Luminescent Functional Metal–Organic Frameworks

Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.

Carbon quantum dots and their applications

Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).

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Lanthanide luminescence for functional materials and bio-sciences

Lanthanide-based luminescent hybrid materials.

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

51-1: Invited Paper: Charge Injection Control of Cadmium-Free Quantum Dot Light-Emitting Diodes

The effect of heat treatments between 400°C and 500°C on electrical contacts of In, Ga, Pb, and AU to n- or p-GaAs, and Ni to n-GaAs have been studied using current-voltage (I-V), Auger electron spectroscopy and scanning electron microscopy. Ohmic contacts were formed between In and GaAs upon heating due to formation of an InGaAs surface layer with low interfacial transport barriers. The contacts between Ga or Pb and n- and p-GaAs remained rectifying due to a lack of interfacial reaction. Films of Au reacted with both n-and p-type GaAs resulting in rectangular “pits”. This led to ohmic contacts only on n-type substrates due to segregation of the Si dopants to the surface of the decomposed GaAs "pits". Dopant segregation did not occur when Au reacted with p-GaAs or Ni reacted with n-GaAs, thus these contacts remained rectifying at lower doping densities (4 x 1017 cm-3).

The Effects of Interfacial Reactions in the Formation of Ohmic Contacts to GaAs

: The objective of this research program was to synthesize luminescent oxide or halide nanoparticles with improved brightness and scintillation efficiency under excitation by energetic X-ray and gamma radiation. Improved brightness and efficiency was achieved by growth of undoped and doped nanoparticles with a core/shell nanostructure. The nanoparticle properties characterized included photoluminescence-PL, crystallography, particle size distribution, quantum efficiency and nuclear spectroscopic responses.

Strategy for Enhanced Light Output from Luminescent Nanoparticles

Auger electron spectroscopy is one of the most commonly used techniques for surface analysis. It has evolved from its first common use for solid surfaces in the late 1960s to become a tool for routine analysis of materials. This article provides a concise review of the use of Auger electron spectroscopy, with emphasis on its use for optical materials. The fundamentals of the technique are reviewed, along with a discussion of data analysis and the equipment commonly used to perform the technique. Several examples of the use of AES for optical materials are discussed.

Characterization of optical materials using Auger electron spectroscopy

The development of visible and infrared emitting ZnS wide bandgap materials for electroluminescent light emission from alternating current thin film electroluminescent (ACTFEL) devices will be reviewed. Power densities of ∼30 μW/cm 2 for the near IR emissions and visible emission at levels of -100 cd/m 2 from ZnS doped with Er, Nd or Tb have been achieved. The physics leading to light emission in these devices, the excitation mechanism(s), factors limiting optical output and prospects for obtaining emission in the mid and far infrared regions will be discussed and contrasted with the more traditional band-edge recombination devices (LEDs and Diode Lasers). In addition, both visible and IR emission has also been achieved from sputter deposited GaN doped with rare earth luminescent ions. Sputter deposition for the growth of GaN potentially provides several advantages over epitaxial techniques including large area coverage, easy scale up, lower operation costs and lower environmental hazards. The mechanism for the generation of electroluminescence in ZnS doped with lanthanide ions exploit intraband and/or interband transitions of the luminescent ions embedded in the ZnS host. Here, impact excitation or/and ionization of the rare-earth ions (luminescent centers) by ballistic electrons raises the electrons on emitting ions to an excited state. Subsequent radiative relaxation back to the ground state results in light emission. By appropriate choice of the luminescent ion, the emission wavelength can be tuned from ultraviolet to the infrared. This mechanism varies dramatically from the bandedge emission in LEDs and diode lasers. Since the transitions leading to luminescence in ACTFEL devices are localized on atoms and constitute deep quantum states, these devices normally use polycrystalline thin films with abundant defects. This is in contrast with the requirement of ultra-high purity epitaxial films for the band-edge devices. However sensitivity of ACTFEL devices to point defects will be illustrated.

Paul H. Holloway

Papers

51-1: Invited Paper: Charge Injection Control of Cadmium-Free Quantum Dot Light-Emitting Diodes

The Effects of Interfacial Reactions in the Formation of Ohmic Contacts to GaAs

Strategy for Enhanced Light Output from Luminescent Nanoparticles

Characterization of optical materials using Auger electron spectroscopy

Localized quantum state luminescence from wide bandgap ZnS and GaN thin films