, electronic conductivity, and redox-activity of the material. Electrochemical assays showed that the synergy of graphene and HKUST-1 in the nanocomposite leaded to high electrocatalysis, fast response, and excellent selectivity toward the reduction of hydrogen peroxide (H
O
). Based on these remarkable advantages, satisfactory results were obtained when the nanocomposite was used as a sensing material for electrochemical determination of H
O
in the complex biological samples such as human serum and living Raw 264.7 cell fluids.
Electrochemiluminescence (ECL) arises from the collisional annihilation between the electro-excited luminophore and co-reactant. Most ECL-based bioassays require extensive free co-reactants that ...collide with luminophores randomly. Herein, the N,N-dimethylaniline (DMA) group was electro-grafted on the ITO electrode surface as the bottom co-reactant layer, and the vertically ordered mesoporous silica film (VMSF) was prepared as the upper layer to regulate the accessibility of Ru(bpy)32+. Thus, the dual-layer functionalized VMSF/N-ITO was newly built for the controllable ECL study. Relevant conditions, including the DMA electro-grafting, VMSF thickness, buffer concentration and pH value, were discussed to improve the ECL efficiency. Based on the VMSF/N-ITO platform, a homogeneous ECL bioassay was developed for miRNA-21 detection. The target nucleotide sequence induced the hybridization chain reaction (HCR) of probes H1 and H2 to absorb free Ru(bpy)32+ as much as possible. Residual Ru(bpy)32+ permeated the VMSF nanochannels to collide with the DMA co-reactant in producing an ECL response. There was a linear relationship between ∆ECL intensity and logarithmic concentration of miRNA-21 in the 1 fM ∼ 100 pM range, and the detection limit was 0.25 fM. The developed approach was probes immobilization-free, highly sensitive, and anti-interference, opening a new avenue for ECL-based bioassays.
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•A dual-layer VMSF/N-ITO was prepared by electro-grafting co-reactant and sequentially growth of VMSF.•ECL generated in the silica nanochannels when Ru(bpy)32+ permeated to collide with bottom co-reactant.•VMSF/N-ITO combined with HCR to develop a homogeneous ECL assay for miRNA detection.•This bioassay is probe immobilization-free, high ECL-efficient, and biomatrix anti-fouling.
High-speed circuits based on thin film transistors (TFTs) show promising potential applications in biomedical imaging and human-machine interactions. One of the critical requirements for high-speed ...electronic devices lies in high-frequency switching or amplification at low voltages, typically driven by batteries (∼3.0 V). To date, however, most electrical performances of metal oxide TFTs are measured under direct current (DC) conditions, and their dynamic switching behaviour is scarcely explored and studied systematically. Here in this work, we present low voltage-driven, high-performance TiO
thin film transistors, which can be operated at a switching speed of MHz. Our proposed TiO
TFTs demonstrated a high on-off ratio of 10
, together with a subthreshold swing (SS) of ∼150 mV Dec
averaged over four orders of magnitude, which can be further reduced below 100 mV Dec
when the temperature cools to 77 K. Additionally, the TiO
TFTs exhibit excellent gate-pulse switching at various frequencies ranging from 1.0 Hz to 1.0 MHz. We also explored the potential application of the TiO
TFTs as logic gates by constructing a resistive-loaded inverter, which shows stable operation at 10 kHz frequency and various temperatures. Thus, our results show the great potential of TiO
TFTs as a new platform for high-speed electronic applications.
High-speed circuits based on thin film transistors (TFTs) show promising potential applications in biomedical imaging and human–machine interactions. One of the critical requirements for high-speed ...electronic devices lies in high-frequency switching or amplification at low voltages, typically driven by batteries (∼3.0 V). To date, however, most electrical performances of metal oxide TFTs are measured under direct current (DC) conditions, and their dynamic switching behaviour is scarcely explored and studied systematically. Here in this work, we present low voltage-driven, high-performance TiO2 thin film transistors, which can be operated at a switching speed of MHz. Our proposed TiO2 TFTs demonstrated a high on–off ratio of 107, together with a subthreshold swing (SS) of ∼150 mV Dec−1 averaged over four orders of magnitude, which can be further reduced below 100 mV Dec−1 when the temperature cools to 77 K. Additionally, the TiO2 TFTs exhibit excellent gate-pulse switching at various frequencies ranging from 1.0 Hz to 1.0 MHz. We also explored the potential application of the TiO2 TFTs as logic gates by constructing a resistive-loaded inverter, which shows stable operation at 10 kHz frequency and various temperatures. Thus, our results show the great potential of TiO2 TFTs as a new platform for high-speed electronic applications.
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•A hollow, hydrophilicity surface molecularly imprinted materials were prepared.•Materials possess photocatalytic, reusability, and highly selectivity.•The removal contains of ...targeted adsorption, photocatalytic degradation.•Materials exhibited favorable adsorption capacity and selectivity towards SDZ.•The photodegradation of SDZ maintains 90.00 % after 6 cycles.
Novel hollow C, N-TiO2@C surface molecularly imprinted microspheres (HCNTC-SMIPs) with hydrophilicity, reusability, and selectivity were synthesized. The core–shell hollow structure yields large specific surface areas, high surface-to-volume ratios and effective diffusion rate on both inner and outer exposed surfaces. The C, N-TiO2 shell possesses high photo-catalytic decomposition capacity toward the specific pollutants. Moreover, TiO2 acts not only as a photocatalyst but also as a double cross-linker agent of molecularly imprinted to significantly reduce the molar ratio of formaldehyde. The hydrophilic surface imprinted layer provides the recognition sites and specific pore structures. The results showed that HCNTC-SMIPs possessed a high specific surface area of 305.10 m2 g−1 and a good visible light harvesting property with a bandgap of 1.67 eV. This could efficiently suppress the photoelectron-hole recombination, and thereby heightening the photocatalytic degradation of sulfadiazine (SDZ). The photodegradation efficiency of HCNTC-SMIPs can reach 99.25 % within 140 min and 90.00 % after 6 cycles. The HCNTC-SMIPs had a higher kinetic constant (0.01815 min−1) than those of HCNTC (0.00964 min−1) and TiO2 (0.00548 min−1). HCNTC-SMIPs can achieve targeted and efficient SDZ removal, as well as in-situ regeneration. The possible degradation pathways of SDZ primarily includes smiles-type rearrangement, SO2 extrusion, ring hydroxylation, direct oxidation and SN bond cleavage processes based on LC-MS analysis.
