Sub-Picomolar Recognition of Cr3+ through Bioinspired Organic–Inorganic Ensemble Utilization

Facile preparation of bimetallic Au-Cu nanoclusters as fluorescent nanoprobes for sensitive detection of Cr3+ and S2O82- ions

Metallic nanoclusters (NCs) have attracted special attention from researchers due to their interesting optical properties. In this experiment, we proposed a facile one-step method for the synthesis of bimetallic gold-copper nanoclusters (AuCuNCs). The prepared AuCuNCs were characterized by fluorescence spectroscopy (FL), UV-vis absorption spectrum, transmission electron microscopy (TEM), etc. The emission peak of the prepared AuCuNCs was located at 455 nm and showed blue luminescence under the excitation of 365 nm UV light. Furthermore, after the addition of Cr³⁺ and S₂O₈^2- ions, the FL emission intensity of AuCuNCs was significantly reduced at 455 nm and there was a color change of diminished blue luminescence under UV lamp. The AuCuNCs exhibited excellent linearity and sensitivity for the detection of Cr³⁺ and S₂O₈^2- ions. The limits of detection (LOD) for the Cr³⁺ and S₂O₈^2- ions were calculated to be 1.5 and 0.037 μM, respectively. Finally, the recoveries of Cr³⁺ and S₂O₈^2- ions in Runxi Lake and tap water were measured by standard addition recovery test and were 96.66 ∼ 116.29 %, 95.75 ∼ 119.4 %.

Sensing High 17β-Estradiol Concentrations Using a Planar Microwave Sensor Integrated with a Microfluidic Channel

The global issue of pollution caused by endocrine-disrupting chemicals (EDCs) has been gaining increasing attention. Among the EDCs of environmental concern, 17β-estradiol (E2) can produce the strongest estrogenic effects when it enters the organism exogenously through various routes and has the potential to cause harm, including malfunctions of the endocrine system and development of growth and reproductive disorders in humans and animals. Additionally, in humans, supraphysiological levels of E2 have been associated with a range of E2-dependent disorders and cancers. To ensure environmental safety and prevent potential risks of E2 to human and animal health, it is crucial to develop rapid, sensitive, low cost and simple approaches for detecting E2 contamination in the environment. A planar microwave sensor for E2 sensing is presented based on the integration of a microstrip transmission line (TL) loaded with a Peano fractal geometry with a narrow slot complementary split-ring resonator (PF-NSCSRR) and a microfluidic channel. The proposed technique offers a wide linear range for detecting E2, ranging from 0.001 to 10 mM, and can achieve high sensitivity with small sample volumes and simple operation methods. The proposed microwave sensor was validated through simulations and empirical measurements within a frequency range of 0.5-3.5 GHz. The E2 solution was delivered to the sensitive area of the sensor device via a microfluidic polydimethylsiloxane (PDMS) channel with an area of 2.7 mm² and sample value of 1.37 µL and measured by a proposed sensor. The injection of E2 into the channel resulted in changes in the transmission coefficient (S₂₁) and resonance frequency (F_r), which can be used as an indicator of E₂ levels in solution. The maximum quality factor of 114.89 and the maximum sensitivity based on S₂₁ and F_r at a concentration of 0.01 mM were 1746.98 dB/mM and 40 GHz/mM, respectively. Upon comparing the proposed sensor with the original Peano fractal geometry with complementary split-ring (PF-CSRR) sensors without a narrow slot, several parameters were evaluated, including sensitivity, quality factor, operating frequency, active area, and sample volume. The results showed that the proposed sensor exhibited an increased sensitivity of 6.08% and had a 40.72% higher quality factor, while the operating frequency, active area, and sample volume showed decreases of 1.71%, 25%, and 28.27%, respectively. The materials under tests (MUTs) were analyzed and categorized into groups using principal component analysis (PCA) with a K-mean clustering algorithm. The proposed E2 sensor has a compact size and simple structure that can be easily fabricated with low-cost materials. With the small sample volume requirement, fast measurement with a wide dynamic range, and a simple protocol, this proposed sensor can also be applied to measure high E2 levels in environmental, human, and animal samples.

A novel fluorescent nanoprobe based on potassium permanganate-functionalized Ti3C2 QDs for the unique "turn-on" dual detection of Cr3+ and Hg2+ ions

Titanium carbide quantum dots (Ti₃C₂ QDs) were synthesized by ammonia-assisted hydrothermal method. We also synthesized potassium permanganate (KMnO₄)-functionalized Ti₃C₂ QDs (Mn-QDs) by modifying Ti₃C₂ nanosheets with KMnO₄ and then cutting the functional nanosheets into Mn-QDs. The Ti₃C₂ QDs and Mn-QDs were characterized by fluorescence spectroscopy (FL), Fourier transform infrared spectroscopy (FTIR), UV-vis spectrophotometry (UV-vis), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Furthermore, the modified Mn-QDs have strong luminescence ability and good dispersion stability, which can be used for Cr³⁺ and Hg²⁺ double ion detection with enhanced fluorescence specificity. Cr³⁺/Hg²⁺ and negatively charged Mn-QDs are bound together by electrostatic interactions. Meanwhile, the surface of Mn-QDs is rich in functional groups, which interacts with Cr³⁺/Hg²⁺ to modify the surface traps, leading to defect passivation and exhibiting photoluminescence enhancement. For the dynamic quenching produced by the interaction of Mn-QDs with Hg²⁺ within 50 μM, it may be caused by the complex formation of Hg²⁺ trapped by the amino group on the surface of Mn-QDs. The detection limits for Cr³⁺ and Hg²⁺ were 0.80 μM and 0.16 μM, respectively. The recoveries of Cr³⁺ and Hg²⁺ ions in real water samples were 93.79-105.10% and 93.91-102.05%, respectively, by standard addition recovery test. In this work, the application of Mn-QDs in Cr³⁺ and Hg²⁺ ion detection was researched, which opens a new way for its application in the field of detecting heavy metal ions.

Fast and Selective Detection of Cr(III) in Environmental Water Samples Using Phosphovanadate Y(V0.2P0.8O4):Eu3+ Fluorescence Nanorods

Phosphovanadate Y(V_0.2P_0.8O₄):Eu³⁺ nanorods have been created via a simple hydrothermal method and used for the highly sensitive and selective fluorescence detection of Cr³⁺ over other common heavy metal ions within a 10 min period. It was found that the fluorescence intensity of Y(V_0.2P_0.8O₄):Eu³⁺ linearly decreases with Cr³⁺ concentrations ranging from 1 × 10^-9 to 1.2 × 10^-6 M. The sensing mechanism for Cr³⁺ is ascribed to the aggregation of Y(V_0.2P_0.8O₄):Eu³⁺ nanorods triggered by Cr³⁺ ions owing to the high affinity of phosphate groups to metal ions. The excellent chemical stability, photostability over a wide pH range of 3-12, and high salt-tolerance performance with ionic strength from 1× 10^-3 to 12 M of Y(V_0.2P_0.8O₄):Eu³⁺ allow these nanorods to successfully overcome the photobleaching and pH-dependent fluorescence property of traditional organic fluorescence probes. These characteristics ensure their applicability to environmental monitoring of Cr³⁺. The sensitive determination of Cr³⁺ in different environmental water samples demonstrated the potential application of Y(V_0.2P_0.8O₄):Eu³⁺ as a practical environmental probe. With the help of a UV lamp (254 nm), the visual Cr³⁺ values for dynamic monitoring in industrial wastewater further verified that this method can even exhibit on-site visible features in daytime and night easily. This allows for the direct monitoring of environmental Cr³⁺.

A long-range emissive mega-Stokes inorganic–organic hybrid material with peripheral carboxyl functionality for As(v) recognition and its application in bioimaging

We demonstrate a strategy for the recognition of As⁵⁺ in aqueous solution using a red-emissive probe based on a perylene–Cu²⁺ ensemble decorated with peripheral free carboxyl functionality.