Broadband near‐infrared (NIR) phosphor‐converted light emitting diode (pc‐LED) is demanded for wearable biosensing devices, but it suffers from low efficiency and low radiance. This study reports a broadband NIR Ca3‐xLuxHf2Al2+xSi1−xO12:Cr3+ garnet phosphor with emission intensity enhanced by 81.5 times. Chemical unit co‐substitution of [Lu3+−Al3+] for [Ca2+−Si4+] is responsible for the luminescence enhancement and further alters the crystal structure and electronic properties of the garnet. Using the optimized phosphor, a NIR pc‐LED with photoelectric efficiencies of 21.28%@10 mA, 15.75%@100 mA and NIR output powers of 46.09 mW@100 mA, 54.29 mW@130 mA is fabricated. The high power NIR light is observed to penetrate upper arms (≈8 cm). For application in NIR spectroscopy, the NIR pc‐LED is used as light source to measure transmission spectra of water, alcohol, and bovine hemoglobin solution. These results indicate the NIR garnet phosphor to be a promising candidate for NIR pc‐LED.

Towards efficient solid-state photoluminescence based on carbon-nanodots and starch composites Sun, M.; Qu, S.; Hao, Z.; Ji, W.; Jing, P.; Zhang, H.; Zhang, L.; Zhao, J.; Shen, D. Published in: Nanoscale DOI:10.1039/c4nr04034aLink to publication Citation for published version (APA):Sun, M., Qu, S., Hao, Z., Ji, W., Jing, P., Zhang, H., ... Shen, D. (2014). Towards efficient solid-state photoluminescence based on carbon-nanodots and starch composites. Nanoscale, 6(21), 13076-13081. DOI: 10.1039/c4nr04034a General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. A new type of environmentally friendly phosphor based on carbon nanodots (CDs) has been developed through the dispersion of CDs by integrating the CDs with starch particles. The starch particles contain large numbers of hydroxyl groups around the surfaces, which can effectively absorb the CDs, whose surfaces are functionalized by lots of carboxyl and amide groups, through hydrogen bonding. Effective dispersion of CDs on the surfaces of starch particles can suppress the non-radiative decay processes and photoluminescence (PL) quenching induced by aggregation of CDs. The starch matrix neither competes for absorbing excitation light nor absorbs the emissions of CDs, which leads to efficient PL emitting. As a result, the starch/CD phosphors with a quantum yield of ∼50% were obtained. The starch/CD phosphors show great potential in phosphor-based light emitting diodes, temperature sensors, and patterning.

The garnet Ca2LuZr2Al3O12 (CLZA) is a promising broad-band NIR phosphor for blue LED chips when it is doped with Cr3+.

A tunable full-color-emitting Ca(3)Sc(2)Si(3)O(12):Ce(3+), Mn(2+) (CSS:Ce(3+),Mn(2+)) phosphor is obtained by addition of doped ions as charge compensation. White LEDs with high R(a) (> 90) are achieved using the single CSS:Ce(3+),Mn(2+) phosphor.

The rare earth Er 31 and Yb 31 codoped system is the most attractive for showcasing energy transfer upconversion. This system can generate green and red emissions from Er 31 under infrared excitation of the sensitizer Yb 31 . It is well known that the red-emitting state can be populated from the upper green-emitting state. The contribution of multiphonon relaxation to this population is generally considered important at low excitation densities. Here, we demonstrate for the first time the importance of a previously proposed but neglected mechanism described as a cross relaxation energy transfer from Er 31 to Yb 31 , followed by an energy back transfer within the same Er 31 -Yb 31 pair. A luminescence spectroscopy study of cubic Y 2 O 3 :Er 31 , Yb 31 indicates that this mechanism can be more efficient than multiphonon relaxation, and it can even make a major contribution to the red upconversion. The study also revealed that the energy transfers involved in this mechanism take place only in the nearest Er 31 -Yb 31 pairs, and thus, it is fast and efficient at low excitation densities. Our results enable a better understanding of upconversion processes and properties in the Er 31 -Yb 31 system. Light: Science & Applications (2015) 4, e239; doi:10.1038/lsa.2015.12; published online 16 January 2015 Keywords: energy transfer; erbium-ytterbium system; upconversion luminescence INTRODUCTION Infrared to visible upconversion luminescence has been extensively studied for its fundamental value 1-3 and its various potential applications in upconversion lasers, 4 bioimaging, 5 etc. The codoping of Er 31 and a high concentration of sensitizer Yb 31 forms the most attractive energy transfer upconversion (ETU) system. Under infrared (980 nm) excitation of the sensitizer Yb 31 , this system can generate green and red upconversions originating from the 4 S 3/2 R 4 I 15/2 and 4 F 9/2 R 4 I 15/2 transitions of Er 31 , respectively. Unlike the green upconversion, the red upconversion benefits from several possible excitation mechanisms. 6,7 Multiphonon relaxation (MPR) from the upper 4 S 3/2 state and ETU from the lower intermediate 4 I 13/2 state are generally considered dominant at low infrared excitation densities because other mechanisms involving three photon processes 6,7 become important only at high infrared excitation densities, 8 which is not the topic of this work.The MPR is not the only mechanism for populating the 4 F 9/2 from the 4 S 3/2 ; a non-MPR mechanism was proposed earlier, 8 but it has not been considered important since then. This mechanism involves two sequential energy transfers between Er 31 and Yb 31 . The first step is a well-known cross-relaxation (CR) energy transfer from Er 31 in the

The α-Ca2P2O7:Eu2+, Mn2+ phosphors show two emission bands peaking at around 416 (blue) and 600nm (orange), originating from the allowed f-d transition of Eu2+ and the forbidden T14-A16 transition of Mn2+, respectively, under near ultraviolet (UV) excitation at 400nm. Spectroscopy and fluorescence lifetime measurements demonstrate that energy transfer from Eu2+ to Mn2+ performs with transfer efficiency as high as 65% for Mn2+ concentration of 12mol%. The authors have fabricated a white light emitting diode (LED) through the integration of GaN near-UV chip and two phosphor blends (α-Ca2P2O7:Eu2+, Mn2+ blue-orange phosphor and Ba2SiO4:Eu2+ green phosphor) into a single package. The white LED shows color rendering index of 78, luminescent efficiency of 9lm∕W, and low color point variation against forward-bias currents.

White light-emitting diodes (WLEDs) are candidates to revolutionize the lighting industry towards energy efficient and environmental friendly lighting and displays. The current challenges in WLEDs encompass high luminous efficiency, chromatic stability, high colourrending index and price competitiveness. Recently, the development of efficient and low-cost downconverting photoluminescent phosphors for ultraviolet/blue to white light conversion was highly investigated. Here we report a simple route to design high-efficient WLEDs by combining a commercial ultraviolet LED chip (InGaAsN, 390 nm) and boehmite (g-AlOOH) hybrid nanoplates. Unusually high quantum yields (Z yield ¼ 38-58%) result from a synergic energy transfer between the boehmite-related states and the triplet states of the benzoate ligands bound to the surface of the nanoplates. The nanoplates with Z yield ¼ 38% are able to emit white light with Commission International de l'Eclairage coordinates, colour-rendering index and correlated colour temperature values of (0.32, 0.33), 85.5 and 6,111 K, respectively; overwhelming state-of-the-art single-phase ultraviolet-pumped WLEDs phosphors.

Developing high energy density lithium secondary batteries is pivotal for satisfying the increasing demand in advanced energy storage systems. Lithium metal batteries (LMBs) have attracted growing attention due to their high theoretical capacity, but the lithium dendrites issue severely fetter their real‐world applications. It is found that reducing anion migration near lithium metal prolongs the nucleation time of dendrites, meanwhile, promoting homogeneous lithium deposition suppresses the dendritic growth. Thus, regulating ion transport in LMBs is a feasible and effective strategy for addressing the issues. Based on this, a functional separator is developed to regulate ion transport by utilizing a well‐designed metal‐organic frameworks (MOFs) coating to functionalize polypropylene (PP) separator. The well‐defined intrinsic nanochannels in MOFs and the negatively charged gap channels both restricts the free migration of anions, contributing to a high Li+ transference number of 0.68. Meanwhile, the MOFs coating with uniform porous structure promotes homogeneous lithium deposition. Consequently, a highly‐stable Li plating/stripping cycling for over 150 h is achieved. Furthermore, implementation of the separator enables LMBs with high discharge capacity, prominent rate performance and good capacity retention. This work is anticipated to aid developement of dendrite‐free LMBs by utilizing advanced separators with ion transport management.