Synthesis of blue fluorescent molybdenum nanoclusters with novel terephthaldehyde-cysteine Schiff base for detection of pyrophosphate

A binuclear zinc complex (Zn2L) as ratiometric probe for the pyrophosphate (PPi) sensing

Phosphate anion (PPi) as hydrolysis products of adenosine triphosphate (ATP), is related to various biochemical reactions, particularly energy storage and transfer, nucleotide metabolism, and cellular signaling. In this paper, a binuclear zinc complex (Zn2L) was prepared for the PPi sensing in Tris-HCl solution. The results showed a clear fluorescence change from blue to green (425 nm → 500 nm) with the addition of PPi to the probe. The probe Zn2L demonstrated a remarkable selectivity for PPi in comparison to common anions, with an estimated limit of detection (LOD) of 0.29 μM within a working range of 0-9 μM. UV titration experiments showed two binding steps from 1 : 1 to 1 : 2 complex (Zn2L-PPi). Density-functional theory (DFT) studies were further conducted to find an energy gap that decreases with complex (probe + 2PPi) formation, resulting in a redshift of the absorption spectrum (360 nm → 430 nm). In addition, the Zn2L probe was also used for PPi sensing in a urine sample, in which relative standard deviation values (1.19-2.17%) and recoveries (95.00-103.00%) were obtained.

Integration of 6-Thioguanine Functionalized Molybdenum-Copper Bimetallic Nanoclusters With Fluorescence Spectroscopy for the Sensitive Detection of Uric Acid in Biofluids

In this paper, a single-step synthetic approach is presented for the development of bimetallic molybdenum-copper nanoclusters (Mo-CuNCs), shielded by a small molecule 6-thioguanine (6-TG). The Mo-CuNCs possessed a small size, high fluorescence, stable behavior, and good solubility in water. The 6-TG-Mo-CuNCs exhibit strong blue fluorescence emission at 410 nm after exciting at 330 nm as compared to its monometallic nanoclusters. Utilizing 6-TG-Mo-CuNCs superior biochemical stability, uric acid (UA) can be specifically detected as an oxidative stress biomarker using an inner filter effect mechanism. The probe demonstrated good sensing capability for detecting UA within the range of 0.09-5.00 μM and a detection limit of 0.237 μM. The method feasibility is further validated by quantifying UA in urine and plasma samples.

Ratiometric fluorescent detection of total phosphates in frozen shrimp samples using catalytic active Zr(IV) modified gold nanoclusters

Phosphate salts are important food additives in a variety of foods. In this study, the Zr(IV) modified gold nanoclusters (Au NCs) were prepared for ratiometric fluorescent sensing of phosphate additives in seafood samples. Compared with bare Au NCs, the synthesized Zr(IV)/Au NCs showed stronger orange fluorescence at 610 nm. On the other hand, the Zr(IV)/Au NCs retained the phosphatase-like activity of Zr(IV) ions and could catalyze the hydrolysis of fluorescent substrate 4-methylumbelliferyl phosphate to produce blue emission at 450 nm. The addition of phosphate salts could effectively inhibit the catalytic activity of Zr(IV)/Au NCs, resulting the fluorescence decrease at 450 nm. However, the fluorescence at 610 nm almost unchanged upon the addition of phosphates. Based on this finding, the ratiometric detection of phosphates using the fluorescence intensity ratio (I₄₅₀/I₆₁₀) was demonstrated. The method has been further applied for sensing total phosphates in frozen shrimp samples with satisfactory results.