1,721,014 research outputs found
Common white light sources
No full textChapter 5In this Chapter we describe the features of common light sources. We first present the spectral features of the sun and discuss its colorimetric properties. Next, we summarize the properties of traditional light sources including incandescent lamps, fluorescent lamps, and high-pressure sodium lamps. Subsequently, we discuss the white light-emitting diodes of various types
How to design quality light sources with discrete color components
No full textChapter 6White light sources using discrete emitters require careful design and optimization. The first step of the design should be determining the intended use of the light source so that application specific requirements can be addressed. Subsequently, optimal designs made of discrete emitters should be determined and finally, experimental implementation of the light source should be carried out. In this Chapter of the brief, we limit ourselves to the use of discrete emitters for indoor and outdoor lighting together with display backlighting applications. For each application, we summarize the requirements that need to be satisfied and present design guidelines to implement quality light sources made of discrete emitters
Metrics for light source design
No full textChapter 4In this part of this brief, we summarize the metrics that need to be considered for designing light sources. We start with metrics on the shade of color and then continue with color rendering and photometry
Colorimetry for LED lighting
No full textChapter 3In this Chapter, we explain the basics of colorimetry and introduce the colorimetric tools useful for designing light sources
Light stimulus and human eye
No full textChapter 2In this Chapter, we summarize the structure of the human eye and introduce the sensitivity functions of various photoreceptors and present the visual regimes and corresponding eye sensitivity functions
Light-Controlled Electrostatic Self-Assembly of Quantum Dots
No full textErdem, Talha/0000-0003-3905-376X;Electrostatic self-assembly is one of the important self-assembly mechanisms that found use in optoelectronics. Although this method enables realizing unconventional architectures, producing complicated architectures in large areas requires local control over the self-assembly process. One of the ways to achieve this control is to provide enough kinetic energy to the self-assembling nanoparticles so that they can escape electrostatic attraction. We hypothesize that this energy can be delivered to the nanoparticles by treating them with light that can be absorbed by the particles. Here, we test this idea to tailor the electrostatic self-assembly of semiconductor quantum dots (QDs) using a laser. Employing fluorescence and atomic force microscopy, we demonstrate that the QDs are not attached to the substrate in regions where they are exposed to light while they are coated in the absence of optical excitation. We further conduct theoretical analysis to show that elevated temperatures indeed allow the QDs to escape the electrostatic attraction of the charged polymers on the surface. We also demonstrate that increasing the temperature during the coating process without irradiating the sample gives similar results as the case when the sample was irradiated. Finally, we fabricate an uncoated region on the self-assembled QD film with dimensions of similar to 200 mu m x 0.5 cm to demonstrate the feasibility of our approach to control the bottom-up self-assembly. We believe that our results may pave the way for a cost-effective and sustainable approach for the fabrication of nanoelectronic and optoelectronic devices.T?rkiye Bilimsel ve Teknolojik Arastirma Kurumu [120C124, TUBA-GEBIP]; Science Academy (Bilim Akademisi) [YOK, YOK 100/2000]We acknowledge funding from Tubitak (Grant No. 120C124). TE is also grateful to TUBA for the TUBA-GEBIP Award and Science Academy (Bilim Akademisi) for the BAGEP Award. ZS acknowledges the Higher Education Council (YOK) for support obtained from the YOK 100/2000 Program
IŞIK EMİCİ OPTOELEKTRONİK CİHAZLARIN ÜRETİMİ VE YENİ UYGULAMALARI
Full text linkFabrication of optoelectronic devices relies on expensive, energy-consuming conventional tools including chemical vapor deposition, lithography, and metal evaporation. Developing an alternative technology would contribute to the efforts on achieving a sustainable optoelectronics technology. Keeping this in our focus, here we present a simple technique to fabricate visible photodetectors. These fully solution-processed and transparent metal-semiconductor-metal photodetectors employ silver nanowires (Ag NW) as the transparent electrodes replacing the indium-tin-oxide (ITO) commonly used in optoelectronic devices. By repeatedly spin coating Ag NW on a glass substrate followed by the coating of ZnO nanoparticles, we obtained a highly conductive transparent electrode reaching a sheet resistance of 95 Ω/□. The transmittance of the Ag NW-ZnO films was 84% at 450 nm while the transmittance of the ITO films was 90% at the same wavelength. Following the formation of the conductive film, we scratched it using a heated surgical blade to open a gap which is ~30 µm forming an insulating line. As the active layer, we drop-casted red-emitting CdSe/ZnS core-shell colloidal quantum dots (CQDs) onto this gap. These visible CQD-based photodetectors exhibited responsivities and detectivities up to 8.5 mA/W and 0.95x109 Jones, respectively. These proof-of-concept photodetectors show that the environmentally friendly, low-cost, and energy-saving technique presented here can be an alternative to conventional, high-cost, and energy-hungry techniques while fabricating light-harvesting devices.Optoelektronik cihazların üretimi, kimyasal buhar kaplama, litografi ve metal buharlaştırma dahil olmak üzere pahalı, enerji tüketen geleneksel araçlara dayanır. Alternatif bir teknolojinin geliştirilmesi, sürdürülebilir bir optoelektronik teknolojisine ulaşma çabalarına katkıda bulunacaktır. Bunu odak noktamızda tutarak, burada görünür fotodedektörleri imal etmek için basit bir teknik sunuyoruz. Bu tamamen çözelti ile işlenmiş ve şeffaf metal-yarı iletken-metal fotodedektörler, optoelektronik cihazlarda yaygın olarak kullanılan indiyum-kalay oksitin (ITO) yerini alan şeffaf elektrotlar olarak gümüş nanotelleri (Ag NW) kullanmıştır. Bir cam substrat üzerinde Ag NW'leri tekrar tekrar döndürerek kaplamayı takiben ZnO nanoparçacıklarının kaplanmasıyla, 95 Ω/□'lik bir tabaka direncine ulaşan oldukça iletken şeffaf bir elektrot elde edilmiştir. Ag NW-ZnO filmlerinin geçirgenliği 450 nm'de %84 iken, aynı dalga boyunda ITO filmlerinin geçirgenliği %90 olmuştur. İletken filmin oluşumunu takiben, bir yalıtım hattı oluşturan ~30 µm'lik bir boşluk açmak için ısıtılmış bir cerrahi bıçak kullanarak film çizilmiştir. Aktif katman olarak, bu boşluğa kırmızı yayan CdSe/ZnS çekirdek-kabuk kolloidal kuantum noktalarını (KKN'ler) damlatılmıştır. Bu görünür KKN tabanlı fotodedektörler, sırasıyla 8.5 mA/W ve 0.95x109 Jones'a kadar duyarlılık ve algılama sergilemiştir. Bu kavram kanıtı fotodedektörler, burada sunulan çevre dostu, düşük maliyetli ve enerji tasarruflu tekniğin, ışık hasat eden cihazları üretirken geleneksel, yüksek maliyetli ve çok enerji tüketen tekniklere bir alternatif olabileceğini göstermektedir.TABLE OF CONTENTS
1. INTRODUCTION .................................................................................................... 1
2. PHOTODETECTORS ...............................................................................................................4
2.1 THE P-N JUNCTION PHOTODIODES............................................................................. 5
2.2 THE PIN PHOTODIODES ............................................................................................. 7
2.3 AVALANCHE PHOTODIDES........................................................................................ 8
2.4 SCHOTTKHY JUNCTION PHOTODIODES.................................................................... 10
2.5 COLLOIDAL QUANTUM DOT PHOTODIODES............................................................. 12
3. SILVER NANOWIRES (AG NW) ......................................................................................15
3.1 SILVER NANOWIRES AS TRANSPARENT ELECTRODES .............................................. 15
3.2 SYNTHESIS TECHNIQUES ........................................................................................ 16
3.2.1 Synthesis of Ag NW........................................................................................ 17
3.3 ELECTRICAL PROPERTIES OF AG NW THIN FILMS..................................................... 18
3.4 OPTICAL PROPERTIES OF AG NW THIN FILMS .......................................................... 20
4. ZINC OXIDE NANOPARTICLES (ZNO NP)...............................................................22
4.1 ZINC OXIDE NANOPARTICLES AS ADDITIVES FOR TRANSPARENT AND CONDUCTIVE
AG NW FILM ................................................................................................................. 22
4.2 SYNTHESIS TECHNIQUES ........................................................................................ 22
4.2.1 Synthesis of ZnO NP and integration with Ag NW films............................... 23
4.3 OPTICAL PROPERTIES OF ZNO NP.......................................................................... 24
4.4 ELECTRICAL PROPERTIES OF ZNO NP.................................................................... 26
5. COLLOIDAL QUANTUM DOTS (CQDS).....................................................................28
5.1 COLLOIDAL QUANTUM DOTS FOR PHOTODETECTORS ............................................. 22
5.2 SYNTHESIS TECHNIQUES ........................................................................................ 32
5.2.1 Synthesis of CdSe/ZnS core/shell CQDs........................................................ 33
5.3 OPTICAL PROPERTIES OF THE CQDS ...................................................................... 34
6. FABRICATION OF SOLUTION PROCESSED CQD PHOTODETECTORS
............................................................................................................................................................35
6.1 SAMPLE FABRICATION ........................................................................................... 35
6.2 CHARACTERIZATION .............................................................................................. 38
6.3 RESULTS AND DISCUSSION..................................................................................... 39
7. CONCLUSIONS AND FUTURE PROSPECTS............................................................42
7.1 CONCLUSIONS ........................................................................................................ 42
7.2 SOCIETAL IMPACT AND CONTRIBUTION TO GLOBAL SUSTAINABILITY................... 43
7.3 FUTURE PROSPECTS ............................................................................................... 4
Effects of Silver Nanowires and Their Surface Modification on Electromagnetic Interference, Transport and Mechanical Properties of an Aerospace Grade Epoxy
No full textMutlugun, Evren/0000-0003-3715-5594; Oz, Yahya/0000-0003-3784-0495; Erdem, Talha/0000-0003-3905-376X;The aerospace industry has progressively grown its use of composites. Electrically conductive nanocomposites are among important modern materials for this sector. We report on a bulk composite containing silver nanowires (AgNW) and an aerospace grade epoxy for use in carbon fiber reinforced polymers (CFRPs). AgNWs' surfaces were also modified to enhance their ability to be dispersed in epoxy. Composites were obtained by use of three-roll milling which is of major interest for industrial applications, especially for the aerospace sector, since the process is scalable and works for aerospace grade resins with high curing temperatures. Our main objective is to improve the electromagnetic interference (EMI) shielding performance of CFRPs via improving the properties of the resin material. The addition of AgNWs did not considerably alter the flexural strength of the epoxy, however the composite with surface-modified AgNWs has a 46 % higher flexural strength. Adding AgNWs over a low threshold concentration of 0.05 wt% significantly enhanced the electrical conductivity. Conductivities above the percolation threshold lie around 102 S/m. At a concentration of 5 wt% AgNW, the EMI shielding efficiency (SE) of epoxy increased from 3.49 to 12.31 dB. Moreover, the thermal stability of the epoxy was unaffected by AgNWs. As a result, it was discovered that (surface modified) AgNWs improved the (multifunctional) capabilities of the aerospace grade epoxy resin which might be used in CFRPs to further enhance properties of composites parts, demonstrating suitability of AgNWs' as a reinforcement material in aerospace applications.Scientific and Technological Research Council of Turkey within the 1004 program [20AG001, 20AG020, 20AG026]The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article:Authors gratefully acknowledge financial support by the Scientific and Technological Research Council of Turkey within the 1004 program (project ns. 20AG001, 20AG020 and 20AG026)
Koloidal nanomalzemelerin akıllı kendinden dizilimi ile nanofotonik mimarilerin tasarımı ve uygulaması
Full text linkDNA-driven self-assembly techniques offer precise control over the positioning of colloidal nanoparticles through specific Watson–Crick interactions, and its reversibility via controlling the temperature of medium. This thesis explores an alternative strategy to control DNA-functionalized nanoparticles' binding/unbinding process by leveraging laser radiation, inducing localized heating within the nanoparticles to facilitate disassociation. First, we demonstrate the active manipulation of the optical properties of DNA-assembled gold nanoparticle networks via external optical excitation. Specifically, irradiation with a green hand-held laser yields a substantial ∼30% increase in total transmittance, accompanied by a transition from opaque to transparent states observable in optical microscopy images. The reversibility of this process is demonstrated by the restoration of the nanoparticle network post-irradiation cessation, underscoring the efficacy of optical excitation in tailoring both the structure and optical characteristics of DNA-mediated nanoparticle assemblies. Second, we introduce a method to tailor DNA-driven self-assembly of semiconductor nanoparticles on glass by applying an external optical field. A green laser directs the assembly of DNA-functionalized red-emitting quantum dots (QDs) on DNA-functionalized glass, leaving uncoated spots owing to localized heating. This effect becomes prominent after three hours of radiation using a laser with an irradiance of 57.1 W/cm2. Experiments with different lasers and nanoparticle types confirm the role of laser-induced heating in preventing QD-glass bonding via DNA-DNA interaction. Secondary coating of previously uncoated spots with DNA-functionalized green-emitting QDs and dye-functionalized DNAs indicates a successful hierarchical self-assembly. Our findings highlight the potential of light-assisted DNA-driven self-assembly for diverse nanoparticle architectures, promising applications in optoelectronics and nanophotonics. Keywords: Programmable self-assembly, DNA-driven self-assembly, localized heating, colloidal nanoparticles, DNA conjugation.DNA tabanlı kendiliğinden dizilim teknikleri, özgül Watson-Crick etkileşimleri aracılığıyla kolloidal nanoparçacıkların yerleşimini hassas bir şekilde kontrol etmeyi ve ortamın sıcaklığını kontrol ederek bu sürecin geri dönüştürülebilirliğini sağlamayı mümkün kılar. Bu tez, lazer ışınımı kullanarak DNA ile işlevselleştirilmiş nanoparçacıkların bağlanma/ayrılma sürecini kontrol etmek için alternatif bir strateji araştırmaktadır. Bu tezde, ilk olarak, DNA ile birleştirilmiş altın nanopartikül ağlarının optik özelliklerinin, dış optik uyarım yoluyla aktif olarak nasıl manipüle edilebileceği gösterilmiştir. Özellikle, yeşil bir el lazeri ile ışınlandığında, toplam geçirgenlikte yaklaşık %30'luk önemli bir artış gözlemlenmiş, buna optik mikroskop görüntülerinde gözlemlenebilen opak durumdan şeffaf duruma geçiş eşlik etmiştir. Bu sürecin tersine çevrilebilirliği, ışınlamanın kesilmesinden sonra nanoparçacık ağının restorasyonu ile kanıtlanmıştır. Bu gözlem, DNA-takılı nanoparçacık ağlarının hem yapısını hem de optik özelliklerini uyarlamada optik uyarmanın etkinliğinin altını çizer. İkinci olarak, harici bir optik alan uygulayarak, DNA-takılı yarı iletken nanoparçacıkların eşlenik DNA-takılı cam yüzeyler üzerinde birleşmesini kontrol etmek için bir yöntem sunulmuştur. Çalışmalarımızda, yeşil bir lazer, DNA-takılı cam üzerinde kırmızı ışık yayan DNA-takılı kuantum noktalarının birleşmesini yönlendirmiş ve lokal ısıtma nedeniyle kaplanmamış noktalar bırakmıştır. Bu etki, 57.1 W/cm² ışınım yoğunluğuna sahip bir lazer kullanılarak üç saatlik ışınım sonrasında belirgin hale gelmiştir. Farklı lazerler ve nanoparçacık türleri ile yapılan deneyler, lazer kaynaklı ısıtmanın DNA-DNA etkileşimi ile kuantum nokta-cam bağlanmasını önlemedeki rolünü doğrulamıştır. Önceden kaplanmamış noktaların DNA takılı yeşil ışık yayan kuantum noktalar ve boya takılı DNA'lar ile ikincil kaplanması, hiyerarşik birleşmeyi göstermiştir. Bulgularımız, çeşitli nanoparçacık mimarileri için ışık destekli DNA tabanlı kendiliğinden birleşmenin potansiyelini vurgulamakta, optoelektronik ve nanofotonik alanlarında yenilikçi uygulamalar vaat etmektedir. Anahtar kelimeler: Programlanabilir kendinden dizilim, DNA-tabanlı kendinden dizilim, yerel ısıtma, koloidal nanoparçacıklar, DNA bağlama
Osmotic-Pressure Nematic Ordering in Suspensions of Laponite and Carboxy Methyl Cellulose
No full textMutlugun, Evren/0000-0003-3715-5594; Yazici, Ahmet Faruk/0000-0003-2747-7856; Eiser, Erika/0000-0003-2881-8157; Erdem, Talha/0000-0003-3905-376XLaponite is a synthetic clay that is known to form gels in aqueous suspensions at low concentrations (0.01 g/cm(3)) Although it is expected to form lyotropic liquid crystals, such phases usually do not form, as a consequence of laponite's tendency to form gels at concentrations below the threshold for liquid crystal formation. Here we show that macroscopic, birefringent phases of laponite can be prepared through osmotic compression of a laponite solution by an aqueous solution of carboxy methyl cellulose (CMC). We present polarization imaging studies showing how the initially dilute, isotropic laponite phase shrinks while developing typical birefringence colors between crossed polarizers. Using the MichelLevy interference charts, we were able to extract the refractive index and orientation of the laponite nanodisks in the compressed region. Our observations allow us to propose a tentative state diagram, indicating the concentration regions for which we obtain optically anisotropic gels.Winton Program for the Physics of Sustainability; Royal SocietyWe thank the Winton Program for the Physics of Sustainability for financial support. T.E. and A.F.Y. thank the Royal Society for the Newton International Fellowship Alumni Follow-on Funding. E.E. thanks Daan Frenkel for insightful discussions and expresses her gratitude to Emily Carter, whose example shows that it is possible to be an outstanding scientist and at the same time an exceptional human being
- …
