Academic literature on the topic 'Codoping'

AbstractTransparent and conducting p-type zinc oxide (ZnO) thin films doped with gallium (Ga) and nitrogen (N) simultaneously were deposited on glass substrates by spray pyrolysis technique. Phase composition analysis by X-ray diffraction confirmed the polycrystallinity of the films with pure ZnO phase. Energy dispersive X-ray analysis showed excellent incorporation of N in the ZnO matrix by means of codoping. The optical transmittance of N monodoped film was poor but got improved with Ga-N codoping and also resulted in the enhancement of optical energy gap. Hole concentration increased with codoping and consequently, lower resistivity and high stability were obtained.

Abstract X-ray-induced photodarkening and its suppression by Ge-codoping were investigated in Al-doped, Dy-doped, and Dy-Al-doped silica glasses. Absorption bands of 4f-4f5d transition of Dy2+ were determined in Dy-Al-doped silica glass fabricated by Si nano-powders as a reducing agent, and it was found that pair generation of Dy2+ and Al-OHC was occurred in X-ray irradiated Dy-Al-doped silica glass. Ge-codoping suppresses the above-mentioned pair generation and instead forms the pair of GEC and GLPC+. A similar suppression effect of Ge-codoping was observed in Al-Ge-doped silica glass, where pair generation of Al-OHC and Al-E′ center was suppressed. To investigate the stability of defects, annihilation processes during thermal annealing were measured. Al-OHC and Dy2+ are destabilized by Ge-codoping in Al-doped and Dy-Al-doped silica glasses, while GEC is stabilized in Al-Ge-doped and Dy-Al-Ge-doped silica glasses. Based on these results, local structure models around Al, Ge, and Dy ions and possible mechanisms of photodarkening were proposed.

Based on the first-principle calculations, we present a study for p-type ZnO doping. The calculated results show that (F, Li) codoping can suppress the formation of interstitial Li because the formation energy of FO-LiZn is lower than that of FO-Lii under O-rich condition. However, it is also found that FO-LiZn codoping could not realize p-type ZnO because FO-LiZn forms a fully passive complex. Interestingly, we further find FO-2LiZn is a stable acceptor that has lower formation energy and shallower transition level under O-rich condition. We expect this study might be helpful for synthesizing good p-type ZnO by controlling (F, Li) codoping.

The effect of cation (Mo or W) and anion (N) codoping in different proportion has been explored to improve the photocatalytic activity of SrTiO₃ under visible light. Codoping in 1 : 2 ratio has been found to be more effective due to reduction in band gap without introducing local trapping center and also for maintaining appropriate band alignment.

The structural and electronic properties of iron-fluorine (Fe-F) and iron-sulfur (Fe-S) codoped anatase TiO2are investigated by first-principles based on density functional theory. Our results show that the formation energy of codoped system is lower than that of single-element doping, which indicates the synergic effect of codoping on the stability of the structure. Codopants introduced impurity gap states resulting in the electron transition energy reduction and thus the visible light absorption observed in the samples. It is concluded that Fe-S should be a better codoping pair because Fe-S codoping introduces extended impurity states resulting in stronger visible light absorption than that of Fe-F codoped compounds. This work gives understanding to the recent experiment and provides the evidence of choosing the more effective co-dopants in TiO2.

By using first principles calculations, we propose a codoping method of using acceptors and donors simultaneously to realize low-resistivity and high carrier concentration p-type ZnS with wurtzite structure. The ionization energy of singleNScan be lowered by introducing theIIIZn-NS(III = Al, Ga, In) passivation system. Codoping method in ZnS (2N, III) has lower formation energy comparing with single doping of N since III elements act as reactive codopants.

A novel reddish orange phosphor CaIn2O4:Sm3+codoped with Zn2+or Al3+ions was prepared by solid state reaction and their luminescence properties were investigated under near ultraviolet excitation. The strategy of Zn2+or Al3+ions codoping was used with the aim to improve the luminescence properties of CaIn2O4:Sm3+, but the concrete effects of the two ions is different. The introduction of Zn2+ions can produceZnIn'defects that favor charge balance in CaIn2O4:Sm3+to facilitate its photoluminescence. The effect of Al3+ions codoping can effectively transfer energy from charge-transfer absorption band to characteristic transition of Sm3+ions, utilizing more energy from host absorption for the photoluminescence of Sm3+ions. Based on these mechanisms, the luminescence intensity of CaIn2O4:0.6%Sm3+was enhanced to 1.59 times and 1.51 times when codoping amount of Zn2+and Al3+ions reached 0.6%. However, the chromaticity coordinates of CaIn2O4:0.6%Sm3+almost did not have any changes after Zn2+ions or Al3+ions codoping; those are still located at reddish orange region. The excellent luminescence properties of CaIn2O4:0.6%Sm3+,0.6%Zn2+and CaIn2O4:0.6%Sm3+,0.6%Al3+demonstrate that they both have potential application value as new-style reddish orange phosphors on light-emitting diode.

We have demonstrated efficient blue organic light-emitting diode with the structure of indium tin oxide/4,4′,4″-tris(N-(2-naphthyl)-N-phenyl-amino)triphenylamine/1,4-bis[N-(1-naphthyl)-N′-phenylamino]-4,4′-diamine/9,10-di(2-naphthyl)anthracene (ADN): 1-4-di-[4-(N,N-di-phenyl)amino]styryl-benzene (DSA-ph) 3 wt%/tris-(8-hydroxyquinoline)aluminum/LiF/Al. Improved efficiencies and longer operational lifetime were obtained by codoping a styrylamine-based dopant BD-3 (0.1 wt%) into the emitting layer of ADN doped with DSA-ph compared to the case of non-codoping. This was due to the improved charge balance and expansion of exciton recombination zone. The better charge balance was obtained by reducing the electron mobility of ADN which was higher than the hole mobility in the case of non-codoping.

Er3+ doped Yb2Ti2O7 nanophosphors by Gd3+ codoping with nominal composition of (Er0.05Yb0.95−xGdx)2Ti2O7 (x = 0, 0.2, 0.4, 0.6, 0.8, and 0.95) have been prepared by sol–gel method. −Er3+–Gd3+ codoped Yb2Ti2O7 was characteristic of a typical face-centered cubic crystal phase, and the unit cell parameter increased linearly with the increase of Gd3+ concentration. Under a 976 nm laser diode excitation, both green and red upconversion emissions were observed and the upconversion emissions were enhanced significantly by Gd3+ codoping, showing the strongest green and red emissions at 80 mol% Gd3+ codoping. The intensity ratio of green to red emissions (Igreen/Ired) increased monotonously with the increase of Gd3+ concentration. The energy transfer between Yb3+ and Er3+ and the variation of local crystal field symmetry of Er3+ by the substitution of Yb3+ by Gd3+ ions led to the improvement of upconversion properties of Er3+–Gd3+ codoped Yb2Ti2O7 nanophosphors.

In this work, doping C and codoping C and N into the Sb2Te3 traditional chalcogenide were investigated to reduce the writing current of the phase-change device using a chalcogenide as the active medium. No face-centered-cubic (FCC) structure was observed in the C-doped Sb2Te3 film, while it appeared after codoping C and N into Sb2Te3. The FCC crystallite size greatly reduced from 6.5 to 3.5–3.8 nm after codoping. In particular, the resistivity of FCC C–N codoped Sb2Te3 was about two orders of magnitude higher than that of Sb2Te3. The effect of the property of the chalcogenide on the writing current of the phase-change device was analyzed by the finite element method. The analysis showed that the writing current of the device using C–N-codoped Sb2Te3 as the active medium can significantly drop to about 1/8 of that of the Sb2Te3 based one.

Most of the topics dealt with in this thesis belong to surface science. The starting point was the fundamental understanding of phenomena at the oxide-gas interface and the effect of its modification. Such knowhow was then used to solve (or, at least, to attempt to solve) issues of critical impact in everyday life: the increasing lifetime of building materials employed in low-impact smart houses; the fouling prevention in electroanalytical sensors for neurotransmitter detection; the unspecialized laboratories accessibility to microlithography, critical to device miniaturization. These challenges might seem not related, but they actually share deep scientific and technological foundations. The physicochemical modification of oxide surfaces, the creation of organic/inorganic hybrids and the exploiting / the enhancing of semiconductor peculiar properties allowed us, starting from the foundation, the realization of proof-of-concept protocols and devices, ready for the pre-commercial development. The Leitmotif of my research was the synthesis and the modification of titanium dioxide surfaces. TiO2 has been the main character in physico, physicochemical and material science researches of the last 50 years. Biocompatibility and low cost make it engaging for many applications. Its (near-UV active) semiconductor features, well known and abundantly investigated by the scientific community, are acquiring central interest also in many markets with the development of self cleaning coatings, windows and asphalts, anti-fogging mirrors and self-sterilizing surgery rooms and instrumentations. New generation batteries and solar cells are going to be developed as commercial prototypes. One of the biggest challenges in the titania fundamental research is the enhancement of activity in the solar spectrum. First, the most recent aspects in titania doping and promotion were touched. While, in the last twenty years, great effort has been made in the mono-atomic doping of titania and in the understanding of the influence of the dopant position in the titania lattice and its electronic behavior, the most recent literature describes the co-promotion of the material by two (or more) atoms doping. The metal/non-metal codoping seems especially promising; the synergetic effect of the two atoms in the TiO2 lattice was both theoretically and experimentally proved. In this contest, the N/Nb codoping was analyzed, investigating the effect of the atoms in the lattice from morphological (surface area, porosity and crystallographic structure) and electronic point of view (EXAFS, UV-Vis absorption and EPR analyses). N/Nb codoping was compared with N/Ta co-doped samples, synthesized by two different procedures. The photoactivity of the two sample families was tested by a model reaction (the degradation of ethanol, throughout acetaldehyde intermediate) both under UV and solar simulated irradiation. Then, a different approach in the modification of surfaces was tested. The assembly of organic/inorganic hybrids was tested; thanks to the formation of organic mono- or multi-layers at the surface,they can tune the chemistry, the polarity and the adhesion properties of the interface. Siloxanes were used as active agents, thanks to their compatibility with oxide materials and, especially, for the ability to self-assemble at the surface to form a monolayer. Siloxanes are able to react with the -OH groups at the surface, chemisorbing and polymerizing at the interface in such a way to form a monolayer with tunable functionalities. Many different silanes were tested and their dipole momenta were related to their wettability properties. Such siloxanes chemisorb strongly both from the gas phase and the liquid phase. Their reactivity, both on smooth and rough surfaces, was tested vs the temperature of functionalization in gas phase. Many characterization techniques were adopted to understand the behavior of such molecules from a molecular point of view: magnetic (solid state NMR), microscopic (SEM, TEM, AFM), optical and electrochemical (CV and EIS). The science of adhesion and wettability was also adopted for the development of superhydrophobic coatings. Titanium dioxide particles with engineered morphology were used as the best candidate to create superhydrophobic/superhydrophilic patch-wise surfaces, exploiting their photoactivity (photolithograpy). The core of the thesis was the synthesis, modification and application of transparent photoactive thin films. A procedure for the synthesis of smooth, transparent and photoactive TiO2 thin layers was developed, and used to produce highly applicative devices and protocols. Such synthetic strategy is highly tunable and reproducible; the obtained films are robust and active and, most of all, require simple instrumentation (sol-gel procedure), which is highly appealing for the market. The films were properly characterized both form the morphological/mechanical and photochemical point of view. Apart their transparency and their thickness, the films were highly crystalline (pure anatase phase). Such procedure was firstly designed as a proof-of-concept for self-cleaning windows, but, thanks to its versatility and the high activity of the films, it leads the path towards highly applicative procedures and devices. The smoothness and the photoactivity brought me to the field of photolithograpy, especially in the direction of microlithography. The high activity of the titania allowed the use of safe and low-energetic lamps. No collimation was required to obtain a resolution lower than 5 µm. First of all, I tested the lithography on siloxane monolayer films, as a proof-of-concept of resolution and efficiency. But siloxanes, as many other self-assembled monolayer molecules, can be the pillars for 3D fabrication. Such monolayers were used as polymerization initiators for polymer brushes. If the initiators of polymerization are patterned, patterned polymer brushes will be obtained. That was the first report of polymer-brushes lithography exploiting the photoactivity of TiO2. Remote photocatalytic lithography makes this procedure extremely versatile. Exploiting the remote photocatalysis, in principle, any material can be used as a support for patterned polymer brushes growth (provided that the initiator are able to graft the surface). The developed protocol for the synthesis of TiO2 thin films was also used to design and engineer complex electrodes for cyclovoltammetric analyses of biological samples. Electrochemistry seems to be the best candidate for the development of an analytical option with sensitivity comparable with present analytical procedures but reduced time-per-analysis and cost. Unfortunately, catecholamines chemisorb and polymerize on metal and oxide electrodes quickly, making the device useless. Covering the electrode by a homogeneous, nano-porous thin layer of titania makes the surface photoactive. That is the first example in literature of self-cleaning nano-engineered electrodes for cyclic voltammetry. After the detection, also in simulated human serum and liquor, a fast and simple irradiation of the device, under non-hazardous UV-A lamp, degrades all the fouling on the surface without altering its features. The sensor, after each UV treatment, recovers its pristine performances, with full recovery in terms of selectivity and sensitivity. Irradiation trials were also performed directly in the analytical mixture, as a proof of concept for on-site application. Modern era requires flexible and light materials for the building industry. Polymers are acquiring more and more interest thanks to their increasing performances and their smart properties. The drawbacks of such materials are connected to the low resistance to the UV light, the softness and the difficulties in cleaning procedure. The use of organic/inorganic hybrid, or better the coverage of plastic materials with an oxidic thin layer, can solve many of these problems, lengthening the lifetime of such materials. If the covering oxide is also photoactive, the material can be self-cleaned when exposed to solar light. That is a big chemical challenge, because of many synthetic problems. Two different approaches were tested to solve this relevant issue. On one side, the hydrophobicity of ionic liquid modified SPES (sulfonated polyether sulfone) was combined with designed morphological features to confer superhydrophobicity. On the other side, the polymeric surface was covered with a transparent titania layer active in the near UV-region, able to mineralize organic molecules chemisorbed at the surface. Eventually, a different approach to modify oxidic (and not only) surfaces is the creation of a homogeneous layer of Ag nanoparticles by an innovative microwave procedure. That simple and accessible strategy allowed us to produce plasmonic surfaces (thanks to the dimension and the homogeneity of the Ag particles) with countless applications. The layer was shown to be a very active substrate for surface enhancement Raman spectroscopy (SERS). Thanks to the versatility of the synthetic method, all shapes and dimensions can be covered. That makes it a perfect candidate for the production of new generation of SERS sensors. The sensitivity towards molecules of environmental and biomedical interest was proved.

The luminescence properties of erbium-doped silicon with fluorine as a codopant have been studied. Erbium in silicon is seen as a very promising way to obtain light emission from silicon. With the aim of improving understanding of the role of fluorine in the Er:Si system, erbium and fluorine were implanted into silicon substrates and annealing was carried out to regrow the damaged silicon. The material properties were studied using Rutherford backscattering spectrometry and correlated with the luminescence properties, which were investigated using photoluminescence spectroscopy. Frequency resolved photoluminescence spectroscopy was used to provide information on the lifetimes associated with the luminescence process. This is the first time this technique has been applied to this system. Erbium has been incorporated in good quality crystal Si at concentrations up to 1020 cm-3. This is two orders of magnitude greater than the estimated solid solubility and equals the highest reported concentration for erbium in crystalline Si. For all but the highest fluorine dose employed, regrowth of the silicon took place to at least within 250 A of the surface. Fluorine doses of 5x1016 cm-2 appeared to disrupt the epitaxial regrowth of the silicon and very weak photoluminescence was obtained. At the lowest fluorine dose employed (1015 cm-2) segregation of the erbium occurred into two regions consistent with the formation of a buried amorphous layer following the original implants. In high resolution photoluminescence spectra, lines were observed which have been identified as due to isolated interstitial erbium. A thermally unstable interstitial lattice site of hexagonal symmetry was also identified, as well as lines originating from implantation related defects. All the samples exhibited luminescence whose decay could be represented by two lifetimes, both of which were strong inverse functions of temperature, and whose values at 75 K were approximately 200 mus and 700mus. An idea for a temperature sensor is presented which could be realised using current implant technology.

Dans le cadre des recherches sur des dispositifs laser compacts pouvant etre pompes par diodes, ce memoire decrit le developpement d'une nouvelle technique d'elaboration de lasers guides d'onde, l'epitaxie en phase liquide. Cette technique a ete appliquee a la croissance de couches minces monocristallines de yag dope neodyme et ytterbium sur des substrats de yag non dope. Afin d'obtenir des guides de bonne qualite, nous avons defini les conditions de croissance des couches et montre l'interet de la croissance d'une surcouche de confinement. Deux co-dopages ont ete etudies en supplement a l'ion actif: gallium pour controler l'indice optique des couches, lutetium pour controler leur parametre cristallin. La determination du coefficient de segregation des divers dopants a requis le developpement d'un modele qui prend en compte l'evolution des bains au cours du temps. Nous avons mesure l'augmentation d'indice due a chaque dopant et propose un mecanisme expliquant cette augmentation. La caracterisation spectroscopique des couches a indique que les ions actifs ont les memes proprietes que le materiau massif de meme composition. La caracterisation laser a montre des pertes par propagation tres faibles (environ 0,1 db/cm), comparables a celles du materiau massif. Pour la transition laser a 1064 nm du neodyme, nous avons demontre l'effet laser pour une puissance absorbee au seuil de 700 w et mesure un rendement differentiel de 40% en pompage par diode, pour un seuil de 14 mw. Pour des transitions laser quasi-3 niveaux, une diminution significative du seuil par rapport a une configuration non guidee a ete obtenue: a 946 nm dans un guide dope neodyme, a 1029 nm dans un guide dope ytterbium en pompage par barrette de diode 1w. Un rendement differentiel de 80% a egalement ete mesure dans un guide dope ytterbium emettant a 1048 nm

Des amplificateurs sont necessaires a la regeneration du signal dans les lignes de transmission a grandes distances. Les amplificateurs optiques permettent de conserver la bande passante des systemes de transmission. Ils sont d'ores et deja disponibles commercialement sous forme de fibres dopees erbium, mais occupent un volume important et ne permettent pas la combinaison de plusieurs fonctions. Une alternative peut etre envisagee en transposant les principes des fibres dopees erbium a des amplificateurs integres. Un marche potentiel de grande ampleur existe pour de tels composants. Cette these est une premiere tentative de fabrication de tels amplivateurs par le procede sol-gel, dans une matrice vitreuse de sio#2-tio#2. Une premiere partie pose la problematique de l'etude et expose les parametres a optimiser : il faut augmenter le temps de vie du niveau metastable et la concentration d'auto-extinction des ions erbium, diminuer l'attenuation des guides, et controler l'epaisseur et l'indice des depots sol-gel. Dans une deuxieme partie, le processus de fabrication des guides est decrit et chaque etape du processus est analysee de facon a etudier son influence sur les parametres a optimiser. Dans la troisieme partie, on montre comment le processus de fabrication est oriente pour obtenir la meilleure qualite de guide possible. Les resultats obtenus sont presentes. Une etude preliminaire a ete effectue avec du neodyme. Une concentration d'auto-extinction de 1% atomique en neodyme et un temps de vie de fluorescence de 375 s a faible concentration sont atteints dans des guides plan. Avec l'erbium, la concentration d'auto-extinction est de 0. 6 % atomique, et un temps de vie de 6 ms est trouve a faible concentration. Une premiere mesure de gain sur des guides canaux donne 3 db de gain interne a 1531 nm. Le gain est constant sur 25 nm. Le procede sol-gel est une alternative aux technologies deja existantes (fhd et pecvd) pour l'integration d'amplificateurs optiques sur silicium. Ses capacites a fournir des amplificateurs de bonne qualite devraient etre mises en evidence par des etudes complementaires. Des solutions sont proposees.

Etude de la faisabilite de cet imageur utilisant, comme principe d'acquisition de l'image x, l'effet gudden-pohl, phenomene de luminescence retarde stimulee electriquement (lse). Seuls zns et cds dopes par cu, au ou ag donne l'effet lse adequat apres une phase de sensibilisation. Variation de la luminescence en fonction de la dose de rayons x, du champ electrique, de la temperature, du dopage, etc. Modelisation de l'effet lse: l'enregistrement de l'image se fait par piegeage de trous sur des accepteurs dans la couche d'appauvrissement superficielle, la recombinaison radiative se produisant avec ces trous lorsque le champ electrique applique abaisse la barriere de potentiel superficielle. Elaboration d'une maquette en vue du developpement d'un imageur mammographique numerique

Etude par une methode d'excitation selective sur cdcsbr::(3) dope par nd**(3+) et liyf::(4) dope par nd**(3+), pr**(3+) et ho**(3+), er**(3+), tm**(3+); etude de la redistribution de l'excitation optique entre deux ions constituant une paire, chemins de desexcitation. Mise en evidence du role dominant de l'interaction de superechange dans les processus de transfert

La methode est utilisee pour l'etude de la densite d'etats dans la bande interdite du silicium amorphe hydrogene et sur cdin::(2)s::(4). La caracterisation des niveaux ayant des energies d'ionisation thermique entre 0,1 ev et 0,9 ev, le modele de transfert de charge decrivant l'effet photorefractif et l'evaluation du niveau de recombinaison, sont faits dans le materiau photorefractif. Les effets du dopage (fer) et du codopage (fer, vanadium) sur les niveaux sont consideres. Le centre responsable de la capture d'electrons est aussi etudie par absorption optique et photoconductivite photoinduites. Les resultats s'accordent avec ceux des mesures de photorefractivite

碩士
國立東華大學
材料科學與工程學系
93
The object of the thesis is the synthesis of visible-light responsed photocatalysts. WOx codoping on nitrogen-doped titanium oxide（WOx- TiO2-xNx）was synthesized by RF magnetron sputtering. XRD, Raman, XPS were used detect the film structure crystallinity and surface composition. SEM used to observe the surface morphology and roughness. The UV-Vis. spectrophotometer was used to analyse the absorption spectra of the films. The photocatalytic activity was evaluated by the degradation methylene blue and photoreduction of silver-ions under visible light. The results indicate that the TiO2-xNx films are in anatase phase, and the WOx- TiO2-xNx films still main anatase structure. The WOx- TiO2-xNx films of absorption onset extend well into the visible regionat at λ~ 550 nm. TiO2 film shows nearly no photoactivity under visible light. However WOx- TiO2-xNx film had higher photoactivity with the rate constant（k）about 0.084 hr-1 under visible light. The hydrophilic property was characterized by the water contact angle variation from 48° to 6° within 80 mins.

碩士
國立交通大學
顯示科技研究所
99
In this study, through doping of two different near-infrared (NIR) materials in organic photodiodes, the absorption of the device was extended to 1200 nm. Meanwhile, it effectively promoted the responsivity of the device by the process of photomultiplication. This mechanism could be attributed to trapping of electrons, originating from the photogenerated electron/hole pairs, at the NIR dyes. The trapped carriers could induce an electric field and decrease the injection barrier, eventually leading to the injection of holes from the external circuits and high photocurrent multiplication phenomenon occurred at reverse bias conditions. Because codoping of two different NIR dyes , we have successfully fabricated highly sensitive polymer photodetectors exhibiting broad spectral responses ranging from the ultraviolet to the NIR region.

碩士
國立成功大學
環境工程學系
103
Human spend 85% or more of their lives in indoor. The indoor environment play an important role that can affect human health. So indoor air quality has received much attention. Many volatile organic compounds (VOCs) are major air pollutants in the indoor air, toluene, as one of the most predominant VOCs, is widely applied to rubber, paint, ceiling, disinfectant, tackiness agent and chemical reactants. However, toluene has high toxicity, carcinogenicity and long persistence at indoor environment. So removal of toluene is an important task in the indoor air quality. Traditional methods of reducing indoor air pollutant include passing it through activated carbon, increasing the air exchange rate, controlling pollutant source, photocatalytic oxidation process (PCO). Among them, PCO is a promising technology for VOCs removal since it has more advantages compared to other traditional methods. Specifically, PCO is degrading VOCs into nontoxic water vapour and carbon dioxide. Semiconductors used as photocatalysts are capable of removal most VOCs effectively. Among them, titanium dioxide is known as the most popular semiconductor because it is cheap, safe, stable with strong oxidation power and chemical and biological inertness. However, the band gap energy of titanium dioxide is 3.0 to 3.2 eV resulted that titanium dioxide displays very little photocatalytic activity under visible light. On the other hand, the solar light reached to the ground of earth only has 5% energy in UV light. Therefore, to enhance the solar efficiency of titanium dioxide under solar light, it is necessary to modify it to facilitate visible light absorption. In this study, TiO2, sulfur doped TiO2 and sulfur-zinc codoped TiO2 were prepared by a sol-gel method. The photocatalytic decomposition rate of toluene under visible light was expected to increase by doping sulfur and codoping sulfur-zinc. To analyze the physical and chemical characteristics of photocatalysts we used TGA, XRD, SEM, EDS, Mapping, TEM, UV-Visible spectroscopy, FT-IR, XPS and ICP-MS, respectively. Therefore, we can know the crystalline phase, particle size, absorbance spectrum, band gap, and chemical bonding, which will help us to understand the decomposition rate of toluene. The results of XRD, SEM and TEM of the photocatalysts show that codoped S and Zn can reduce the crystalline size and all photocatalysts are anatase phase structure. The XPS results of codoped S and Zn photocatalyst. Show that Ti exists as Ti4+, O as O2-, S as S6+, Zn as Zn2+ on the surface crystal lattices. The activity of photocatalysts was determinated by the measurement of toluene degradation under visible light. According to the results of activity test, S5Zn0.01/TiO2 photocatalyst with choser for further studies. With the operation parameter tests, the results show that the lower toluene concentration and relative humidity could increase toluene conversion. However, lower temperature and retention time would reduce conversion. By fitting with a Langmuir-Hinshelwood model 4, the result shows that Kw is larger than KA, and it also displays that adsorption ability of H2O is large than toluene. The r rises as the temperature growing. The photocatalytic active energy is 78.10 kJ/mol. In S5Zn0.01/TiO2 photocatalytic degradation of toluene under visible light process, the reaction intermediates and products were detected in the gas phase and on the photocatalyst surface, intermediates as benzaldehyde, benzyl alcohol, benzoic acid, acetone, butadiene and acetic acid by FT-IR, products as CO2 and H2O by FT-IR.

This article discusses the structural, electronic, magnetic, and transport properties of carbon-fullerene-based polymers. In particular, it examines the defect-induced ferromagnetism of the C60-based polymers and its analog in the case of non-traditional inorganic materials. It first reviews the computational methods currently used in the literature, highlighting the pros and cons of each one of them. It then considers the defects associated with the ferromagnetism of the C60-based polymers, namely carbon vacancies, the 2 + 2 cycloaddition bonds and impurity atoms, and their effect on the electronic structure. It also evaluates the effect of codoping and goes on to describe the electronic, magnetic and transport properties of the rhombohedral C60-polymer. Finally, it looks at the origin of magnetic coupling among the magnetic moments in the rhombohedral C60-polymer and provides further evidence for the analogy between the magnetism of the rhombohedral C60-polymer and zinc oxide.

Recent works have suggested that the defect induced magnetism in Diluted Magnetic Semiconductors (DMSs), Transition Metal Oxides (TMOs) and related materials is facilitated and enhanced by codoping and the synergistic action between the codopants. In the present work we demonstrate that the proposed defect synergy is the result of the interplay among correlated spin-polarization processes which take place in a successive way in neighborhoods centered at the codopants and include their first nearest neighbors. These processes result in a reduction in the superexchange coupling which in turn causes an enhancement in the ferromagnetic coupling (FMC) among the magnetic dopants. The proposed FMC is demonstrated using ab initio calculations of the electronic properties of codoped ZnO, GaN and TiO2.

In recent years, water pollution has become one of the major challenges faced by humans because of consistent rise in population and industrial activities. Water pollution due to discharge from cosmetics and pharmaceutical wastes, organic dyes, and heavy metal seen as carcinogens has the potential to disrupt hormonal processes in the body. Different approaches such as chlorination, aerobic treatment, aeration, and filtration have been deployed to treat wastewaters before being discharged into the streams, lakes, and rivers. However, more attention has been accorded to treatment approaches that involve use of nanomaterial due to non-secondary pollution, energy efficiency, and ease of operation. Titanate-based perovskite (TBP) is one of the most frequently studied nanomaterials for photocatalytic applications because of its stability and flexibility in optical band-gap modification. This chapter provided an overview of basic principles and mechanisms of a semiconductor photocatalyst, and current synthesis techniques that have been used in formulating TBP nanomaterial. The effect of reaction conditions and approaches such as doping, codoping, composites, temperature, pH, precursor type, surface area, and morphology on surface defects and optical band-gap energy of TBP nanomaterial was highlighted. Importantly, the impact of surface defects and optical band-gap energy of TBP on its photocatalytic activities was discussed. Finally, how to enhance the degradation efficiency of TBP was proposed.

The lasing transition between the 4I11/2 and 4I13/2 of Er3+ in YAG is self-terminating due to the significantly longer lifetime of 4I13/2. This paper describes the codoping of Er:YAG with Eu and Tb as deactivator ions to reduce this undesirable effect by energy transfer between the 4I13/2 of Er3+ and the codopant ions. Unique grouping of levels in Eu3+ and Tb3+ provide numerous levels between 4I13/2 and the ground state for fast multiphonon relaxation but none near 4I11/2. Crystals of 16% Er:YAG codoped with different Eu and Tb concentrations were grown by the laser-heated pedestal growth technique for measuring lifetimes of excited Er3+ ions. We found that with both Eu and Tb, doping at ~1% increased the ratio of upper to lower state lifetimes from 0.02 to better than 0.3. Higher doping did not increase this ratio as quenching of 4I11/2 became significant. This is likely due to cross relaxation involving ground state ions of the codopant. Although unable to achieve a ratio of unity and above, codoping Er:YAG should still lead to improvement in pulsed laser performance.

There has been a surge of interests in photosensitive fibre gratings in recent years chiefly due to their ease of fabrication and numerous application. Although very large photo-induced index changes have been achieved in pure germanosilicate fibres, an enhanced photosensitivity is desirable to enable gratings to be written with ease and with much cheaper laser source. Stronger photosensitivity also opens up many new applications. Boron-codoping in germanosilicate fibres has been reported to give a much enhanced photosensitivity comparing to that in pure germanosilicate fibres [1], but gratings in those fibres have a much poorer high temperature stability and the B-codoping can also give rise to excessive loss at the important telecommunication window of 1.55 μm. Some post-fabrication techniques have also been devised, i.e. H2/O2 flame-brushing of a germanium doped fibre [2] and Low-temperature hydrogen loading [3], but they are very time-consuming and there are also large induced losses [3]. In this paper, we report on enhanced photosensitivity in Sn-codoped germanosilicate fibres. The gratings in the Sn-doped fibres also have a much improved high temperature stability than those in B-codoped fibres. Unlike B-codoping, Sn- codoping does not introduce significant loss at the important telecommunication window of 1.55 μm.