White organic light emitting diodes (WOLEDs) are promising devices for application in low energy consumption lighting since they combine the potentialities of high efficiency and inexpensive production with the appealing features of large surfaces emitting good quality white light. However, lifetime, performances and costs still have to be optimized to make WOLEDs commercially competitive as alternative lighting sources. Development of efficient and stable emitters plays a key role in the progress of WOLED technology. This tutorial review discusses the main approaches to obtain white electroluminescence with organic and organometallic emitters. Representative examples of each method are reported highlighting the most significant achievements together with open issues and challenges to be faced by future research.

In this article we highlight, by means of selected examples drawn from work performed in our or other laboratories, the features of some classes of fluorinated conjugated materials and their use in electronic devices such as electroluminescent diodes or field effect transistors. A variety of fluorinated conjugated systems, either molecular or polymeric, such as poly(phenylenevinylene)s, poly(phenyleneethynylene)s, polythiophenes, polyphenylenes, are dealt with. Attention is also focused on a different class of electroluminescent compounds, represented by the cyclometalated iridium complexes with various forms (mer and fac). In particular, fluorine atoms lower both the HOMO and LUMO energy levels. Consequently, the electron injection is made easier, the materials display a greater resistance against the degradative oxidation processes and organic n-type or ambipolar semiconducting materials may result. Moreover, the C-H...F interactions play an important role in the solid state supramolecular organization, originating a typical pi-stack arrangement which enhances the charge carrier mobility.

Homoleptic Ir(Fnppy)3 and heteroleptic (Fnppy)2Ir(acac) complexes (n = 3: F3ppy =\ud 2-(39,49,69-trifluorophenyl)pyridine; n = 4: F4ppy = 2-(39,49,59,69-tetrafluorophenyl)pyridine;\ud acac = acetylacetonate) have been synthesized and their spectroscopic properties investigated. The\ud homoleptic complexes exist as two stereoisomers, facial (fac) and meridional (mer), that have been\ud isolated and fully characterized. Their electrochemical and photophysical properties have been\ud studied both in solution and in the solid state and electroluminescent devices have been fabricated.\ud The emissive layers in devices have been obtained mixing the iridium complexes with a PVK\ud [poly(9-vinylcarbazole)] host matrix, in the presence of the electron carrier Bu-PBD [2-(4-\ud biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole]. The application of a voltage (5.0–6.5 V)\ud between the electrodes of devices leads to electro-generated blue luminescence which has similar\ud energy to the solution emissions. Interestingly, the stability of the devices made with the\ud homoleptic fluorinated iridium complexes strongly depends on the stereochemistry of these\ud phosphors and high (up to 5.5%) external quantum efficiencies for the fac complexes are\ud measured

Colloidal white emitting nanostructures were successfully fabricated by covalently binding a blue emitting oligofluorene at the surface of silica beads, that incorporate orange luminescent colloidal CdSe@ZnS quantum dots (QDs). White light was achieved by carefully tuning the size of the QDs to complementarily match the emission color of the blue fluorophore and taking into account the delicate balance between the emission of the QDs in the core of the silica beads and the amount of the organic dye bound to the silica surface. The proposed approach is highly versatile as it can be extended to the fabrication of a variety of luminescent hybrid nano-objects, playing with the complementarity of the emission color of the inorganic and organic fluorophores at the nanoscale

Diatoms are unicellular photosynthetic microalgae, ubiquitously diffused in both marine and freshwater environments, which exist worldwide with more than 100 000 species, each with different morphologies and dimensions, but typically ranging from 10 to 200 µm. A special feature of diatoms is their production of siliceous micro- to nanoporous cell walls, the frustules, whose hierarchical organization of silica layers produces extraordinarily intricate pore patterns. Due to the high surface area, mechanical resistance, unique optical features, and biocompatibility, a number of applications of diatom frustules have been investigated in photonics, sensing, optoelectronics, biomedicine, and energy conversion and storage. Current progress in diatom-based nanotechnology relies primarily on the availability of various strategies to isolate frustules, retaining their morphological features, and modify their chemical composition for applications that are not restricted to those of the bare biosilica produced by diatoms. Chemical or biological methods that decorate, integrate, convert, or mimic diatoms' biosilica shells while preserving their structural features represent powerful tools in developing scalable, low-cost routes to a wide variety of nanostructured smart materials. Here, the different approaches to chemical modification as the basis for the description of applications relating to the different materials thus obtained are presented.

Conjugated organic polymers, small molecules, and transition metal organometallic complexes are used as active semiconducting materials in electronic and optoelectronic devices including organic solar cells (OSCs), organic field effect transistors (OFETS), organic light emitting diodes (OLEDs). While some of these technologies are mature and already available on the market, research is still very active in academic and industrial laboratories to gain better performances. Major drawbacks which still limit large industrial production of some of these devices are not only the non‐optimized performances, but also stability issues and cost. In fact, wide applicability of organic electronic technology largely relies on the development of efficient, durable and cost‐effective materials. Properties of molecular and polymeric semiconductors can be properly engineered and finely tuned by the design of the conjugated molecular structure and the selective introduction of various functional groups as substituents. Selective functionalization of the conjugated backbone with fluorine atoms and fluorinated substituents has been largely demonstrated to be an effective structural modification not only for tuning optoelectronic properties, but also to affect solid state organization and to improve stability. This review covers the most important classes of materials (conjugated polymers, small molecules, and organometallic complexes) reporting for each of these classes the applications in OSCs, OFETs, and OLEDs and highlighting the role of fluorine functionalization on the properties. The literature shows intriguing results that can be achieved by fluorine functionalization, and it also points out that this research field is still promising for future progress.

Light machine: The simplest photosynthetic protein able to convert sunlight into other energy forms is covalently functionalized with a tailored organic dye to obtain a fully functional hybrid complex that outperforms the natural system in light harvesting and conversion ability.

Nanostructured biosilica produced by Thalassiosira weissflogii diatoms is covalently functionalized with the cyclic nitroxide 2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), an efficient scavenger of reactive oxygen species (ROS) in biological systems. Drug delivery properties of the TEMPO-functionalized biosilica are studied for Ciprofloxacin, an antimicrobial thoroughly employed in orthopedic or dental implant related infections. The resulting TEMPO-biosilica, combining Ciprofloxacin drug delivery with anti-oxidant properties, is demonstrated to be a suitable material for fibroblasts and osteoblast-like cells growth. Them bones gonna rise again: Covalent functionalization of nanostructured silica shells from diatoms with TEMPO radical endows biosilica with both drug-delivery properties and antioxidant activity. The resulting functional biosilica is demonstrated to be a suitable substrate for bone cell growth