Red-Emitting Silver Nanoclusters for Dual-Mode Detection of Cu²⁺ and Vitamin B₁₂ in Living Cells

Abstract

Biomolecule-stabilized metal nanoclusters (MNCs) exhibit enormous potential as unique luminescent materials in various applications. However, synthesis of highly stable and bio-friendly fluorescent MNCs is still a challenge. Here, we report a facile synthesis of red-emitting silver nanoclusters (LYS–AgNCs) within a dithiothreitol-reduced lysozyme (LYS) scaffold. The nanoclusters exhibit a uniform size distribution, excellent water solubility, and superior photoluminescence properties featuring a quantum yield of 6.1%, a massive (280 nm) Stokes shift, and solid-state emission, and pH stability augments their applicability in dual-mode sensing platforms for Cu2+ and vitamin B12 (VB12). Two contrasting fluorescence (FL)-quenching mechanisms are responsible for the sensing; Cu2+-induced FL quenching occurs via a multifaceted mechanism involving both static and dynamic quenching, whereas the inner filter effect and Förster resonance energy transfer are mainly responsible for VB12-induced FL quenching. An inexpensive portable paper strip is fabricated using LYS–AgNCs for on-site field application, enabling instrument-free fast and visual detection of Cu2+ and VB12. Moreover, LYS–AgNCs also possess favorable biocompatibility against human cervical cancer cells (HeLa), making them a suitable nanoprobe for cell imaging and an efficient agent for detecting Cu2+ and VB12 inside live cells as well. Finally, we demonstrate the applicability of LYS–AgNCs for real-sample analysis of VB12 with a satisfactory outcome.

Rapid Detection of Ag (I) via Size Induced Photoluminescence Quenching of Biocompatible Green Emitting L-Tryptophan Scaffolded Copper Nanocluster

“…Thus, from the MALDI-TOF analysis, it could be concluded that each tryptophan scaffolded Cu NCs were composed of less than 5 atoms. Although this result deviates from the cluster size predicted by Jellium Model [69,70], nanoclusters with a lesser number of atoms with emission in the longer wavelength are not uncommon [62,71,72].…”

Ratiometric Multimode Detection of pH and Fe3+ by Dual-Emissive Heteroatom-Doped Carbon Dots for Living Cell Applications

“…The deconvoluted XPS peaks of C 1s were at 284.4, 285.2, 286, 287.9, and 289.8 eV, which were linked to C–C/CC, C–N, CN, CO, and O–CO, respectively (Figure e). , The high-resolution N 1s spectrum revealed four different kinds of N-functionalities: pyridinic-N (398.8 eV), pyrrolic-N (399.5 eV), amino-N (400.2 eV), and graphitic-N (401.7 eV) (Figure f). , Similarly, the deconvoluted O 1s XPS spectrum exhibited well-defined peaks at 530.8, 531.3, 532.1, 533, and 533.8 eV corresponding to the O–C/C–O–C, OC–N, CO, C–OH, and O–CO bonds, respectively (Figure g). , The exact percentage of contribution calculated from the XPS analysis is presented in Table S1. The Fourier transform infrared (FTIR) spectra (Figures S1, and h) showed peaks at 1612, 1512, 1434, 1364, and 1290 to 1140 cm –1 corresponding to the stretching vibrations of the amide linkage (NH–CO), CN, CC, N–H, and C–O-related functional groups. ,,, The combined XPS and FTIR analyses ascertained the chemical composition and functionalities of the D-CD surfaces. Furthermore, the D and G bands in the Raman spectra (Figure i) were at 1371 and 1569 cm –1 , respectively, with the D/G band intensity ratio at 1.08, suggesting effective Raman active surface sites.…”

“…The Fourier transform infrared (FTIR) spectra (Figures S1, and 1h) showed peaks at 1612, 1512, 1434, 1364, and 1290 to 1140 cm −1 corresponding to the stretching vibrations of the amide linkage (NH−C�O), C�N, C�C, N−H, and C−O-related functional groups. 40,44,47,48 The combined XPS and FTIR analyses ascertained the chemical composition and functionalities of the D-CD surfaces. Furthermore, the D and G bands in the Raman spectra (Figure 1i) were at 1371 and 1569 cm −1 , respectively, with the D/G band intensity ratio at 1.08, suggesting effective Raman active surface sites.…”

Ligand engineering of luminescent AuAg nanoclusters for targeted mitochondrial and brain imaging

“…In the past few years, researchers have put tremendous effort on the design of various MNC-based luminescent probes, [31][32][33][34] such as PL-tunable ones from the visible to near infrared region in the first and second windows (NIR-I and NIR-II), 3,31 those engineered with targeted functions for specific cells/tissues/organs, 35 and those holding theranostic attributes. 36 Such a plenty of MNC-based luminescent probes substantially promoted the realization of their broad applications ranging from cell imaging, 37 disease theranostics, 38 to in vivo metabolism assessment, 39 which indeed addressed many challenging issues in the biomedical field. However, there are still several pending problems in bioimaging: (1) while many MNCs have been demonstrated to be capable in luminescence imaging of cells/tissues/organs, the advancement in subcellular organelle imaging is very slow, which is due to the lack of appropriate MNCs with targeted functions for specific subcellular organelles (e.g., mitochondria and lysosomes); (2) luminescence imaging of the brain is very challenging because it is difficult for luminescent probes to approach the brain due to the protection of the blood brain barrier (BBB).…”