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Materials, Volume 3, Issue 5 (May 2010), Pages 2947-3467

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Research

Jump to: Review

Open AccessArticle Long Term Fatigue Behavior of Zirconia Based Dental Ceramics
Materials 2010, 3(5), 2975-2985; doi:10.3390/ma3052975
Received: 3 February 2010 / Revised: 3 April 2010 / Accepted: 12 April 2010 / Published: 28 April 2010
Cited by 9 | PDF Full-text (273 KB) | HTML Full-text | XML Full-text
Abstract
This study evaluated the influence of cyclic loading on zirconia bar-shaped specimens after being subjected to three different surface treatments: particle abrasion with either 50 μm or 110 μm alumina and grinding with diamond points, while polished specimens served as a control. Statistical
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This study evaluated the influence of cyclic loading on zirconia bar-shaped specimens after being subjected to three different surface treatments: particle abrasion with either 50 μm or 110 μm alumina and grinding with diamond points, while polished specimens served as a control. Statistical analysis revealed significant reduction (38-67%) in flexure strength (P < 0.001) after three million cycles of dynamic loading for all surface treatments. Scanning electron imaging revealed grain boundary thickening, grain pull-out, and micro-cracking as the main structural defects. The results suggest that various surface treatments of zirconia based dental ceramics may significantly influence their long term fatigue resistance in the oral environment. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
Open AccessArticle A Green Method for Processing Polymers using Dense Gas Technology
Materials 2010, 3(5), 3188-3203; doi:10.3390/ma3053188
Received: 29 March 2010 / Revised: 27 April 2010 / Accepted: 6 May 2010 / Published: 11 May 2010
Cited by 3 | PDF Full-text (3702 KB) | HTML Full-text | XML Full-text
Abstract
Dense CO2 can be used as an environmentally-benign polymer processing medium because of its liquid-like densities and gas-like mass transfer properties.In this work, polymer bio-blends of polycarbonate (PC), a biocompatible polymer, and polycaprolactone (PCL), a biodegradable polymer were prepared. Dense CO2
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Dense CO2 can be used as an environmentally-benign polymer processing medium because of its liquid-like densities and gas-like mass transfer properties.In this work, polymer bio-blends of polycarbonate (PC), a biocompatible polymer, and polycaprolactone (PCL), a biodegradable polymer were prepared. Dense CO2 was used as a reaction medium for the melt-phase PC polymerization in the presence of dense CO2-swollen PCL particles and this method was used to prepare porous PC/PCL blends. To extend the applicability of dense CO2 to the biomedical industry and polymer blend processing, the impregnation of ibuprofen into the blend was conducted and subsequent dissolution characteristics were observed. Full article
(This article belongs to the Special Issue Supercritical Fluids)
Open AccessArticle Thin film of Poly(acrylic acid-co-allyl acrylate) as a Sacrificial Protective Layer for Hydrophilic Self Cleaning Glass
Materials 2010, 3(5), 3369-3384; doi:10.3390/ma3053369
Received: 3 May 2010 / Accepted: 19 May 2010 / Published: 25 May 2010
Cited by 2 | PDF Full-text (281 KB) | HTML Full-text | XML Full-text
Abstract
Poly(acrylic acid-co-allyl acrylate) statistical copolymers were synthesized in a controlled manner in two steps: first tert.butyl acrylate and allyl acrylate were polymerized via atom transfer radical polymerization (ATRP) and afterwords the tert.butyl protective groups were removed via hydrolysis. Samples
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Poly(acrylic acid-co-allyl acrylate) statistical copolymers were synthesized in a controlled manner in two steps: first tert.butyl acrylate and allyl acrylate were polymerized via atom transfer radical polymerization (ATRP) and afterwords the tert.butyl protective groups were removed via hydrolysis. Samples of self cleaning glass (SCG) were coated with thin films of poly(acrylic acid-co-allyl acrylate) and cross-linked afterwards by UV irradiation (in the presence of a photoinitiator and an accelerator). Solution cast thin films were transparent and homogeneous before and after UV cross-linking. The irradiated samples were found to be hydrophilic (Θ < 20°) and water insoluble. The coating prevented the spontaneous hydrophobization of the SCG by residual silicon exhaled from the sealing material. The TiO2 photocatalyst that covers the glass surface was found to strip the protective coating. The rate of the photooxidation process was measured by IR spectroscopy. The real field performance of the protective coating was also tested. Full article
(This article belongs to the Special Issue Advances in Surface Coatings)
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Review

Jump to: Research

Open AccessReview Advances in Porous Biomaterials for Dental and Orthopaedic Applications
Materials 2010, 3(5), 2947-2974; doi:10.3390/ma3052947
Received: 5 February 2010 / Revised: 18 April 2010 / Accepted: 22 April 2010 / Published: 28 April 2010
Cited by 35 | PDF Full-text (334 KB) | HTML Full-text | XML Full-text
Abstract
The connective hard tissues bone and teeth are highly porous on a micrometer scale, but show high values of compression strength at a relatively low weight. The fabrication of porous materials has been actively researched and different processes have been developed that vary
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The connective hard tissues bone and teeth are highly porous on a micrometer scale, but show high values of compression strength at a relatively low weight. The fabrication of porous materials has been actively researched and different processes have been developed that vary in preparation complexity and also in the type of porous material that they produce. Methodologies are available for determination of pore properties. The purpose of the paper is to give an overview of these methods, the role of porosity in natural porous materials and the effect of pore properties on the living tissues. The minimum pore size required to allow the ingrowth of mineralized tissue seems to be in the order of 50 µm: larger pore sizes seem to improve speed and depth of penetration of mineralized tissues into the biomaterial, but on the other hand impair the mechanical properties. The optimal pore size is therefore dependent on the application and the used material. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
Open AccessReview Development of Biomedical Polymer-Silicate Nanocomposites: A Materials Science Perspective
Materials 2010, 3(5), 2986-3005; doi:10.3390/ma3052986
Received: 11 March 2010 / Revised: 10 April 2010 / Accepted: 16 April 2010 / Published: 28 April 2010
Cited by 44 | PDF Full-text (510 KB) | HTML Full-text | XML Full-text
Abstract
Biomedical polymer-silicate nanocomposites have potential to become critically important to the development of biomedical applications, ranging from diagnostic and therapeutic devices, tissue regeneration and drug delivery matrixes to various bio-technologies that are inspired by biology but have only indirect biomedical relation. The fundamental
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Biomedical polymer-silicate nanocomposites have potential to become critically important to the development of biomedical applications, ranging from diagnostic and therapeutic devices, tissue regeneration and drug delivery matrixes to various bio-technologies that are inspired by biology but have only indirect biomedical relation. The fundamental understanding of polymer-nanoparticle interactions is absolutely necessary to control structure-property relationships of materials that need to work within the chemical, physical and biological constraints required by an application. This review summarizes the most recent published strategies to design and develop polymer-silicate nanocomposites (including clay based silicate nanoparticles and bioactive glass nanoparticles) for a variety of biomedical applications. Emerging trends in bio-technological and biomedical nanocomposites are highlighted and potential new fields of applications are examined. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
Open AccessReview Macroporous Semiconductors
Materials 2010, 3(5), 3006-3076; doi:10.3390/ma3053006
Received: 19 February 2010 / Revised: 30 March 2010 / Accepted: 30 April 2010 / Published: 7 May 2010
Cited by 37 | PDF Full-text (5734 KB) | HTML Full-text | XML Full-text
Abstract
Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 µm; morphologies from perfect pore crystal to fractal) and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds
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Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 µm; morphologies from perfect pore crystal to fractal) and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds of pores obtained in semiconductors like Ge, Si, III-V, and II-VI compound semiconductors are systematically reviewed, emphasizing macropores. Essentials of pore formation mechanisms will be discussed, focusing on differences and some open questions but in particular on common properties. Possible applications of porous semiconductors, including for example high explosives, high efficiency electrodes for Li ion batteries, drug delivery systems, solar cells, thermoelectric elements and many novel electronic, optical or sensor devices, will be introduced and discussed. Full article
(This article belongs to the Special Issue Porous Materials)
Open AccessReview Fluorinated Poly(p-phenylenevinylene)s: Synthesis and Optical Properties of an Intriguing Class of Luminescent Polymers
Materials 2010, 3(5), 3077-3091; doi:10.3390/ma3053077
Received: 18 February 2010 / Revised: 22 April 2010 / Accepted: 27 April 2010 / Published: 7 May 2010
Cited by 14 | PDF Full-text (459 KB) | HTML Full-text | XML Full-text
Abstract
This review is an overview of our previous work on the synthesis and properties of poly(p-phenylenevinylene)s (PPVs) selectively fluorinated in different positions of the conjugated backbone. Both the synthetic challenges and the effects of functionalization with fluorine atoms on the optical
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This review is an overview of our previous work on the synthesis and properties of poly(p-phenylenevinylene)s (PPVs) selectively fluorinated in different positions of the conjugated backbone. Both the synthetic challenges and the effects of functionalization with fluorine atoms on the optical behavior are discussed, highlighting the peculiarities and the interest of this class of conjugated polymers. A general polymerization protocol for PPVs, that is based on the Pd-catalyzed Stille cross-coupling reaction of bis-stannylated vinylene monomers with aromatic bis-halides, has been successfully extended to the synthesis of selectively fluorinated poly(p-phenylenevinylene)s. The properties of a series of these PPVs differing in the number and positions of the fluorine atoms on the conjugated backbone have been studied, even in comparison with the non-fluorinated counterparts. The intriguing optical features of the resulting materials are discussed considering not only the role of the electronic and steric effects induced by the fluorine substituents, but also the impact of the fluorination on the solid state organization and intermolecular interactions. Full article
(This article belongs to the Special Issue Organic Electronic Materials)
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Open AccessReview Synthesis Methods of Carbon Nanotubes and Related Materials
Materials 2010, 3(5), 3092-3140; doi:10.3390/ma3053092
Received: 26 February 2010 / Revised: 31 March 2010 / Accepted: 30 April 2010 / Published: 7 May 2010
Cited by 44 | PDF Full-text (2465 KB) | HTML Full-text | XML Full-text
Abstract
The challenge on carbon nanotubes is still the subject of many research groups. While in the first years the focus was on the new synthesis methods, new carbon sources and support materials, recently, the application possibilities are the principal arguments of the studies.
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The challenge on carbon nanotubes is still the subject of many research groups. While in the first years the focus was on the new synthesis methods, new carbon sources and support materials, recently, the application possibilities are the principal arguments of the studies. The three main synthesis methods discussed in this review are the arc discharge, the laser ablation and the chemical vapour deposition (CVD) with a special regard to the latter one. In the early stage of the nanotube production the first two methods were utilized mainly for the production of SWNTs while the third one produced mainly MWNTs. The principle of CVD is the decomposition of various hydrocarbons over transition metal supported catalyst. Single-walled (SWNT), multi-walled (MWNT) and coiled carbon nanotubes are produced. In some case, interesting carbonaceous materials are formed during the synthesis process, such as bamboo-like tubes, onions, horn-like structures. In this paper, we refer to the progresses made in the field of the synthesis techniques of carbon nanotubes in the last decade. Full article
(This article belongs to the Special Issue Synthesis of Carbon Nanotube)
Open AccessReview Progress of Multi Functional Properties of Organic-Inorganic Hybrid System, A[FeIIFeIIIX3] (A = (n-CnH2n+1)4N, Spiropyran; X = C2O2S2, C2OS3, C2O3S)
Materials 2010, 3(5), 3141-3187; doi:10.3390/ma3053141
Received: 22 February 2010 / Revised: 16 April 2010 / Accepted: 30 April 2010 / Published: 11 May 2010
Cited by 4 | PDF Full-text (1732 KB) | HTML Full-text | XML Full-text
Abstract
In the case of mixed-valence systems whose spin states are situated in the spin crossover region, new types of conjugated phenomena coupled with spin and charge are expected. From this viewpoint, we have investigated the multifunctional properties coupled with spin, charge and photon
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In the case of mixed-valence systems whose spin states are situated in the spin crossover region, new types of conjugated phenomena coupled with spin and charge are expected. From this viewpoint, we have investigated the multifunctional properties coupled with spin, charge and photon for the organic-inorganic hybrid system, A[FeIIFeIIIX3](A = (n-CnH2n+1)4N, spiropyran; X = dto(C2O2S2), tto(C2OS3), mto(C2O3S)). A[FeIIFeIII(dto)3] and A[FeIIFeIII(tto)3] undergo the ferromagnetic phase transitions, while A[FeIIFeIII(mto)3] undergoes a ferrimagnetic transition. In (n-CnH2n+1)4N [FeIIFeIII(dto)3](n = 3,4), a new type of phase transition called charge transfer phase transition (CTPT) takes place around 120 K, where the thermally induced charge transfer between FeII and FeIII occurs reversibly. At the CTPT, the iron valence state dynamically fluctuated with a frequency of about 0.1 MHz, which was confirmed by means of muon spin relaxation. The charge transfer phase transition and the ferromagnetic transition for (n-CnH2n+1)4N[FeIIFeIII(dto)3] remarkably depend on the size of intercalated cation. In the case of (SP)[FeIIFeIII(dto)3](SP = spiropyran), the photoinduced isomerization of SP under UV irradiation induces the charge transfer phase transition in the [FeIIFeIII(dto)3] layer and the remarkable change of the ferromagnetic transition temperature. In the case of (n-CnH2n+1)4N[FeIIFeIII(mto)3](mto = C2O3S), a rapid spin equilibrium between the high-spin state (S = 5/2) and the low-spin state (S = 1/2) at the FeIIIO3S3 site takes place in a wide temperature range, which induces the valence fluctuation of the FeS3O3 and FeO6 sites through the ferromagnetic coupling between the low spin state (S = 1/2) of the FeIIIS3O3 site and the high spin state (S = 2) of the FeIIO6 site. Full article
(This article belongs to the Special Issue Inorganic-Organic Hybrid Materials)
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Open AccessReview A Brief Review of Chelators for Radiolabeling Oligomers
Materials 2010, 3(5), 3204-3217; doi:10.3390/ma3053204
Received: 13 March 2010 / Revised: 26 March 2010 / Accepted: 10 May 2010 / Published: 14 May 2010
Cited by 3 | PDF Full-text (368 KB) | HTML Full-text | XML Full-text
Abstract
The chemical modification of oligomers such as DNA, PNA, MORF, LNA to attach radionuclides for nuclear imaging and radiotherapy applications has become a field rich in innovation as older methods are improved and new methods are introduced. This review intends to provide a
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The chemical modification of oligomers such as DNA, PNA, MORF, LNA to attach radionuclides for nuclear imaging and radiotherapy applications has become a field rich in innovation as older methods are improved and new methods are introduced. This review intends to provide a brief overview of several chelators currently in use for the labeling of oligomers with metallic radionuclides such as 99mTc, 111In and 188Re. While DNA and its analogs have been radiolabeled with important radionuclides of nonmetals such as 32P, 35S, 14C, 18F and 125I, the labeling methods for these isotopes involve covalent chemistry that is quite distinct from the coordinate-covalent chelation chemistry described herein. In this review, we provide a summary of the several chelators that have been covalently conjugated to oligomers for the purpose of radiolabeling with metallic radionuclides by chelation and including details on the conjugation, the choice of radionuclides and labeling methods. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
Open AccessReview Star-Shaped Conjugated Systems
Materials 2010, 3(5), 3218-3330; doi:10.3390/ma3053218
Received: 29 January 2010 / Revised: 1 April 2010 / Accepted: 28 April 2010 / Published: 19 May 2010
Cited by 52 | PDF Full-text (1218 KB) | HTML Full-text | XML Full-text
Abstract
The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems,
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The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
Open AccessReview Use of Temporary Implantable Biomaterials to Reduce Leg Pain and Back Pain in Patients with Sciatica and Lumbar Disc Herniation
Materials 2010, 3(5), 3331-3368; doi:10.3390/ma3053331
Received: 23 January 2010 / Revised: 13 May 2010 / Accepted: 17 May 2010 / Published: 19 May 2010
Cited by 2 | PDF Full-text (394 KB) | HTML Full-text | XML Full-text
Abstract
The principle etiology of leg pain (sciatica) from lumbar disc herniation is mechanical compression of the nerve root. Sciatica is reduced by decompression of the herniated disc, i.e., removing mechanical compression of the nerve root. Decompression surgery typically reduces sciatica more than
[...] Read more.
The principle etiology of leg pain (sciatica) from lumbar disc herniation is mechanical compression of the nerve root. Sciatica is reduced by decompression of the herniated disc, i.e., removing mechanical compression of the nerve root. Decompression surgery typically reduces sciatica more than lumbar back pain (LBP). Decompression surgery reduces mechanical compression of the nerve root. However, decompression surgery does not directly reduce sensitization of the sensory nerves in the epidural space and disc. In addition, sensory nerves in the annulus fibrosus and epidural space are not protected from topical interaction with pain mediators induced by decompression surgery. The secondary etiology of sciatica from lumbar disc herniation is sensitization of the nerve root. Sensitization of the nerve root results from a) mechanical compression, b) exposure to cellular pain mediators, and/or c) exposure to biochemical pain mediators. Although decompression surgery reduces nerve root compression, sensory nerve sensitization often persists. These observations are consistent with continued exposure of tissue in the epidural space, including the nerve root, to increased cellular and biochemical pain mediators following surgery. A potential contributor to lumbar back pain (LBP) is stimulation of sensory nerves in the annulus fibrosus by a) cellular pain mediators and/or b) biochemical pain mediators that accompany annular tears or disruption. Sensory fibers located in the outer one-third of the annulus fibrosus increase in number and depth as a result of disc herniation. The nucleus pulposus is comprised of material that can produce an autoimmune stimulation of the sensory nerves located in the annulus and epidural space leading to LBP. The sensory nerves of the annulus fibrosus and epidural space may be sensitized by topical exposure to cellular and biochemical pain mediators induced by lumbar surgery. Annulotomy or annular rupture allows the nucleus pulposus topical access to sensory nerve fibers, thereby leading to LBP. Coverage of the annulus and adjacent structures in the epidural space by absorbable viscoelastic gels appears to reduce LBP following surgery by protecting sensory fibers from cellular and biochemical pain mediators. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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Open AccessReview Preparations and Characterizations of Luminescent Two Dimensional Organic-inorganic Perovskite Semiconductors
Materials 2010, 3(5), 3385-3406; doi:10.3390/ma3053385
Received: 20 March 2010 / Revised: 7 May 2010 / Accepted: 18 May 2010 / Published: 25 May 2010
Cited by 25 | PDF Full-text (1000 KB)
Abstract
This article reviews the synthesis, structural and optical characterizations of some novel luminescent two dimensional organic-inorganic perovskite (2DOIP) semiconductors. These 2DOIP semiconductors show a self-assembled nano-layered structure, having the electronic structure of multi-quantum wells. 2DOIP thin layers and nanoparticles have been prepared through
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This article reviews the synthesis, structural and optical characterizations of some novel luminescent two dimensional organic-inorganic perovskite (2DOIP) semiconductors. These 2DOIP semiconductors show a self-assembled nano-layered structure, having the electronic structure of multi-quantum wells. 2DOIP thin layers and nanoparticles have been prepared through different methods. The structures of the 2DOIP semiconductors are characterized by atomic force microscopy and X-ray diffraction. The optical properties of theb DOIP semiconductors are characterized from absorption and photoluminescence spectra measured at room and low temperatures. Influences of different components, in particular the organic parts, on the structural and optical properties of the 2DOIP semiconductors are discussed. Full article
(This article belongs to the Special Issue Luminescent Materials)
Open AccessReview Of Chains and Rings: Synthetic Strategies and Theoretical Investigations for Tuning the Structure of Silver Coordination Compounds and Their Applications
Materials 2010, 3(5), 3407-3429; doi:10.3390/ma3053407
Received: 16 March 2010 / Revised: 14 May 2010 / Accepted: 17 May 2010 / Published: 25 May 2010
Cited by 36 | PDF Full-text (1729 KB) | HTML Full-text | XML Full-text
Abstract
Varying the polyethyleneglycol spacer between two (iso)-nicotinic groups of the ligand systems, a large structural variety of silver coordination compounds was obtained, starting with zero-dimensional ring systems, via one-dimensional chains, helices and double-helices to two-dimensional polycatenanes. Theoretical calculations help to understand their formation
[...] Read more.
Varying the polyethyleneglycol spacer between two (iso)-nicotinic groups of the ligand systems, a large structural variety of silver coordination compounds was obtained, starting with zero-dimensional ring systems, via one-dimensional chains, helices and double-helices to two-dimensional polycatenanes. Theoretical calculations help to understand their formation and allow predictions in some cases. These structures can be tuned by careful design of the ligand, the use of solvent and the counter ions, influencing also other important properties such as light stability and solubility. The latter is important in the context of biomedical applications, using silver compounds as antimicrobial agents. Full article
(This article belongs to the Special Issue Organometallic Compounds)
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Open AccessReview Prediction of Excitation Energies for Conjugated Oligomers and Polymers from Time-Dependent Density Functional Theory
Materials 2010, 3(5), 3430-3467; doi:10.3390/ma3053430
Received: 10 February 2010 / Revised: 14 March 2010 / Accepted: 18 March 2010 / Published: 24 May 2010
Cited by 3 | PDF Full-text (1151 KB)
Abstract
With technological advances, light-emitting conjugated oligomers and polymers have become competitive candidates in the commercial market of light-emitting diodes for display and other technologies, due to the ultralow cost, light weight, and flexibility. Prediction of excitation energies of these systems plays a crucial
[...] Read more.
With technological advances, light-emitting conjugated oligomers and polymers have become competitive candidates in the commercial market of light-emitting diodes for display and other technologies, due to the ultralow cost, light weight, and flexibility. Prediction of excitation energies of these systems plays a crucial role in the understanding of their optical properties and device design. In this review article, we discuss the calculation of excitation energies with time-dependent density functional theory, which is one of the most successful methods in the investigation of the dynamical response of molecular systems to external perturbation, owing to its high computational efficiency. Full article
(This article belongs to the Special Issue Conjugated Oligomers)

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