Chromophoric iridium(III) complex-coated NaYF(4): 20%Yb, 1.6%Er, 0.4%Tm nanocrystals are demonstrated as a ratiometric upconversion luminescence (UCL) probe for highly selective detection of cyanide anion and bioimaging of CN(-) in living cells through inhibition of the energy transfer from the UCL of the nanocrystals to the absorbance of the chromophoric complex. The UCL probe provides a very low detection limit of 0.18 μM CN(-) in the aqueous solution.

No abstract

Upconversion is a nonlinear optical phenomenon that involves the emission of high‐energy photons by sequential absorption of two or more low‐energy excitation photons. Due to their excellent physiochemical properties such as deep penetration depth, little damage to samples, and high chemical stability, upconversion nanoparticles (UCNPs) are extensively applied in bioimaging, biosensing, theranostic, and photochemical reactions. Here, recent achievements in the synthesis, optimization, and applications of UCNP‐based nanomaterials are reviewed. The state‐of‐the‐art approaches to synthesize UCNPs in the past few years are introduced first, followed by a summary of several strategies to optimize upconversion emissive properties and various applications of UCNPs. Lastly, the challenges and future perspectives of UCNPs are provided as a conclusion.

No abstract

Because of the extreme toxicity of cyanide anions, a great deal of effort has been invested in developing probes that use colorimetric and fluorometric methods to detect them. To date, most of the current optical probes require the use of organic solvents or a mixture of organic solvents and water. Upconversion nanophosphors (UCNPs) can serve as excellent emitters as a result of their sharp emission peaks and simple control of the emission wavelength. Here, the fabrication of hybrid material composed of iridium complex and UCNPs to detect cyanide anions selectively in pure water is described. In addition to the colorimetric detection, the upconversion luminescence emission can serve as a detection signal based on an effective luminescent resonance energy transfer (LRET) process within the hybrid nanoparticles.

Detection of Cu(2+) ions and study of their subcellular distribution in physiological processes are of considerable significance because of their potential environmental and biological applications. Some fluorescence based sensors have been developed for selective detection of Cu(2+) ions, based on organic fluorescent probes that specifically bind to Cu(2+) ions. However, these sensors are not suitable for detection in biological samples due to the short penetration depth of UV/visible light used to excite the fluorescent probes. The use of near-infrared (NIR) light can afford penetration depths of an order of magnitude greater than that of visible light, however, a material that can convert NIR light to visible light is required. A facile method has been developed for in-depth detection of Cu(2+) ions based on fluorescence upconversion. A mesoporous silica shell is coated on upconversion nanoparticles (UCNPs) and a Cu(2+) ion sensitive fluorescent probe, rhodamine B hydrazide, is incorporated into the mesoporous silica. Upon excitation by a NIR light, the UCNPs emit visible light to excite the Cu(2+)-sensitive fluorescent probe. Because of the unique optical properties of UCNPs and their ability to convert NIR light to visible light, this is a feasible method for sensitive and in-depth detection of Cu(2+) ions in a complex biological or environmental sample due to the low autofluorescence and the high penetration depth of NIR light.

No abstract

Construction of catalytic centers on natural protein aggregates is a challenging topic in biomaterial and biomedicine research. Here we report a novel construction of artificial nanoenzyme with glutathione peroxidase (GPx)-like function. By engineering the surface of tobacco mosaic virus (TMV) coat protein, the main catalytic components of GPx were fabricated on TMV protein monomers. Through direct self-assembly of the functionalized viral coat proteins, the multi-GPx centers were installed on these well-defined nanodisks or nanotubes. With the help of muti-selenoenzyme centers, the resulting organized nanoenzyme exhibited remarkable GPx activity, even approaching the level of natural GPx. The antioxidation study on subcell mitochondrial level demonstrated that virus-based nanoenzyme exerted excellent capacity for protecting cell from oxidative damage. This strategy represents a new way to develop artificial nanoenzymes.