High-Sensitivity Sensing of Divalent Copper Ions at the Single Upconversion Nanoparticle Level

Abstract

Single-nanoparticle-level sensing allows us to measure individual molecular interactions and probe environmental stimuli at nanometer-scale resolution. Despite these premises, limited success has been met hitherto due to the demanding challenge to distinguish a dimmed signal from a noisy background. Here, we describe an approach for high-sensitivity single-nanoparticle-level sensing of divalent copper (Cu 2+ ) ions through near-infrared-to-visible upconversion luminescence against a near-null background. This nanosensor utilizes ytterbium-(Yb 3+ ) and erbium (Er 3+ )-doped sodium yttrium fluoride (NaYF 4 ) upconversion nanoparticles (UCNPs) (maximal emission at 540 nm when excited at 980 nm) as an energy donor, of which the surface attaches Cu 2+ -dependent DNAzymes labeled with BHQ1 dye (Black Hole Quencher 1, maximal absorption at 548 nm) as energy acceptors. Adding a hint amount of Cu 2+ ions resulted in the cleavage of a BHQ1-containing moiety in DNAzymes, thus turning on upconversion luminescence for sensitive detection. Indeed, this approach allows us to perform single-nanoparticle-level detection of Cu 2+ ions with extraordinary signal-to-noise ratios (SNRs, >277) for all measured concentrations that cover 3 orders of magnitude (from sub-nM to μM). Importantly, a limit of detection of 220 pM was achieved, about sevenfold lower than the one at the ensemble level. Moreover, a stochastic particle-to-particle sensing behavior was also identified, featuring single-nanoparticle-level detection. This work untaps the usage of UCNPs for high-sensitivity single-nanoparticle-level biosensing.

Intercalate Superconductivity and van der Waals Equation

“…Usually this is not the case. For example, for copper and oxygen, the former is often treated as either a divalent or monovalent element, , and the latter is typically framed as a “hole dopant” . Neither of these scenarios were considered when employing the ideal gas law at the onset or when using the van der Waals equation to estimate the gap (summarized in Figure ).…”

A Highly Sensitive Luminescent Upconversion Nanosensor for Turn-On Detection of As3+

“…Interestingly, the use of Ln 3+ -doped upconversion nanoparticles (UCNPs) as a fluorometric sensor, − which converts near-IR (NIR) radiation to visible light, provides an alternative method for As 3+ monitoring due to its outstanding features: (i) high photo/thermal stability, (ii) narrow emission band, (iii) large Stokes shifts, (iv) low phototoxicity, (v) a NIR excitation source, which offers a substantially deeper light penetration ability than UV excitation, (vi) reduced photodamage effects, and (vii) NIR-excitation features of nonblinking and nonautofluorescence assays, resulting in significant enhancement of signal-to-noise (S/N) ratios. These benefits make the UCNPs attractive particularly in sensing; however, most sensing is mainly based on fluorescence quenching induced by luminescence resonance energy transfer (LRET).…”

Fluorescence and Colorimetric Dual-Mode Ratiometric Sensor Based on Zr–Tetraphenylporphyrin Tetrasulfonic Acid Hydrate Metal–Organic Frameworks for Visual Detection of Copper Ions

“…Over the past decades, many conventional Cu 2+ detection technologies have been established, including inductively coupled plasma mass spectroscopy (ICP-MS), atomic absorption spectroscopy (AAS), surface-enhanced Raman spectroscopy (SERS), fluorescence (FL) spectrometry, − electrochemical methods, − and colorimetric sensors. − Thereinto, fluorescence and colorimetric analysis methods have attracted the attention of many researchers due to their high sensitivity, selectivity, and simple operation. Very recently, several groups have reported a series of single-emission fluorescent probes for Cu 2+ .…”