A Novel Terahertz Metamaterial Microfluidic Sensing Chip for Ultra-Sensitive Detection.

A terahertz metamaterial microfluidic sensing chip for ultrasensitive detection is proposed to investigate the response of substances to terahertz radiation in liquid environments and enhance the molecular fingerprinting of trace substances. The structure consists of a cover layer, a metal microstructure, a microfluidic channel, a metal reflective layer, and a buffer layer from top to bottom, respectively. The simulation results show that there are three obvious resonance absorption peaks in the range of 1.5-3.0 THz and the absorption intensities are all above 90%. Among them, the absorption intensity at M1 = 1.971 THz is 99.99%, which is close to the perfect absorption, and its refractive index sensitivity and Q-factor are 859 GHz/RIU and 23, respectively, showing excellent sensing characteristics. In addition, impedance matching and equivalent circuit theory are introduced in this paper to further analyze the physical mechanism of the sensor. Finally, we perform numerical simulations using refractive index data of normal and cancer cells, and the results show that the sensor can distinguish different types of cells well. The chip can reduce the sample pretreatment time as well as enhance the interaction between terahertz waves and matter, which can be used for early disease screening and food quality and safety detection in the future.

A label-free photoelectrochemical biosensor for silver ions based on Zn-Co doped C and CdS QD nanomaterials.

A sensitive photoelectrochemical (PEC) biosensor for silver ions (Ag+) was developed based on Zn-Co doped C and CdS quantum dot (CdS QD) nanomaterials. Hydrophobic modified sodium alginate (HMA), which could stabilize and improve the PEC performance of CdS QDs, was also used for the construction of PEC sensors. Especially, Zn-Co doped C, CdS QDs and HMA were sequentially modified onto an electrode surface via the drop-coating method, and a C base rich DNA strand was then immobilized onto the modified electrode. As the C base in DNA specifically recognized Ag+, it formed a C-Ag+-C complex in the presence of Ag+, which created a spatial steric hindrance, resulting in a reduced PEC response. The sensing platform is sensitive to Ag+ in the range of 10.0 fM to 0.10 µM, with a limit of detection of 3.99 fM. This work offers an ideal platform to determine trace heavy metal ions in environmental monitoring and bioanalysis.

Sensitive dual-mode sensing platform for Amyloid ß detection: Combining dual Z-scheme heterojunction enhanced photoelectrochemistry analysis and dual-wavelength ratiometric electrochemiluminescence strategy.

As a tumor biomarker, the accumulation of amyloid ß oligomers (Aßo) in the brain has been suggested as a key feature in the pathogenesis and progression of Alzheimer's disease (AD). In this work, we designed a novel photoelectrochemical (PEC) and electrochemiluminescence resonance energy transfer (ECL-RET) dual-mode biosensor to achieve ultra-sensitive detection of Aßo. Specifically, the electrode surface modified Carbon Dots (C Dots) and the electrodeposited polyaniline (PANI) film formed a Z-scheme heterojunction reversing the photocurrent signal, and then the Aßo specific recognition peptide was attached to the surface via amide bonding between the amino group of PANI and carbonyl group of peptide. After that, in the presence of CdTe labeled specific recognition aptamer for Aß (CdTe-Apt), Aßo was captured to construct a sandwich-type biosensor and exhibited a significantly enhanced cathodic photocurrent response because the formed dual Z-scheme heterojunction promoted charge separation efficiency. Interestingly, the proposed biosensor also caused a ratiometric change in the ECL intensity at 555 nm and 640 nm. Therefore, the developed biosensor achieved dual-mode detection of Aßo, where the PEC detection range of Aßo was from 10 fM to 0.1 µM (with a detection limit of 4.27 fM) and the ECL method provided a linear detection range of 10 fM to 10 nM (with a detection limit of 6.41 fM). The stability and reliability of the experimental results indicate that this has been a promising biosensing pattern and could be extended to the analysis of other biomarkers.

Photoelectrochemical sensor for detection Hg2+ based on in situ generated MOFs-like structures.

Trace analysis of mercury ions (Hg2+) is of great significance to human health and environmental protection. In this work, a novel photoelectrochemical (PEC) biosensor was developed for the ultrasensitive detection of Hg2+ based on the MOFs-like composite/CdS quantum dots (QDs) as photoactive substrate materials. The MOFs-like composite in situ formed by hydrophobically modified alginate (HMA) with europium ion (Eu3+) not only offered a friendly platform for bioconjugation but also resulted in enhancing sensor photocurrent response. Furthermore, the immobilized thymidine-rich probe DNA on the MOFs-like composite surface was bent to produce a T-Hg2+-T structure in the presence of Hg2+, resulting in enlarged steric hindrance on the electrode surface and decreased the proposed biosensor PEC response. This proposed photoelectrochemical sensing system displayed selective detection of Hg2+ with a linear range from 0.1 pM to 1.0 µM with a detection limit of 0.067 pM. The utilization of semiconductor quantum dots as light-harvesting components and the MOFs-like composite as sensitizers broadens the possible design ideas for photoelectrochemical sensing systems.

Black phosphorous quantum dots for signal-on cathodic photoelectrochemical aptasensor monoitoring amyloid ß peptide.

In this paper, a quantitative cathodic photoelectrochemical aptasensor is described by using black phosphorous quantum dots (BPQDs) as photoactive material and assisted by heme as electron acceptor for sensing of amyloid ß peptide (Aß). Specifically, BPQDs were synthesized by solvothermal method and characterized by various techniques. The as-prepared BPQDs were assembled on the transparent indium tin oxide electrode, and the positively charged poly-l-lysine (PLL) was then absorbed onto BPQDs via electronic interaction. Subsequently, the aptamer as the specific recognition element for Aß oligomer was introduced on the BPQDs-PLL modified electrode. After bound with heme to form Aß-heme complex, Aß oligomer was simultaneously captured by the aptamer on the electrode, resulting in an enhanced photocurrent response. Under the optimized conditions, the present PEC sensor reveals a good linear response to Aß peptide ranging from 1.0 fM to 100 nM with a detection limit of 0.87 fM. The present signal-on cathodic PEC bioassay possesses the potential to create a new paradigm in amplified PEC assays that could provide outstanding performance for bioanalysis.

Sodium Alginate Micelle-Encapsulating Zinc Phthalocyanine Dye-Sensitized Photoelectrochemical Biosensor with CdS as the Photoelectric Material for Hg2+ Detection.

A simple and selective photoelectrochemical (PEC) biosensor was constructed for Hg2+ detection based on zinc phthalocyanine (ZnPc) dye-sensitized CdS using alginate not only as a carrier but also as a binder. First, CdS as a photoactive material was in situ modified on the electrode surface using a rapid and simple electrodeposition to obtain an initial photocurrent signal. Second, ZnPc was loaded in the amphiphilic alginate micelle and then was coated onto the CdS film surface via alginate as the binder. The photocurrent was subsequently enhanced due to the favorable dye sensitization effect of ZnPc to CdS. Finally, the thymine-rich probe DNA was immobilized on the modified ITO surface via coupling reaction between the carbonyl groups of the amphiphilic polymer and the amino groups of the probe DNA. In the presence of Hg2+, the thymine-Hg2+-thymine (T-Hg2+-T) structure was formed due to the specific bond of Hg2+ with thymine, resulting in the decrease of photocurrent due to the increase of steric hindrance on the modified electrode surface. The proposed PEC biosensor for Hg2+ detection possessed a wide linear range from 10 pM to 1.0 µM with a detection limit of 5.7 pM. This biosensor provides a promising platform for detecting other biomolecules of interest.

[Adsorption Characteristics of Biochar on Heavy Metals (Pb and Zn) in Soil].

Three types of biochars, poplar branch biochar (PBC), water hyacinth biochar (WHC), and corn straw biochar (CSC), were prepared in a fixed-bed pyrolyzer at different pyrolysis temperatures (300-700℃). The effects of biochar species, pyrolysis temperature, and biochar addition on adsorption characteristics of typical heavy metals (HMs) such as Pb and Zn in vegetable soil (collected from a lead-zinc-silver mining area, Nanjing, China) were investigated. The adsorption mechanism of biochar on HMs was discussed based on the analyses of pore structure, XRD, and FTIR of biochars. WHC biochar showed the best adsorption ability at the same experimental conditions with adsorption efficiencies on Zn and Pb of 21.83% and 44.57%, respectively. The relative adsorption capacities of Zn and Pb were 227.65 µg·g-1 and 363.76 µg·g-1 at the pyrolysis temperature of 500℃ and biochar addition of 5%. The adsorption efficiency of biochar on HMs in soil increased gradually with increasing pyrolysis temperature. WHC biochars prepared at 500℃ and 700℃ had similar adsorption capacities on Zn and Pb in soil indicating that the moderate pyrolysis may be a good choice for WHC with better physicochemical properties. Increasing the amount of WHC addition benefits the adsorption efficiency of HMs in soil, but does not increase the adsorption capacity. The adsorption efficiency of Pb in soil reaches 93.93% by adding 10% of WHC into the soil sample. The combined analyses based on the physicochemical properties of biochar and the results of soil HMs adsorption experiments suggest that ion exchange and complexation are prevailing mechanisms of the remediation of HM-contaminated soil by WHC biochars.