Silica shell-assisted synthetic route for mono-disperse persistent nanophosphors with enhanced in vivo recharged near-infrared persistent luminescence

Near-infrared (NIR) persistent-luminescence nanoparticles have emerged as a new class of background-free contrast agents that are promising for in vivo imaging.The next key roadblock is to establish a robust and controllable method for synthesizing monodisperse nanoparticles with high luminescence brightness and long persistent duration.Herein,we report a synthesis strategy involving the coating/etching of the SiO2 shell to obtain a new class of small NIR highly persistent luminescent ZnGa2O4∶Cr3+,Sn4+ (ZGOCS) nanoparticles.The optimized ZGOCS nanoparticles have an excellent size distribution of ～15 nm without any agglomeration and an NIR persistent luminescence that is enhanced by a factor of 13.5,owing to the key role of the SiO2 shell in preventing nanoparticle agglomeration after annealing.The ZGOCS nanoparticles have a signal-to-noise ratio ～3 times higher than that of previously reported ZnGa2O4∶Cr3+ (ZGC-1) nanoparticles as an NIR persistent-luminescence probe for in vivo bioimaging.Moreover,the persistent-luminescence signal from the ZGOCS nanoparticles can be repeatedly re-charged in situ with external excitation by a white lightemitting diode;thus,the nanoparticles are suitable for long-term in vivo imaging applications.Our study suggests an improved strategy for fabricating novel high-performance optical nanoparticles with good biocompatibility.     

Design of dual-polarized L-probe patch antenna arrays with high isolation

An experimental study of a dual-polarized L-probe patch antenna is presented. The antenna is designed to operate at around 1.8 GHz. A "dual-feed" technique is introduced to achieve high isolation between two input ports. The proposed antenna has an impedance bandwidth of 23.8% (SWR/spl les/2), 15% (SWR/spl les/1.5) and an isolation over 30 dB. In array designs, techniques for improving the isolation between two adjacent elements of an antenna array are also investigated. A two-element array with more than 30 dB isolation is designed and tested.     

Preformed sol-gel synthesis and characterization of YAlO3

The synthesis of YAlO₃ is described from commercially-available yttria and alumina preformed sols which have nanometer particle-size ranges. The products have been characterized by X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform (DRIFT) spectra, thermogravimetry—derivative thermogravimetry—differential thermal analysis (TG-DTG-DTA), scanning electron microscopy (SEM) as well as CHN-analysis, and are similar to those prepared by the alkoxide, nitrate and citrate routes. The proposed method is a simple, cheap and rapid synthetic route.     

A strategy for simultaneously realizing the cubic-to-hexagonal phase transition and controlling the small size of NaYF4:Yb3+,Er3+ nanocrystals for in vitro cell imaging

Hexagonal-phase NaYF(4):Yb(3+),Er(3+) up-conversion nanocrystals (UCNCs) are synthesized by a combination of refluxing and hydrothermal treatment. This strategy leads to only a slight increase in particle size, from 4.5 to ca. 10 nm, during the cubic-to-hexagonal phase transition. The hexagonal UCNCs can be internalized by HeLa cells and exhibit visible emission in the cells under near-infrared excitation.     

Structure and photophysical properties of new trinuclear lanthanide complexes (Ln = Eu and Tb) with 1,10-phenanthroline

Examples of trinuclear lanthanide (Ln) complexes using bridging sulfato and hydroxo ligands for Ln = Eu and Tb are reported. Structural data demonstrate that three nine-coordinate Ln³⁺ ions are caged in a monomeric structure in [Ln₃(phen)₃(OH)(SO₄)₄(DMF)₃] · DMF · H₂O, with Ln?Ln distances slightly greater than 4 Å. The luminescence and excitation spectra have been recorded and interpreted.     

Modelling pyrolysis with dynamic heating

In literature, the reaction kinetic of pyrolysis process is often determined and modelled under constant heating rates. In reality, the heating rate of an industrial pyrolysis process is difficult or often not necessary to be kept constant. The variation of heating rate at different reaction stages, termed “dynamic heating”, governs the pyrolysis performance such as production rate, energy consumption, product quality, etc. In this work, pyrolysis progress with dynamic heating is being studied. The rate and reaction heat of tyre pyrolysis at different heating rates are obtained experimentally. A transient model considering the effect of dynamic heating was then developed and compared with the conventional static heating model. Results show that a higher heating rate favours the production of volatiles and shifts the overall pyrolysis heat flow to more endothermic. The significance of the dynamic heating model was observed for processes with large feed size and/or with high heating rate.     

Lanthanide mechanoluminescence

Mechanoluminescence(ML) is the emission of light consecutive to a mechanical force or stress imposed to a crystalline material. Many inorganic and organic compounds present this phenomenon that is known for over 400 years. Lanthanide and uranyl salts were among the first substances investigated for this property. Mechanoluminescence, also referred to as tribo luminescence, is often considered as being a badly understood phenomenon. In fact it is because of two main reasons. Firstly, a variety of different mechanical stresses, from simple rubbing, to applied pressure, crushing, impact of a weight, ultrasound,laser-generated shock wave, crystallization, dissolution of crystals, or even wind can trigger it. Secondly,ML is very sensitive to the purity and morphology of the sample: in inorganic compounds, generation of traps by doping "impurities"(e.g. lanthanide ions) is responsible for light emission so that the exact composition of the sample has to be known to a very detailed level; for chelates, the crystallization conditions are crucial since they often generate extended networks of weak interactions that are instrumental in triggering ML when they are broken. In fact mechanisms of ML are relatively well known and theories and models often reproduce very well the experiments. Additionally, practical applications are at hand,for example stress,crack,and impact sensors based on SrAl_2 O_4:Eu~Ⅱ or Et_3 NH[Eu(dbm)_4] are used to test structures and materials as diverse as road bridges, reinforced concrete elements, pressurized containers or airplane wings and to image the propagation of cracks or stress distribution. Military and security applications involve detecting the passage of vehicle or soldiers and producing counterfeiting inks while more joyful applications are luminous balls, wrapping papers and adhesive tapes. Not only bulk materials, but micro-and nanoparticles feature mechanoluminescent properties and single particle manipulation under an AFM allows one to produce light sources that could be useful to several photonic applications, including bio-applications.The review starts with a short historical background of ML, discussing definitions, and providing some theoretical bases. It then presents instrumental setups before covering all aspects of lanthanide mechanoluminescence, starting with simple salts, then doped inorganic compounds(irradiated and nonirradiated) and finally chelates. Mechanoluminescent sensors are described with various actual and potential applications. Literature is covered until April 2017. The wealth of information gathered during the past 20 years in the field and the broad understanding of the phenomenon attained show that the field is presently ready for a quantitative leap forward. Many subjects are waiting to be developed,including NIR mechanoluminescence or bio-applications based on single mechanoluminescent particle light sources; in addition, designing new types of mechanoluminescent materials with techniques paralleling the developments in other aspects of lanthanide photonics could prove extremely rewarding.     

Simultaneous synthesis and functionalization of water-soluble up-conversion nanoparticles for in-vitro cell and nude mouse imaging

Water-solubility and biocompatibility are prerequisites for rare-earth up-converting nanophosphors applied to biological imaging. In this work, we have developed a facile and one-step synthesis technique, through which water-soluble NaYF(4): Yb(3+), Er(3+) nanoparticles (NPs) with functional groups including 3-mercaptopropionic acid, 6-aminocaproic acid and poly(ethylene glycol)methyl ether on their surface can be directly prepared without any further surface treatment. Some inorganic salts will be selected as starting materials, water and some low toxic organic agents have been used as reaction media, which differs from earlier works. Structural and up-converting fluorescence are characterized by a variety of techniques. Cell uptake and in-vitro imaging of the as-synthesized NPs have been investigated using a multiphoton con-focal laser scanning microscope with a near-infrared excitation source. Internalization of the bare and functionalized NPs in human lung carcinoma A549 and human cervical carcinoma HeLa cells are studied at a nanoparticle loading of 10 μg mL(-1) over an exposure period from 30 min to 24 h. The cytotoxicity of modified NPs in HeLa cells is found to be low. In addition, the feasibility of the NPs in animal imaging has been demonstrated by subcutaneously injecting these NPs into nude mouse. The results indicated that our directly synthesized NPs coated with various functional groups are promising as bio-imaging agents due to their easy uptake, long lasting, low cytotoxicity, emissive in various human carcinoma cell lines and small animals through up-conversion with near-infrared excitation.     

Popularization of sustainable fashion: barriers and solutions

The need to reduce the harmful consequences of environmental damage is fueling the development of environmentally friendly products. However, many people believe that being fashionable and being environmentally conscious are in direct conflict, and they question whether these two concepts can coexist. The results of a questionnaire survey of 327 consumers from South Korea show that consumers’ involvement in fashion is not necessarily linked to their intention to buy and consume sustainable fashion. This finding motivated us to investigate whether there are any barriers that restrict the popularization of sustainable fashion and, if so, how we can solve such a problem. From this perspective, an in-depth interview study was conducted to consolidate the views of five fashion professionals to reveal the major barriers to popularization. The ultimate goal is to explore solutions to bridge the gap between the supply and demand for sustainable fashion. The findings of this study extend our understanding of consumers’ attitude toward two conflicting values – fashionism and environmentalism, as well as the popularization barriers of sustainable fashion. This understanding is imperative to the promotion of the green movement in the fashion industry, particularly in Asian countries.     

Synthesis and photoluminescence properties of a novel red phosphor SrLaGaO4:Mn4+

A novel Mn⁴⁺-doped strontium lanthanum gallate red phosphor SrLaGaO₄:Mn⁴⁺ has been successfully prepared via the conventional solid-state reaction method. Phase purity, photoluminescence excitation/emission spectra, concentration quenching, decay curves, and temperature-dependent photoluminescence have been investigated systematically. SrLaGaO₄:Mn⁴⁺ phosphor exhibits broad excitation band from 250 to 600 nm and emits intense red light centered at 716 nm arising from spin-forbidden transition, ²E → ⁴A₂ of Mn⁴⁺. The optimal dopant concentration of Mn⁴⁺ is determined to be 0.2 mol%. Dipole-dipole interaction is supposed to be the mechanism of concentration quenching. The crystal-field strength Dq, the Racah parameters B and C, and the nephelauxetic ratio β₁ of SrLaGaO₄:Mn⁴⁺ have been calculated according to its luminescent spectra. Our systematic investigation on this new phosphor can provide a reference for the development of red-emitting phosphor.