Enhanced Turn-On Fluorescence Detection of Aqueous Lead Ions with Size-Shrinkable Hydrogels

A new thiacalix[4]arene-based metal-organic framework as an efficient electrochemical sensor for trace detection of Cd2+ and Pb2

Heavy metal ions (HMIs) can lead to serious harm to human health and ecological environment. Thus, developing an efficient detection method for HMIs is extremely necessary. Herein, a new thiacalix[4]arene-based metal-organic framework (MOF) [Co2(L1)(TPA)2]·DMA·3CH3OH·H2O (Co-LTPA) (L1 = thiacalix[4]arene-based ligand and H2TPA = terephthalic acid) was successfully synthesized. The electrochemical detection platform (Co-LTPA/GCE) was acquired, and Co-LTPA/GCE featured ultrasensitive detection of HMIs with greatly low limits of detection (LODs) of 0.119 nM for Cd2+ and 0.279 nM for Pb2+ as well as wide linear ranges of 0.08-5.8 μM for Cd2+ and 0.01-6.0 μM for Pb2+. More importantly, the Co-LTPA/GCE sensor was employed to detect foods (milk, honey and orange juice) and water samples (tap water, lake water and drinking water) with satisfactory recoveries, proving the sensor reliability in practical applications. This work provided an example that the functional electrochemical Co-LTPA/GCE sensor was employed for Cd2+ and Pb2+ detection.

Colorimetric-SERS dual-mode sensing of Pb(II) ions in traditional Chinese medicine samples based on carbon dots-capped gold nanoparticles as nanozyme

Peroxidase (POD)-mimicking nanozymes have got great progress in the sensing field, but most nanozyme assaying systems are built with a single-signal output mode, which is vulnerable to the effect of different factors. Thus, establishment of a dual-signal output mode is necessary for acquiring dependable and durable performance. This work described an Fe doped noradrenaline-based carbon dots and Prussian blue (Fe,NA-CDs/PB) nanocomposite as a POD-like nanozyme and modified gold nanoparticles (AuNPs) for the colorimetric and surface-enhanced Raman scattering (SERS) dual-mode sensor of Pb(II) in traditional Chinese medicine samples. With 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 3,3',5,5'-tetramethylbenzidine (TMB) as the substrates, it was found that the addition of Pb(II) inhibited the POD-like activity of Fe,NA-CDs/PB and AuNPs, so it was used for colorimetric and SERS dual-mode assays. The POD-like activity was shown to be a "ping-pong" catalytic mechanism, whereas the addition of Pb(II) produced noncompetitive inhibition with modulatory effects on Fe,NA-CDs/PB. The linear response range for colorimetric and SERS sensor detection of Pb(II) was 0.01-1.00 mg/L with the detection limit of 5 μg/L and 8 μg/L, respectively. This dual-mode detection system shows excellent selectivity. More importantly, the Pb(II) in traditional Chinese medicine samples have successfully assayed with good recovery from 90.4 to 108.9 %.

Highly fluorescent quinone-capped silver hydrosol for environmental remediation and sensing applications

A metal-enhanced fluorescence was achieved from in situ-generated Ag0 nanoparticles in the proximity of 2-hydroxy benzaldehyde (2HB). Such nanoparticles eliminated methyl blue (MB) dye from water exclusively in the presence of Zn2+ and were proven to be an efficient adsorbent for environmental remediation (maximum uptake capacity 1065 mg·g-1). Ag was zero valent in the absorbent, while Zn2+ was in Zn(OH)2 form. Fe3+ brought back MB in the aqueous medium due to the strong interaction of MB with Fe3+ and the regeneration of blue color helped to design a selective and sensitive Fe3+ sensing platform colorimetrically (linear detection range 10-4-10-6 M; linear detection limit 10-6 M). The silver nanoparticle-induced metal-enhanced fluorescence was quenched efficiently with MB. Pb2+ restored the quenched fluorescence by removing MB from the proximity of the metalized surface of silver, and Pb2+ sensing was performed fluorometrically (linear detection range; 10-5-5 × 10-8 M limit of detection 5 × 10-8 M). Iron and lead were also estimated in a variety of natural water sources, including rainfall, drinking water from taps, and water from the Ganga River via spiking method.

Competitive photoelectrochemical aptamer sensor based on a Z-scheme Fe2O3/g-C3N4 heterojunction for sensitive detection of lead ions

Lead ion (Pb2+) is one of the heavy metal contaminants within the environment, which can seriously affect biological health. Thus, it is very important to detect lead ions, especially exceeding the standard concentration (100 ng/mL). In this work, we have developed a photoelectrochemical (PEC) aptamer sensor with Z-scheme Fe2O3/g-C3N4 heterojunction as a substrate material for sensitive detection of Pb2+. Specifically, Fe2O3/g-C3N4 is employed as a substrate with a powerful and stable photocurrent response. Au and DNA-1 connected to the substrate material via the Au-S bond and increased the electron conduction. Marking DNA-2 with ZnO effectively reduced the light absorption intensity resulting in a lower photocurrent response. Surprisingly, the Pb2+ PEC sensor showed good linearity in the detection range of 62 pg/mL to 1 μg/mL with a detection limit as low as 7.9 pg/mL (S/N = 3). The sensor showed stable recovery and low relative standard deviation in real sample detection. Additionally, the sensor exhibited excellent stability, selectivity, and reproducibility. The reproducibility of the electrodes was evaluated, and the accuracy of the individual electrode current values was calculated to range from 0.5% to 2.71% with an RSD of 1.74%. Such PEC sensor guarantees to supply a brand-new approach to the detection of Pb2+.

Advance Progress on Luminescent Sensing of Nitroaromatics by Crystalline Lanthanide-Organic Complexes

Water environment pollution is becoming an increasingly serious issue due to industrial pollutants with the rapid development of modern industry. Among many pollutants, the toxic and explosive nitroaromatics are used extensively in the chemical industry, resulting in environmental pollution of soil and groundwater. Therefore, the detection of nitroaromatics is of great significance to environmental monitoring, citizen life and homeland security. Lanthanide-organic complexes with controllable structural features and excellent optical performance have been rationally designed and successfully prepared and used as lanthanide-based sensors for the detection of nitroaromatics. This review will focus on crystalline luminescent lanthanide-organic sensing materials with different dimensional structures, including the 0D discrete structure, 1D and 2D coordination polymers and the 3D framework. Large numbers of studies have shown that several nitroaromatics could be detected by crystalline lanthanide-organic-complex-based sensors, for instance, nitrobenzene (NB), nitrophenol (4-NP or 2-NP), trinitrophenol (TNP) and so on. The various fluorescence detection mechanisms were summarized and sorted out in the review, which might help researchers or readers to comprehensively understand the mechanism of the fluorescence detection of nitroaromatics and provide a theoretical basis for the rational design of new crystalline lanthanide-organic complex-based sensors.

Shrinkable Hydrogel-Enhanced Biomarker Detection with X-ray Fluorescent Nanoparticles

This paper reports a new method to enhance the sensitivity of nanoparticle-based protein detection with X-ray fluorescence by exploiting the large volume reduction of hydrogel upon dehydration. A carboxylated agarose hydrogel with uniaxial microchannels is used to allow rapid diffusion of nanoparticles and biomolecules into the hydrogel and water molecules out of the hydrogel. Carboxylated hydrogels are modified to capture protein biomarkers and X-ray fluorescence nanoparticles (iron oxide nanoparticles) are modified with antibodies that are specific to protein biomarkers. The presence of protein biomarkers in solution binds the nanoparticles on the hydrogel channels. The dehydration of hydrogels leads to a size reduction of over 80 times, which increases the number of nanoparticles in the interaction volume of the primary X-ray beam and the intensity of characteristic X-ray fluorescence signal. A detection limit of 2 μg/mL for protein detection has been established by determining the number of nanoparticles using X-ray fluorescence.