Enhancement of upconversion luminescence of Er and Yb co-doped Y2O3 nanoparticle by Ag half-shell

Upconversion photoluminescence (PL) properties of single Y₂O₃ nanoparticles doped with Yb and Er (Y₂O₃:Yb,Er) with a Ag over-layer is studied. We traced the PL and light scattering images of individual nanoparticles by changing the thickness of a Ag over-layer. When the Ag thickness is relatively small and only the upper part of a nanoparticle is covered by Ag (Ag half-shell), the PL is strongly enhanced. On the other hand, when the Ag thickness is increased and a continuous Ag over layer is formed, the enhancement factor decreases. From the correlation between the enhancement factors of the upconversion PL and scattering intensities as well as the change of the PL lifetime, the mechanism of the PL enhancement is discussed.     

Ultralong Phosphorescence of Water‐Soluble Organic Nanoparticles for In Vivo Afterglow Imaging

Afterglow or persistent luminescence eliminates the need for light excitation and thus circumvents the issue of autofluorescence, holding promise for molecular imaging. However, current persistent luminescence agents are rare and limited to inorganic nanoparticles. This study reports the design principle, synthesis, and proof‐of‐concept application of organic semiconducting nanoparticles (OSNs) with ultralong phosphorescence for in vivo afterglow imaging. The design principle leverages the formation of aggregates through a top‐down nanoparticle formulation to greatly stabilize the triplet excited states of a phosphorescent molecule. This prolongs the particle luminesce to the timescale that can be detected by the commercial whole‐animal imaging system after removal of external light source. Such ultralong phosphorescent of OSNs is inert to oxygen and can be repeatedly activated, permitting imaging of lymph nodes in living mice with a high signal‐to‐noise ratio. This study not only introduces the first category of water‐soluble ultralong phosphorescence organic nanoparticles but also reveals a universal design principle to prolong the lifetime of phosphorescent molecules to the level that can be effective for molecular imaging.     

In Vivo Repeatedly Activated Persistent Luminescence Nanoparticles by Radiopharmaceuticals for Long‐Lasting Tumor Optical Imaging

Persistent luminescence nanoparticles (PLNPs) with rechargeable near‐infrared afterglow properties attract much attention for tumor diagnosis in living animals since they can avoid tissue autofluorescence and greatly improve the signal‐to‐background ratio. Using UV, visible light, or X‐ray as excitation sources to power up persistent luminescence (PL) faces the challenges such as limited tissue penetration, inefficient charging capability, or tissue damage caused by irradiation. Here, it is proved that radiopharmaceuticals can efficiently excite ZnGa₂O₄:Cr³⁺ nanoparticles (ZGCs) for both fluorescence and afterglow luminescence via Cerenkov resonance energy transfer as well as ionizing radiation. ¹⁸F‐FDG, a clinically approved tumor‐imaging radiopharmaceutical with a short decay half‐life around 110 min, is successfully used as the internal light source to in vivo excite intravenously injected ZGCs for tumor luminescence imaging over 3 h. The luminescence with similar decay time can be re‐obtained for multiple times upon injection of ¹⁸F‐FDG at any time needed with no health concern. It is believed this strategy can not only provide tumor luminescence imaging with high sensitivity, high contrast, and long decay time at desired time, but also guarantee the patients much less radiation exposure, greatly benefiting image‐guided surgery in the future.     

Photoluminescence decay kinetics of doped ZnS nanophosphors

Doped nanophosphor samples of ZnS:Mn, ZnS:Mn, Co and ZnS:Mn, Fe were prepared using a chemical precipitation method. Photoluminescence (PL) spectra were obtained and lifetime studies of the nanophosphors were carried out at room temperature. To the best of our knowledge, there are very few reports on the photoluminescence investigations of Co-doped or Fe-doped ZnS:Mn nanoparticles in the literature. Furthermore, there is no report on luminescence lifetime shortening of ZnS:Mn nanoparticles doped with Co or Fe impurity. Experimental results showed that there is considerable change in the photoluminescence spectra of ZnS:Mn nanoparticles doped with X (X = Co, Fe). The PL spectra of the ZnS:Mn, Co nanoparticle sample show three peaks at 410, 432 and 594?nm, while in the case of the ZnS:Mn, Fe nanoparticle sample the peaks are considerably different. The lifetimes are found to be in microsecond time domain for 594?nm emission, while nanosecond order lifetimes are obtained for 432 and 411?nm emission in ZnS:Mn, X nanophosphor samples. These lifetimes suggest a new additional decay channel of the carrier in the host material.     

Dual Drug Backboned Shattering Polymeric Theranostic Nanomedicine for Synergistic Eradication of Patient‐Derived Lung Cancer

Most of the current nanoparticle‐based therapeutics worldwide failing in clinical trials face three major challenges: (i) lack of an optimum drug delivery platform with precise composition, (ii) lack of a method of directly monitoring the fate of a specific drug rather than using any other labelling molecules as a compromise, and (iii) lack of reliable cancer models with high fidelity for drug screen and evaluation. Here, starting from a PP2A inhibitor demethylcantharidin (DMC) and cisplatin, the design of a dual sensitive dual drug backboned shattering polymer (DDBSP) with exact composition at a fixed DMC/Pt ratio for precise nanomedicine is shown. DDBSP self‐assembled nanoparticle (DD‐NP) can be triggered intracellularly to break down in a chain‐shattering manner to release the dual drugs payload. Moreover, DD‐NP with extremely high Pt heavy metal content in the polymer chain can directly track the drug itself via Pt‐based drug‐mediated computer tomography and ICP‐MS both in vitro and in vivo. Finally, DD‐NP is used to eradicate the tumor burden on a high‐fidelity patient‐derived lung cancer model for the first time.     

Stability and nonlinear optical properties of ZnO nanoparticles

Photoluminescence (PL) of ZnO nanoparticles of different surface states and sizes grown by several methods has been measured. The origin of luminescence and dependence of the luminescence spectrum shape and intensity on 325 nm excitation laser power are studied. Strong ultraviolet emission at 3.26 eV, weak violet emission around 3.12 eV and weak green emission at 2.40 eV have been observed in 16 nm nanoparticles capped by octylamine grown by non-hydrolytic method. The nanoparticles are stable under high power laser radiation and their PL intensity increases nonlinearly with an increasing laser power. As the nanoparticle size decreases to 12 nm, high power laser produces nonradiative centers which may quench the luminescence in a degree. Nanoparticles of 8 nm capped by PVP and uncapped nanoparticles of 14 nm are unstable and their luminescence depends on the excitation laser power. High power laser can quench O vacancy emission and enhance ultraviolet emission in PVP capped nanoparticles while vacancy emission can not be quenched in uncapped nanoparticles.     

Sizing nanomatter in biological fluids by fluorescence single particle tracking

Accurate sizing of nanoparticles in biological media is important for drug delivery and biomedical imaging applications since size directly influences the nanoparticle processing and nanotoxicity in vivo. Using fluorescence single particle tracking we have succeeded for the first time in following the aggregation of drug delivery nanoparticles in real time in undiluted whole blood. We demonstrate that, by using a suitable surface functionalization, nanoparticle aggregation in the blood circulation is prevented to a large extent.     

Porous Silicon Nanoparticle Delivery of Tandem Peptide Anti‐Infectives for the Treatment of Pseudomonas aeruginosa Lung Infections

There is an urgent need for new materials to treat bacterial infections. In order to improve antibacterial delivery, an anti‐infective nanomaterial is developed that utilizes two strategies for localization: i) a biodegradable nanoparticle carrier to localize therapeutics within the tissue, and ii) a novel tandem peptide cargo to localize payload to bacterial membranes. First, a library of antibacterial peptides is screened that combines a membrane‐localizing peptide with a toxic peptide cargo and discovers a tandem peptide that displays synergy between the two domains and is able to kill Pseudomonas aeruginosa at sub‐micromolar concentrations. To apply this material to the lung, the tandem peptide is loaded into porous silicon nanoparticles (pSiNPs). Charged peptide payloads are loaded into the pores of the pSiNP at ≈30% mass loading and ≈90% loading efficiency using phosphonate surface chemistry. When delivered to the lungs of mice, this anti‐infective nanomaterial exhibits improved safety profiles over free peptides. Moreover, treatment of a lung infection of P. aeruginosa results in a large reduction in bacterial numbers and markedly improves survival compared to untreated mice. Collectively, this study presents the selection of a bifunctional peptide‐based anti‐infective agent and its delivery via biodegradable nanoparticles for application to an animal model of lung infection.     

Recent Progress in Time‐Resolved Biosensing and Bioimaging Based on Lanthanide‐Doped Nanoparticles

Luminescent nanomaterials have attracted great attention in luminescence‐based bioanalysis due to their abundant optical and tunable surface physicochemical properties. However, luminescent nanomaterials often suffer from serious autofluorescence and light scattering interference when applied to complex biological samples. Time‐resolved luminescence methodology can efficiently eliminate autofluorescence and light scattering interference by collecting the luminescence signal of a long‐lived probe after the background signals decays completely. Lanthanides have a unique [Xe]4f^N electronic configuration and ladder‐like energy states, which endow lanthanide‐doped nanoparticles with many desirable optical properties, such as long luminescence lifetimes, large Stokes/anti‐Stokes shifts, and sharp emission bands. Due to their long luminescence lifetimes, lanthanide‐doped nanoparticles are widely used for high‐sensitive biosensing and high‐contrast bioimaging via time‐resolved luminescence methodology. In this review, recent progress in the development of lanthanide‐doped nanoparticles and their application in time‐resolved biosensing and bioimaging are summarized. At the end of this review, the current challenges and perspectives of lanthanide‐doped nanoparticles for time‐resolved bioapplications are discussed.     

Effective Labeling of Primary Somatic Stem Cells with BaTiO3 Nanocrystals for Second Harmonic Generation Imaging

While nanoparticles are an increasingly popular choice for labeling and tracking stem cells in biomedical applications such as cell therapy, their intracellular fate and subsequent effect on stem cell differentiation remain elusive. To establish an effective stem cell labeling strategy, the intracellular nanocrystal concentration should be minimized to avoid adverse effects, without compromising the intensity and persistence of the signal necessary for long‐term tracking. Here, the use of second‐harmonic generating barium titanate nanocrystals is reported, whose achievable brightness allows for high contrast stem cell labeling with at least one order of magnitude lower intracellular nanocrystals than previously reported. Their long‐term photostability enables to investigate quantitatively at the single cell level their cellular fate in hematopoietic stem cells (HSCs) using both multiphoton and electron microscopy. It is found that the concentration of nanocrystals in proliferative multipotent progenitors is over 2.5‐fold greater compared to quiescent stem cells; this difference vanishes when HSCs enter a nonquiescent, proliferative state, while their potency remains unaffected. Understanding the nanoparticle stem cell interaction allows to establish an effective and safe nanoparticle labeling strategy into somatic stem cells that can critically contribute to an understanding of their in vivo therapeutic potential.     

Luminescence Lifetime–Based In Vivo Detection with Responsive Rare Earth–Dye Nanocomposite

For years, luminescence lifetime imaging has served as a quantitative tool in indicating intracellular components and activities. However, very few studies involve the in vivo study of animals, especially in vivo stimuli‐responsive activities of animals, as both excitation and emission wavelengths should fall into the near‐infrared (NIR) optical transparent window (660–950 and 1000–1500 nm). Herein, this work reports a lifetime‐responsive nanocomposite with both excitation and emission in the NIR I window (800 nm) and lifetime in the microsecond region. The incorporation of Tm³⁺‐doped rare‐earth nanocrystals and NIR dye builds an efficient energy transfer pathway that enables a tunable luminescence lifetime range. The NaYF₄:Tm nanocrystal, which absorbs and emits photons at the same energy level, is found to be 33 times brighter than optimized core–shell upconversion nanocrystals, and proved to be an effective donor for NIR luminescence resonance energy transfer (LRET). The anti‐interference capability of luminescence lifetime signals is further confirmed by luminescence and lifetime imaging. In vivo studies also verify the lifetime response upon stimulation generated in an arthritis mouse model. This work introduces an intriguing tool for luminescence lifetime–based sensing in the microsecond region.     

pH‐Responsive PEG‐Shedding and Targeting Peptide‐Modified Nanoparticles for Dual‐Delivery of Irinotecan and microRNA to Enhance Tumor‐Specific Therapy

Irinotecan is one of the main chemotherapeutic agents for colorectal cancer (CRC). MicroRNA‐200 (miR‐200) has been reported to inhibit metastasis in cancer cells. Herein, pH‐sensitive and peptide‐modified liposomes and solid lipid nanoparticles (SLN) are designed for encapsulation of irinotecan and miR‐200, respectively. These peptides include one cell‐penetrating peptide, one ligand targeted to tumor neovasculature undergoing angiogenesis, and one mitochondria‐targeting peptide. The peptide‐modified nanoparticles are further coated with a pH‐sensitive PEG‐lipid derivative with an imine bond. These specially‐designed nanoparticles exhibit pH‐responsive release, internalization, and intracellular distribution in acidic pH of colon cancer HCT116 cells. These nanoparticles display low toxicity to blood and noncancerous intestinal cells. Delivery of miR‐200 by SLN further increases the cytotoxicity of irinotecan‐loaded liposomes against CRC cells by triggering apoptosis and suppressing RAS/β‐catenin/ZEB/multiple drug resistance (MDR) pathways. Using CRC‐bearing mice, the in vivo results further indicate that irinotecan and miR‐200 in pH‐responsive targeting nanoparticles exhibit positive therapeutic outcomes by inhibiting colorectal tumor growth and reducing systemic toxicity. Overall, successful delivery of miR and chemotherapy by multifunctional nanoparticles may modulate β‐catenin/MDR/apoptosis/metastasis signaling pathways and induce programmed cancer cell death. Thus, these pH‐responsive targeting nanoparticles may provide a potential regimen for effective treatment of colorectal cancer.     

Layered Rare‐Earth Hydroxide/Polyacrylamide Nanocomposite Hydrogels with Highly Tunable Photoluminescence

Polymer nanocomposite (NC) hydrogels, with 3D networks composed of delaminated inorganic nanoparticles and a polymer matrix, usually display super mechanical toughness. However, the few types of inorganic materials and relatively scarce research for NC hydrogel functions seriously limit their applications. For the first time layered rare‐earth hydroxide (LRH)/polyacrylamide NC hydrogels with highly tunable photoluminescence (PL) function are reported, prepared via a convenient and green in situ polymerization process. Interestingly, the NC hydrogels reveal exciting multicolored PL phenomenon (green, yellow, orange, reddish‐orange to bluish violet), long luminescence lifetime, and relatively high quantum efficiency. Furthermore, the fascinating PL function is highly tunable by adjusting LRH constituent or its concentration, and excitation wavelength. The results highlight the fabrication and applications of functional polymer NC hydrogels with highly tunable PL function.     

Time resolved spectroscopic studies on some nanophosphors

Time resolved spectroscopy is an important tool for studying photophysical processes in phosphors. Present work investigates the steady state and time resolved photoluminescence (PL) spectroscopic characteristics of ZnS, ZnO and (Zn, Mg)O nanophosphors both in powder as well as thin film form. Photoluminescence (PL) of ZnS nanophosphors typically exhibit a purple/blue emission peak termed as self activated (SA) luminescence and emission at different wavelengths arising due to dopant impurities e.g. green emission for ZnS: Cu, orange emission for ZnS: Mn and red emission for ZnS: Eu. The lifetimes obtained from decay curves range from ns to ms level and suggest the radiative recombination path involving donor-acceptor pair recombination or internal electronic transitions of the impurity atom. A series of ZnMgO nanophosphor thin films with varied Zn: Mg ratios were prepared by chemical bath deposition. Photoluminescence (PL) excitation and emission spectra exhibit variations with changing Mg ratio. Luminescence lifetime as short as 10⁻¹⁰ s was observed for ZnO and ZnMgO (100: 10) nanophosphors. With increasing Mg ratio, PL decay shifts into microsecond range. ZnO and ZnMgO alloys up to 50% Mg were prepared as powder by solid state mixing and sintering at high temperature in reducing atmosphere. Time resolved decay of PL indicated lifetime in the microsecond time scale. The novelty of the work lies in clear experimental evidence of dopants (Cu, Mn, Eu and Mg) in the decay process and luminescence life times in II–VI semiconductor nanocrystals of ZnS and ZnO. For ZnS, blue self activated luminescence decays faster than Cu and Mn related emission. For undoped ZnO nanocrystals, PL decay is in the nanosecond range whereas with Mg doping the decay becomes much slower in the microsecond range.     

Zinc Oxide Nanoparticles and Voltage‐Gated Human Kv11.1 Potassium Channels Interact through a Novel Mechanism

Membrane–nanoparticle interactions are important in determining the effects of manufactured nanomaterials on cell physiology and pathology. Here, silica, titanium, zinc, and magnesium oxide nanoparticles are screened against human hERG (K_v11.1) voltage‐gated potassium channels under a whole‐cell voltage clamp. 10 µg mL^?1 ZnO uniquely increases the amplitude of the steady‐state current, decreases the rate of hERG current inactivation during steady‐state depolarization, accelerates channel deactivation during resurgent tail currents, and shows no significant alteration of current activation rate or voltage dependence. In contrast, ZnCl₂ causes increased current suppression with increasing concentration and fails to replicate the nanoparticle effect on decreasing inactivation. The results show a novel class of nanoparticle–biomembrane interaction involving channel gating rather than channel block, and have implications for the use of nanoparticles in biomedicine, drug delivery applications, and nanotoxicology.     

Binary Nanoparticle Superlattices for Plasmonically Modulating Upconversion Luminescence

Engineering a facile and controllable approach to modulate the spectral properties of lanthanide‐doped upconversion nanoparticles (UCNPs) is always an ongoing challenge. Herein, long‐range ordered, distinct two‐dimensional (2D) binary nanoparticle superlattices (BNSLs) composed of NaREF₄:Yb/Er (RE = Y and Gd) UCNPs and plasmonic metallic nanoparticles (Au NPs), including AB, AB₃, and AB₁₃ lattices, are fabricated via a slow evaporation‐driven self‐assembly to achieve plasmonic modulation of upconversion luminescence (UCL). Optical measurements reveal that typical red–green UCL from UCNPs can be effectively modulated into reddish output in BNSLs, with a drastically shortened lifetime. Notably, for AB₃‐ and AB₁₃‐type BNSLs with more proximal Au NPs around each UCNP, modified UCL with fine‐structured spectral lineshape is observed. These differences could be interpreted by the interplay of collective plasmon resonance introduced by 2D periodic Au arrays and spectrally selective energy transfer between UCNPs and Au. Thus, fabricating UCNP‐Au BNSLs with desired lattice parameters and NP configurations could be a promising way to tailor the UCL through controlled plasmonic modulation.     

Study of dielectric and piezoelectric properties of Pb(Ni,Nb)O3–Pb(Zr,Ti)O3 ceramics using mechanically activated powder

In this paper, we report a new method to prepare the polymer/inorganic nanoparticle composites using electron irradiation-induced polymerization. The mixture of nanoparticles and MMA solution were co-irradiated by 1.6 MeV electron beam to a dose of 10, 20 and 30 kGy at a dose-rate of 60 kGy/h in air at room temperature. The products after irradiation were extracted using a soxhlet extractor with boiling xylene and investigated by X-ray diffraction (XRD), Fourier transmission infrared (FTIR), X-ray photoelectron spectroscopy (XPS), optical absorption spectra (OAP) and photoluminescence (PL). The FTIR and XPS results show that there exist some unextractable PMMA in the nanocomposites after extraction, indicating a strong interaction between the PMMA and nanoparticles. PL results show that new luminescence peaks appear at 415 and 420 nm for the nanocomposites of anatase and γ-Al₂O₃.     

Shaping Luminescent Properties of Yb3+ and Ho3+ Co‐Doped Upconverting Core–Shell β‐NaYF4 Nanoparticles by Dopant Distribution and Spacing

At the core of luminescence color and lifetime tuning of rare earth doped upconverting nanoparticles (UCNPs), is the understanding of the impact of the particle architecture for commonly used sensitizer (S) and activator (A) ions. In this respect, a series of core@shell NaYF₄ UCNPs doped with Yb³⁺ and Ho³⁺ ions are presented here, where the same dopant concentrations are distributed in different particle architectures following the scheme: YbHo core and YbHo@…, …@YbHo, Yb@Ho, Ho@Yb, YbHo@Yb, and Yb@YbHo core–shell NPs. As revealed by quantitative steady‐state and time‐resolved luminescence studies, the relative spatial distribution of the A and S ions in the UCNPs and their protection from surface quenching has a critical impact on their luminescence characteristics. Although the increased amount of Yb³⁺ ions boosts UCNP performance by amplifying the absorption, the Yb³⁺ ions can also efficiently dissipate the energy stored in the material through energy migration to the surface, thereby reducing the overall energy transfer efficiency to the activator ions. The results provide yet another proof that UC phosphor chemistry combined with materials engineering through intentional core@shell structures may help to fine‐tune the luminescence features of UCNPs for their specific future applications in biosensing, bioimaging, photovoltaics, and display technologies.