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1. Advancing Human-Centric LED Lighting Using Na₂MgPO₄F:Eu²⁺

   https://doi.org/10.1021/acsami.1c00909  

   Hariyani, Shruti; Brgoch, Jakoah (March 2021, ACS Applied Materials & Interfaces)

   null (Ed.)

   The proliferation of energy-efficient light-emitting diode (LED) lighting has resulted in continued exposure to blue light, which has been linked to cataract formation, circadian disruption, and mood disorders. Blue light can be readily minimized in pursuit of “human-centric” lighting using a violet LED chip (λem ≈ 405 nm) downconverted by red, green, and blue-emitting phosphors. However, few phosphors efficiently convert violet light to blue light. This work reports a new phosphor that meets this demand. Na2MgPO4F:Eu2+ can be excited by a violet LED yielding an efficient, bright blue emission. The material also shows zero thermal quenching and has outstanding chromatic stability. The chemical robustness of the phosphor was also confirmed through prolonged exposure to water and high temperatures. A prototype device using a 405 nm LED, Na2MgPO4F:Eu2+, and a green and red-emitting phosphor produces a warm white light with a higher color rendering index than a commercially purchased LED light bulb while significantly reducing the blue component. These results demonstrate the capability of Na2MgPO4F:Eu2+ as a next-generation phosphor capable of advancing human-centric lighting. 

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2. Highly Efficient Spectrally Stable Red Perovskite Light‐Emitting Diodes

   https://doi.org/10.1002/adma.201707093  

   Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu (March 2018, Advanced Materials)

   Abstract Perovskite light‐emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi‐2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light‐emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi‐2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi‐2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi‐2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m⁻²and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. 

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3. Solution Processed Bilayer Metal Halide White Light Emitting Diodes

   https://doi.org/10.1002/adma.202412239  

   Liu, He; Shonde, Tunde_Blessed; Olasupo, Oluwadara_Joshua; Manny, Tarannuma_Ferdous; Islam, Md_Sazedul; Viera, Jarek; Khizr, Mohammad; Moslemi, Sahel; Lin, Xinsong; Winfred, JS_Raaj_Vellore; et al (November 2024, Advanced Materials)

   Abstract Metal halide perovskites and perovskite‐related organic metal halide hybrids (OMHHs) have recently emerged as a new class of luminescent materials for light emitting diodes (LEDs), owing to their unique and remarkable properties, including near‐unity photoluminescence quantum efficiencies, highly tunable emission colors, and low temperature solution processing. While substantial progress has been made in developing monochromatic LEDs with electroluminescence across blue, green, red, and near‐infrared regions, achieving highly efficient and stable white electroluminescence from a single LED remains a challenging and under‐explored area. Here, a facile approach to generating white electroluminescence is reported by combining narrow sky‐blue emission from metal halide perovskites and broadband orange/red emission from zero‐dimensional (0D) OMHHs. For the proof of concept, utilizing TPPcarz⁺passivated two‐dimensional (2D) CsPbBr₃nanoplatelets (NPLs) as sky blue emitter and 0D TPPcarzSbBr₄as orange/red emitter (TPPcarz⁺= triphenyl (9‐phenyl‐9H‐carbazol‐3‐yl) phosphonium), white LEDs (WLEDs) with a solution processed bilayer structure have been fabricated to exhibit a peak external quantum efficiency (EQE) of 4.8% and luminance of 1507 cd m⁻²at the Commission Internationale de L'Eclairage (CIE) coordinate of (0.32, 0.35). This work opens a new pathway for creating highly efficient and stable WLEDs using metal halide perovskites and related materials. 

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4. Red Light–Blue Light Chromoselective C(sp ² )–X Bond Activation by Organic Helicenium-Based Photocatalysis

   https://doi.org/10.1021/jacs.3c13380  

   Hossain, Md Mubarak; Shaikh, Aslam C; Kaur, Ramandeep; Gianetti, Thomas L (March 2024, Journal of the American Chemical Society)

   Chromoselective bond activation has been achieved in organic helicenium (nPr-DMQA+)-based photoredox catalysis. Consequently, control over chromoselective C(sp2)–X bond activation in multihalogenated aromatics has been demonstrated. nPr-DMQA+ can only initiate the halogen atom transfer (XAT) pathway under red light irradiation to activate low-energy-accessible C(sp2)–I bonds. In contrast, blue light irradiation initiates consecutive photoinduced electron transfer (conPET) to activate more challenging C(sp2)–Br bonds. Comparative reaction outcomes have been demonstrated in the α-arylation of cyclic ketones with red and blue lights. Furthermore, red-light-mediated selective C(sp2)–I bonds have been activated in iodobromoarenes to keep the bromo functional handle untouched. Finally, the strength of the chromoselective catalysis has been highlighted with two-fold functionalization using both photo-to-transition metal and photo-to-photocatalyzed transformations. 

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5. Towards a Consistent Method to Form PEGDA Hydrogel Microcapsules

   Razouk, I; Bennet, C; Gimenez, C; Olabisi, R (October 2019, Biomedical Engineering Society)

   As part of the PI's outreach, a course-based undergraduate research experience engaged undergraduate women in research from examining the literature to identify a gap, formulating a research hypothesis, designing experiments to test the hypothesis, analyzing the data, writing and submitting an abstract and presenting the research to the scientific community. This project was as follows: Polyethylene glycol (PEG) has increasingly been used to reliably encapsulate cells within solid microspheres. Although hollow microcapsules have also been demonstrated, there remain challenges for their use. Microfluidics can reliably form empty hollow microcapsules, but tend to clog when cells are introduced. Emulsion methods have shown success with encapsulating cells within microcapsules; however the capsules tend to burst. Here, we compare an emulsion technique with our new dropwise method that combines extrusion with vibration of a device. Light exposure and photoinitiator concentration was varied to probe their effect on the microcapsules. 

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