The rising demand for radiation detection materials in many applications has led to extensive research on scintillators. The ability of a scintillator to absorb high-energy (kiloelectronvolt-scale) X-ray photons and convert the absorbed energy into low-energy visible photons is critical for applications in radiation exposure monitoring, security inspection, X-ray astronomy and medical radiography. However, conventional scintillators are generally synthesized by crystallization at a high temperature and their radioluminescence is difficult to tune across the visible spectrum. Here we describe experimental investigations of a series of all-inorganic perovskite nanocrystals comprising caesium and lead atoms and their response to X-ray irradiation. These nanocrystal scintillators exhibit strong X-ray absorption and intense radioluminescence at visible wavelengths. Unlike bulk inorganic scintillators, these perovskite nanomaterials are solution-processable at a relatively low temperature and can generate X-ray-induced emissions that are easily tunable across the visible spectrum by tailoring the anionic component of colloidal precursors during their synthesis. These features allow the fabrication of flexible and highly sensitive X-ray detectors with a detection limit of 13 nanograys per second, which is about 400 times lower than typical medical imaging doses. We show that these colour-tunable perovskite nanocrystal scintillators can provide a convenient visualization tool for X-ray radiography, as the associated image can be directly recorded by standard digital cameras. We also demonstrate their direct integration with commercial flat-panel imagers and their utility in examining electronic circuit boards under low-dose X-ray illumination.

Sensitive platform: The use of graphene oxide (GO) as a platform for the sensitive and selective detection of DNA and proteins is presented. The interaction of GO and dye-labeled single-stranded DNA leads to quenching of the dye fluorescence. Conversely, the presence of a target DNA or protein leads to the binding of the dye-labeled DNA and target, releasing the DNA from GO, thereby restoring the dye fluorescence (see picture).

Chemodynamic therapy (CDT) utilizes iron-initiated Fenton chemistry to destroy tumor cells by converting endogenous H O into the highly toxic hydroxyl radical ( OH). There is a paucity of Fenton-like metal-based CDT agents. Intracellular glutathione (GSH) with OH scavenging ability greatly reduces CDT efficacy. A self-reinforcing CDT nanoagent based on MnO is reported that has both Fenton-like Mn delivery and GSH depletion properties. In the presence of HCO , which is abundant in the physiological medium, Mn exerts Fenton-like activity to generate OH from H O . Upon uptake of MnO -coated mesoporous silica nanoparticles (MS@MnO NPs) by cancer cells, the MnO shell undergoes a redox reaction with GSH to form glutathione disulfide and Mn , resulting in GSH depletion-enhanced CDT. This, together with the GSH-activated MRI contrast effect and dissociation of MnO , allows MS@MnO NPs to achieve MRI-monitored chemo-chemodynamic combination therapy.

Chemodynamic therapy (CDT) employs Fenton catalysts to kill cancer cells by converting intracellular H 2 O 2 into hydroxyl radical (•OH), but endogenous H 2 O 2 is insufficient to achieve satisfactory anticancer efficacy. Despite tremendous efforts, engineering CDT agents with specific and efficient H 2 O 2 self-supplying ability remains a great challenge. Here, we report the fabrication of copper peroxide (CP) nanodot, which is the first example of a Fenton-type metal peroxide nanomaterial, and its use as an activatable agent for enhanced CDT by self-supplying H 2 O 2 . The CP nanodots were prepared through coordination of H 2 O 2 to Cu 2+ with the aid of hydroxide ion, which could be reversed by acid treatment. After endocytosis into tumor cells, acidic environment of endo/lysosomes accelerated the dissociation of CP nanodots, allowing simultaneous release of Fenton catalytic Cu 2+ and H 2 O 2 accompanied by a Fenton-type reaction between them. The resulting •OH induced lysosomal membrane permeabilization through lipid peroxidation and thus caused cell death via a lysosome-associated pathway. In addition to pH-dependent •OH generation property, CP nanodots with small particle size showed high tumor accumulation after intravenous administration, which enabled effective tumor growth inhibition with minimal side effects in vivo. Our work not only provides the first paradigm for fabricating Fenton-type metal peroxide nanomaterials, but also presents a new strategy to improve CDT efficacy.

Multifunctional nanocomposites have the potential to integrate sensing, diagnostic, and therapeutic functions into a single nanostructure. Herein, we synthesize Fe 3 O 4 @polydopamine core-shell nanocomposites (Fe 3 O 4 @PDA NCs) through an in situ self-polymerization method. Dopamine, a melanin-like mimic of mussel adhesive proteins, can self-polymerize to form surface-adherent polydopamine (PDA) films onto a wide range of materials including Fe 3 O 4 nanoparticles used here. In such nanocomposites, PDA provides a number of advantages, such as near-infrared absorption, high fluorescence quenching efficiency, and a surface for further functionalization with biomolecules. We demonstrate the ability of the Fe 3 O 4 @PDA NCs to act as theranostic agents for intracellular mRNA detection and multimodal imaging-guided photothermal * Address correspondence to hhyang@fio.org.cn, gangliu.cmitm@xmu.edu.cn.. Conflict of Interest:The authors declare no competing financial interest. Supporting Information Available:Additional information as noted in the text. This material is available free of charge via the Internet at http://pubs.acs.org. Messenger RNA (mRNA), a single-stranded ribonucleic acid, is also the blueprint for the cellular production of proteins. Moreover, some mRNAs are disease-relevant and can be utilized as markers to determine the stage of the disease. 22 Recently, several methods such as microarray analysis 23 and real-time polymerase chain reaction (RT-PCR) 24 have been developed for mRNA detection. Although these methods are effective for detecting mRNA expression in bulk samples, they are incapable of identifying cell-to-cell mutations. Significantly, many important biological processes not only are related with bulk mRNA expression, but also rely highly on cell-to-cell variations in mRNA. 25 Thus, it is necessary to develop useful approaches for detecting mRNA in living cells. [26][27][28][29][30][31][32] In this work, we fabricated multifunctional Figure 1a). Furthermore, we demonstrated that PDA can adsorb dye-labeled singlestranded DNA (ssDNA) probe and effectively quench the fluorescence of the dye. In the presence of the target, the specific binding between the dye-labeled ssDNA probe and its Figure 1c). Our results suggest a high potential for the use of PDA in the construction of multifunctional nanocomposites for simultaneous diagnosis and therapy of cancer. HHS Public Access RESULTS AND DISCUSSIONFe 3 O 4 NPs were easily coated with a uniform PDA shell by dispersing them in an alkaline DA solution and mildly shaking at room temperature for 4 h. Transmission electron microscopy (TEM) revealed that approximately a 4 nm thick PDA shell was wrapped on the surface of the Fe 3 O 4 NPs after self-polymerization of the DA ( Figure 2a). The dynamic light scattering (DLS) data showed that the hydrodynamic diameter of the Fe 3 O 4 NPs was increased after the PDA coating (Supporting Information Figure S1), which is consistent with the TEM results. Moreover, the Fe 3 O 4 @PDA NCs exhibited excelle...

Scintillators, which are capable of converting ionizing radiation into visible photons, are an integral part of medical, security, and commercial diagnostic technologies such as X-ray imaging, nuclear cameras, and computed tomography. Conventional scintillator fabrication typically involves high-temperature sintering, generating agglomerated powders or large bulk crystals, which pose major challenges for device integration and processability. On the other hand, colloidal quantum dot scintillators cannot be cast into compact solid films with the necessary thickness required for most X-ray applications. Here, we report the room-temperature synthesis of a colloidal scintillator comprising CsPbBr 3 nanosheets of large concentration (up to 150 mg/mL). The CsPbBr 3 colloid exhibits a light yield (∼21000 photons/MeV) higher than that of the commercially available Ce:LuAG single-crystal scintillator (∼18000 photons/MeV). Scintillators based on these nanosheets display both strong radioluminescence (RL) and long-term stability under X-ray illumination. Importantly, the colloidal scintillator can be readily cast into a uniform crack-free largearea film (8.5 × 8.5 cm 2 in area) with the requisite thickness for high-resolution X-ray imaging applications. We showcase prototype applications of these high-quality scintillating films as X-ray imaging screens for a cellphone panel and a standard central processing unit chip. Our radiography prototype combines large-area processability with high resolution and a strong penetration ability to sheath materials, such as resin and silicon. We reveal an energy transfer process inside those stacked nanosheet solids that is responsible for their superb scintillation performance. Our findings demonstrate a large-area solution-processed scintillator of stable and efficient RL as a promising approach for low-cost radiography and X-ray imaging applications.

Current X-ray imaging technologies involving flat-panel detectors have difficulty in imaging three-dimensional (3D) objects because fabrication of large-area, flexible silicon-based photodetectors on highly curved surfaces remains a challenge 1-3 . Here we demonstrate ultralong-lived X-ray trapping for flat-panel-free, high-resolution 3D imaging using a series of solution-processable, lanthanide-doped nanoscintillators. Corroborated with quantum mechanical simulation, our experimental characterizations show that a thermally activated slow-hopping of trapped electrons, due to radiation-induced anionic migration in host lattices, induces more than 30 days of persistent radioluminescence. We further demonstrate X-ray luminescence extension imaging (Xr-LEI) with >20-lp/mm resolution and >15-day optical memory. These findings provide insight into mechanisms underlying X-ray energy conversion through enduring electron trapping and also offer a new paradigm to motivate future research in wearable X-ray detectors for patient-centered radiography and mammogram, imaging-guided therapeutics, high-energy physics, and deep learning in radiology.

Photoacoustic (PA) imaging as a fast‐developing imaging technique has great potential in biomedical and clinical applications. It is a noninvasive imaging modality that depends on the light‐absorption coefficient of the imaged tissue and the injected PA‐imaging contrast agents. Furthermore, PA imaging provides superb contrast, super spatial resolution, and high penetrability and sensitivity to tissue functional characteristics by detecting the acoustic wave to construct PA images. In recent years, a series of PA‐imaging contrast agents are developed to improve the PA‐imaging performance in biomedical applications. Here, recent progress of PA contrast agents and their biomedical applications are outlined. PA contrast agents are classified according to their components and function, and gold nanocrystals, gold‐nanocrystal assembly, transition‐metal chalcogenides/MXene‐based nanomaterials, carbon‐based nanomaterials, other inorganic imaging agents, small organic molecules, semiconducting polymer nanoparticles, and nonlinear PA‐imaging contrast agents are discussed. The applications of PA contrast agents as biosensors (in the sensing of metal ions, pH, enzymes, temperature, hypoxia, reactive oxygen species, and reactive nitrogen species) and in bioimaging (lymph nodes, vasculature, tumors, and brain tissue) are discussed in detail. Finally, an outlook on the future research and investigation of PA‐imaging contrast agents and their significance in biomedical research is presented.