There are many reports on long persistent phosphors (LPPs) applied in bioimaging. However, there are few reports on LPPs applied in photothermal therapy (PTT), and an integrated system with multiple functions of diagnosis and therapy. In this work, we fabricate effective multifunctional phosphors Zn3Ga2SnO8: Cr3+, Nd3+, Gd3+ with NIR persistent phosphorescence, photothermal response and magnetism. Such featured materials can act as NIR optical biolabels and magnetic resonance imaging (MRI) contrast agents for tracking the early cancer cells, but also as photothermal therapeutic agent for killing the cancer cells. This new multifunctional biomaterial is expected to open a new possibility of setting up an advanced imaging-guided therapy system featuring a high resolution for bioimaging and low side effects for the photothermal ablation of tumors.

We present a novel “Top-down” strategy to design the long phosphorescent phosphors in the second biological transparency window via energy transfer. Inherence in this approach to material design involves an ingenious engineering for hybridizing the coordination networks of hosts, tailoring the topochemical configuration of dopants and bridging a cascaded tunnel for transferring the persistent energy from traps, to sensitizers and then to acceptors. Another significance of this endeavour is to highlight a rational scheme for functionally important hosts and dopants, Cr/Nd co-doped Zn 1−x Ca x Ga 2 O 4 solid solutions. Such solid-solution is employed as an optimized host to take advantage of its characteristic trap site level to establish an electron reservoir and network parameters for the precipitation of activators Nd 3+ and Cr 3+ . The results reveal that the strategy employed here has the great potential, as well as opens new opportunities for future new-wavelength, NIR phosphorescent phosphors fabrication with many potential multifunctional bio-imaging applications.

We report a simple approach to activate the near-infrared (NIR) long persistent phosphorescence via redox reaction. NIR long persistent phosphorescence is observed in a Cr-doped non-gallate phosphor, i.e. CaTiO3: Cr with perovskite structure through heat treatment in reducing atmosphere, while no such phenomenon is observed in the sample with same composition and heat treated in air. The mechanism for activation of Cr-related long persistent phosphorescence is discussed. The designed phosphors successfully break the monopoly of the ordinary Cr3+-activated gallate phosphors with the spinel structure and provides a new route for design of long persistent phosphors.

A novel phosphor with near-infrared (NIR) long persistent luminescence, SrSnO3:Bi2+ was successfully synthesized by traditional solid-state reaction. The phosphor shows deep red-NIR persistent luminescence with a broad emission band from 700 to 900 nm peaking at 808 nm, as well as a persistence time of >30 min. This phosphor has broken the domination of conventional Cr3+, Mn2+ and Mn4+-activated long persistent phosphors and provides a new perspective on the NIR phosphorescence of Bi-doped long phosphorescent phosphors. Meanwhile, the characteristic operational waveband offer the possibility of potentially being applied in vivo bio-imaging of this new NIR phosphorescent material.

A variety of materials sintered in different atmosphere have been well investigated, but there are few reports on the long-persistent phosphorescent materials, especially the near-infrared long-persistent phosphorescent materials sintered in various atmosphere. Changing the surrounding atmosphere is an effective method to improve the afterglow properties of the materials. In this work, we fabricate a typical kind of near-infrared long-persistent phosphorescent materials of Zn3Ga2Ge2O10: 0.5% Cr(3+) in neutral, oxidizing, and reducing atmosphere. By analyzing the XRD patterns, afterglow spectra, decay and thermo-luminescence curves, we discuss the great effects on the structure, long persistent properties and trap properties of the phosphor. This work of obtaining the Zn3Ga2Ge2O10: 0.5% Cr(3+) is of great potential in the applications in night-vision surveillance and in vivo bio-imaging.

Recently, long persistent phosphors (LPPs) have been considered to be the most prominent candidates for biomedical applications. However, the LPPs suffer from a dramatic decrease in luminescence intensity after incorporation into the tissue. Therefore, it is very necessary to develop the more competitive LPPs and acquire the reproducible tissue imaging. Here, we propose and experimentally demonstrate an effective bifunctional La3Ga5GeO14: Cr3+, Nd3+ phosphor with the interesting characteristic of near-infrared long persistent phosphorescence and NIR-to-NIR Stokes luminescence. Cr3+ and Nd3+ ions are simultaneously selected as the emission centers in order to take advantage of the remarkable phosphorescence properties of Cr3+, and the appropriate energy level characteristic of NIR-excitation band (808nm) and NIR-emission (1064nm), and the ability as the brilliant auxiliary to create more efficient defects of Nd3+. The efficient dual-modal emission is, accordingly utilized to realize the convenient, high-resolution global detection and local imaging.

We present a series of efficient near-infrared (NIR) Cr3+-doped non-gallate long-persistence phosphors (Zn2SnO4: Cr and Zn(2-x)Al2xSn(1-x)O4: Cr) and highlight their special optical characteristics of broad emission band (650–1200 nm, peaking at 800 nm) and long afterglow duration (>35 h). In the context of materials selection, these systems successfully avoid the existing ubiquitous reliance on gallates as hosts in Cr3+-doped phosphorescent phosphors. Zn2SnO4 is employed as a host to take advantage of its characteristic inverse spinel crystal structure, easy substitution into Zn2+ and Sn4+ sites by Cr3+ in distorted octahedral coordination and non-equivalent substitution. In this work, Al dopant was introduced both to precisely tailor the local crystal field around the activator center, Cr3+, and to redeploy trap distribution in the system. Indeed, such redeployment permits band gap adjustment and the dynamic variation of the annihilation and the formation of defects. The results demonstrate that the method employed here can be an effective way to fabricate multi-wavelength, low-cost, NIR phosphorescent phosphors with many potential multifunctional bio-imaging applications. An international team has found a way to lower the cost and tune the emission properties of phosphorescent probes used for bioimaging. Long phosphorescent phosphors are newly developed materials that can absorb energy and release it as biologically compatible, near-infrared light over extended time frames. Typically, long phosphorescent phosphors rely on gallium ions for super-long emission, but gallium is becoming increasingly expensive. Jianrong Qiu from Guangzhou, China, and co-workers sought a cheaper alternative based on a zinc-tin oxide doped with chromium and/or aluminum atoms. The compound structure allowed the crystal field surrounding the transition metals to be easily modified through using dopants and defects; in turn, this crystal field change significantly affected the phosphorescence. Careful fabrication strategies uncovered new gallium-free phosphors that operate at multiple wavelengths and radiate for longer than 35 hours. Novel Cr3+-doped non-gallate near-infrared phosphorescent phosphor, Zn2SnO4: Cr, with the special optical characteristics of broad emission band (650–1200 nm, peaking at 800 nm) and long afterglow duration (>35 h) was presented, which successfully avoid the existing ubiquitous reliance on gallates as hosts in Cr3+-doped phosphorescent phosphors. This research also deals with the method of finely tailoring the local crystal field around the activator center, Cr3+, along with essential redeployment of trap distributions by adding Al. Indeed, such redeployment permits band gap adjustment and the dynamic variation of the annihilation and formation of defects.

Folic acid-conjugated luminescent nanomaterials have long been widely used in targeted bioimaging, often simultaneously acting as vehicles for drug delivery. They often require, however, intense light sources for photoexcitation, and this often results in photobleaching, strong luminescence background, and strong light scattering. This article describes the preparation of nanoparticles (NPs) of the type Zn1.1Ga1.8Sn0.1O4 doped with Cr(III) ions and surface-modified with folic acid. The functionalization of the NPs was monitored via measurement of zeta potentials, FTIR spectra and thermogravimetry. Cell viability and biocompatibility were tested using the MTT kit. The NPs have a size of 220 nm and were characterized by dynamic X-ray diffraction, light scattering, field emission scanning electron microscopy and high-resolution transmission electron microscopy. After annealing the NPs for 10 min at 300 °C and irradiating them with 254 nm light for 10 min, they display deep red emission that persists for up to 10 h. The NPs are easily dispersed, small-sized, and crystalline. In our perception, the new material with its long decay time offers quite novel features in terms of targeted optical imaging in providing high resolution, weak disturbance by background luminescence, and the absence of light scattering. They were successfully applied to image MCF-7 and A549 cells.