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The surface of any binary or multi-component nanocrystal has imperfections and defects. The number of surface defects depends both on the nature of the nanomaterial and on the method of its preparation. One of the possibilities to confine the number of surface defects is the epitaxial growth of the shell, which leads to a change in the physical properties while maintaining the morphology of the core. To form a shell of the desired thickness, an accurate calculation of the amount of its precursors is substantial to avoid the appearance of individual crystals consisting of the shell material. This study aimed to develop an effective calculation method for the theoretical amount of precursors required for the formation of a ZnS shell on the surface of a Cd0.25Zn0.75Se core, followed by the practical implementation of theoretical calculations and characterization of the prepared nanomaterials. This method allows the complete control of the masses and volumes of the initial reagents, which will in turn prevent undesirable nucleation of nuclei consisting of the shell material. In the synthesis of Cd0.25Zn0.75Se/ZnS core/shell quantum dots (QDs), the sources of chalcogens were substituted seleno- and thioureas, which are capable of not only supplanting modern toxic sources of sulfur and selenium but also allowing one to perform the controlled synthesis of highly photoluminescent QDs with a low number of surface defects. The result of this shell overcoating method was an impetuous augmentation in the photoluminescence quantum yield (PL QY up to 83%), uniformity in size and shape, and a high yield of nanomaterials. The developed synthetic technique of core/shell QDs provides a controlled growth of the shell on the core surface, which makes it possible to transfer this method to an industrial scale. Povrch jakéhokoliv binárního nebo multikomponentního nanokrystalu má nedokonalosti a defekty. Množství povrchových defektů závisí jak na druhu nanomateriálu, tak i na metodě jeho přípravy. Jednu z možností, jak omezit množství povrchových defektů je epitaxní růst vrstvy, který vede ke změně fyzikální vlastností, ale zároveň dochází k zachování morfologie jádra. Pro vytvoření obalu zamýšlené tloušťky je nezbytné provést přesné kalkulace množství prekurzoru, aby bylo zároveň zabráněno vzniku nových individuálních krystalů, které obsahují pouze materiál obalu. tato studie je zaměřená na vyvinutí efektivních metod kalkulací množství prekurzoru nezbytného pro formování obalu ZnS na povrchu Cd0.25Zn0.75Se jádra, následované praktickou implementací teoretických kalkulací a charakterizací připraveného nanomateriálu. Tato metoda umožňuje kompletní kontrolu nad množstvím a objemem vstupních reagentů, což má pak za následek prevenci nežádoucích nukleací materiálu obalu. Během syntézy core/shell kvantových teček Cd0.25Zn0.75Se/ZnS bylo použito různých zdrojů chalkogenů na bázi seleno- a thiomočovin, které jsou schopné nejen nahradit moderní toxické zdroje síry a selenu, ale i umožňují provést kontrolovatelnou syntézu vysoce luminiscenčních kvantových teček s malým množstvím povrchových defektů. Výsledkem této obalové metody je výrazné vylepšení fotoluminiscenčního kvantového výtěžku (až 83%) a uniformity velikosti, tvaru a vysokého výtěžku nanomateriálu. Vývoj syntézní techniky core/shell kvantových teček poskytuje vysoce kontrolovatelnou metodu růstu obalu na povrchu jádra, což ji dělá vhodnou pro transfer na průmyslovou aplikační úroveň.

This paper presents an effective hydrothermal route to decorate various types of anodic 1D TiO2 nanotubes (TiO2 NTs) with magnetite nanoparticles (Fe3O4 NPs), yielding a magnetically guidable and a...

Semiconductor quantum dots (QDs) have attracted great attention due to their unique optical and chemical properties. An increasing demand for size and shape uniformity of QDs, high quantum yield (QY) and photochemical stability can be resolved by synthetic methods. Here we report a study of the effect of the precursor ratios within the synthesis of a series of Cd-Zn-S QDs. Trisubstituted thiourea (N-phenylmorpholine-4-carbothioamide) as a new and environmentally friendly source of sulphur in the synthesis of Cd0.2Zn0.8S QDs (Cd, Zn : S molar ratios = 1 : 0.5; 1 : 1; 1 : 1.5; 1 : 2; 1 : 2.5) and CdxZn1-xS QDs (wherex= 0.1; 0.25; 0.5; 0.75; 0.9) has been investigated. It was determined that an increase in the molar ratio of trisubstituted thiourea to metals leads to the growth of QDs and as a consequence, to a small emission red shift in the visible region of the spectrum. However, no significant changes in the elemental ratio in the material were detected. It was found that with an excess of trisubstituted thiourea taken to the reaction, oleylamine (OAm) as a co-ligand replaces linoleic acid from the protective shell of the QDs. In the case of an increase of Cd content in the CdxZn1-xS QDs, a significant shift in the emission to the red region of the spectrum was observed with an increase in the size of the QDs while their shape was unchanged. Based on the XRD data, a gradual transition from a cubic to a hexagonal crystal structure was detected. The high quantum yield (70%), the narrow photoluminescence (PL) signal (FWHM < 31 nm) and the size uniformity of the obtained nanomaterials are promising features for production of highly sensitive sensors and LEDs. Polovodičové kvantové tečky (QDs) přilákaly velkou pozornost díky jejich unikátním optickým a chemickým vlastnostem. Rostoucí požadavky pro velikostní a tvarovou uniformitu QDs, vysoký kvantový výtěžek (QY) a fotochemická stabilita můžou být společně vyřešeny použitou syntetickou metodou. V tomto článku popisujeme efekt poměru prekurzorů během syntézy sérií QDs v systému Cd-Zn-S. Tri-substituovaná thiomočovina (N-feylmorfolin-4-karbotioamid) byla použita jakožto nový a enviromentálně příznivý zdroj síry pro syntézu kvantových teček Cd0.2Zn0.8S (Cd, Zn : S molární poměr = 1 : 0.5; 1 : 1; 1 : 1.5; 1 : 2; 1 : 2.5) a CdxZn1-xS Q (kde x = 0.1; 0.25; 0.5; 0.75; 0.9). Bylo zjištěno, že nárůst molárního poměru tri-substituované thiomočoviny vůči kovům vede nárůstu velikosti QDs a jakožto důsledek i k malému červenému posunu v jejich emisním spektru. nebyly však detekovány žádné výrazné změny v atomárním poměru materiálu částic. Dále byo zjištěno, že s rostoucím nadbytkem tri-substituované thiomočoviny v reakci dochází nahrazování linoleové kyseliny v ochranné slupce QDs za oleylamin (OAm). V případě nárůstu obsahu Cd v částicích CdxZn1-xS dochází k výraznému posunu emise do červené oblasti spektra spojeného s nárůstem velikosti částic, avšak změna jejich tvaru nebyla pozorována. Data z XRD potvrzují postupný přechod kubické krystalické struktury částic směrem ke struktuře hexagonální. Vysoký kvantový výtěžek (70%), úzké fotoluminiscenční spektrum (FWHM < 31 nm) a uniformita získaných nanočástic jsou slibnými vlastnostmi pro produkci vysoce citlivých senzorů a LED diod.

The paper reports on ≈1.5 μm Stokes photoluminescence (PL) emission and upconversion photoluminescence (UCPL) emission in the visible and near-infrared spectral region in Er3+-doped Ge25Ga8As2S65 chalcogenide glasses at pumping wavelengths of 980 and 1550 nm. The ≈1.5 μm PL emission spectra are broadened with increasing concentration of Er ions which is discussed in terms of radiation trapping and UCPL dynamics affecting the Er3+: 4 I 13/2 level lifetime. The UCPL emission was observed at ≈530, ≈550, ≈660, ≈810 and ≈990 nm and its overall intensity as well as red-to-green UCPL emission intensity ratio increases with increasing Er concentration. To explore the UCPL dynamics we measured double logarithmic dependency of green (≈550 nm) and red (≈660 nm) UCPL emission versus pump power at pumping wavelength of 975 nm. Moreover, we measured quadrature frequency resolved spectroscopy (QFRS) on green UCPL emission (≈550 nm) using 975 nm pumping wavelength and various excitation powers. The QFRS spectra on green UCPL were analyzed in term of QFRS transfer function for three-level model from which we deduced energy transfer upconversion rate w 11 (s−1) originating from Er3+: 4 I 11/2, 4 I 11/2→4 F 7/2, 4 I 15/2 transitions.

Quite recently, nanosized rare-earth (RE) fluorides have been gaining importance due to their ability to form nanocomposites that are capable to absorb ionizing radiation. The efficiency of these materials may vary under the influence of external factors and under the growing conditions of nanocrystals. In this paper a novel effective approach to the synthesis of CeF3 nanocrystals (NCs) with a high yield of the desired material was proposed. The developed approach allows different modifications within the synthesis, thereby making it possible to change the growth conditions of QDs. The main exchange reaction between cerium oleate and ammonium fluoride was carried out in a non-coordinating solvent 1-octadecene (ODE) diluted with an excess of oleic acid (OA). The influence of the reaction temperature on the nucleation and the formation of a nanocrystals was presented. The possibility of introducing Tb3+ (1-5%) into nanosized CeF3 at one of the lowest reaction temperatures (180 degrees C) was also studied. The introduction of Tb3+ into the CeF3 crystal lattice led to changes in the nanocrystal's structure, an increase in their size and also to the expected changes in the photoluminescence (PL) spectra. The prepared CeF3 and CeF3:Tb QDs were well dispersible in low-polar media, which makes them promising candidates for the role of active agents or wavelength shifters in the matrix of polymer scintillators. V nedávné době došlo k nárůstu významu nanokrystalů fluoridů dopovaných vzácnými zeminami díky jejich schopnosti formovat nanokompozity absorbující ionizující záření. Účinnost těchto materiálů se může lišit vlivem externích faktorů a podmínkami během růstu těchto nanokrystalů. V této práci prezentujeme nový přístup k syntéze nanokrystalů CeF3 s vysokým výtěžkem zamýšleného materiálu. Vyvinutý přístup umožňuje různou modifikaci během syntézy, a tedy ho dělá vhodným pro změnu růstových podmínek kvantových teček. Hlavní výměnná reakce mezi oleátem ceria a fluoridem amonným byla prováděna v nekoordinovaném rozpouštědle 1-oktadecenu (ODE) rozpuštěném v nadbytku olejové kyseliny (OA). Vliv reakční teploty na nukleaci a formování nanokrystalů jsou dále prezentovány v této práci. Byla taktéž studována možnost vnesení Tb3+ iontů (1-5%) do nanočástic TbF3 za jedné z nejnižších použitých reakčních teplot (180°C). Vnesení Tb3+ do CeF3 krystalové matrice vedlo ke změnám struktury nanokrystalu, nárůstu jejich velikosti a také k očekávané změne ve fotoluminiscečních spektrech. Připravené kvantové tečky CeF3 a CeF3:Yb byly dobře dispergovatelné v nízkopolárním mediu, což je dělá nadějnými kandidáty pro aktivní prvky pro změnu vlnových délek v matrici polymerních scintilátorů.

Solid solution AgInS2-ZnS nanostructures were prepared by reacting (Z)-1- (octadec-9-enyl)-3-phenylthiourea and 1-dodecanethiol with the corresponding metal linoleates. The combination of sulfur sources in modified ratios, which individually do not lead to significant results, resulted in the successful formation of nanorod-shaped heterostructures. The effect of sulfur source ratios on the structure, morphology, and optical properties of yellow-red emitting nanocrystals was systematically studied by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDS), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) analyzes. Nanocomposite materials based on polyvinyl toluene co-divinylbenzene (PVT-DVB) were investigated for each of the resulting nanostructures. It was demonstrated that even traces of nanomaterial (similar to 0.1 wt. %) provide a high photoluminescence quantum yield (PL QY up to 61.5%) of prepared nanocomposites. Pevné roztoky nanostruktur AgInS2-ZnS byly připraveny reakcí (Z)-1- (octadec-9-enyl)-3-fenylthimočoviny s odpovídajícími kovovými linoleáty. Kombinace zdrojů síry v modifikovaných poměrech, které samostatně nevedly k významným výsledkům, měly za následek úspěšnou syntézu heterostruktur ve formě nanotyčinek. Efekt poměrů různých zdrojů síry na strukturu, morfologii a optické vlastnosti žlutě-emitujících nanokrystalů byl systematicky studován metodami rentgenové difrakce (XRD), prvkové analýzy (EDS), rentgenové foto-elektronové spektroskopie (XPS) a skenovací transmisní elektronové mikroskopie (STEM). Nanokompozitní materiály založené na polyvinyl toluen co-divinylbenzenovém polymeru (PVT-DVB) byly studovány na všech připravených nanostrukturách. Bylo potvrzen, že i pouze stopy syntetizovaných nanomateriálů (cca. 0.1 hm.%) poskytnuly vysoký fotoluminiscenční výtěžek připravených nanokompozitů (až 61.5%)

The presented study shows how the incorporation of silver changes the structure and physical properties of chalcogenide glass (GeS2)50(Sb2S3)50. Nine samples with silver content (0–25 at. %) were studied to give a detailed picture. The structure and its changes were analyzed by Raman spectroscopy. The medium range order of the (GeS2)50(Sb2S3)50 glass was identified. The structural motif of interconnected SbS3/2 pyramids is the doorway for the silver incorporation in the (GeS2)50(Sb2S3)50 glass. The material hardness is significantly increased by up to 26% due to silver addition. The ability of silver to fill cavities in a glass is responsible for the observed hardness increase. Electronic properties and silver ion mobility were examined by impedance spectroscopy and radioactive tracer diffusion. The purpose of the presented study is to give an instructive description of how silver change the structure of the studied chalcogenide glass and give a complex feeling of how the silver changes its physical properties.

We report on the Er3+ ↔ Ho3+ optical interaction on the 1.2 and 1.5 µm near-infrared and visible upconversion photoluminescence in Er3+/Ho3+-co-doped GeGaS glasses at pumping wavelength of 980 nm. Since the 980 nm pumping wavelength is off resonance for Ho3+ intra-4f electronic transitions, we have utilized the Er3+ sensitization with observed efficient Er3+ → Ho3+ energy transfer. As a result, the Ho3+ 1.2 µm emission in Er3+/Ho3+-co-doped GeGaS glass has been notably improved while the intense Er3+ 1.5 µm emission has been maintained. The visible upconversion photoluminescence has been observed at 530, 550 and 660 nm and was assigned mainly to intra-4f electronic transitions within Er3+ ions. The overall upconversion photoluminescence intensity significantly increases by addition of Ho3+ ions into GeGaS:Er glass which may be explained by energy transfer processes between Er3+ and Ho3+ ions leading to population of the Er3+ upper energy levels. The Ho3+ 1.2 µm and Er3+ 1.5 µm emission has much potential in telecommunication while the intense visible upconversion photoluminescence in sensing.

We investigated the physicochemicаl properties, structure and optical properties of the Ge25Ga9.5Sb0.5S65: Er3+/Yb3+ glasses. The Judd-Ofelt theory was used to calculate the intensities of the intra-4f electronic transitions of Er3+ ions. We observed the upconversion photoluminescence (UCPL) at 530, 550, 660 and 810 nm under 980 nm excitation. In the Ge25Ga9.5Sb0.5S65: 0.1 at.% Er3+, we found that the Stokes photoluminescence (PL) at the green spectral region excited by the 490 and 532 nm laser is only ≈5 times higher than the UCPL emission under 810 or 980 nm excitation making these materials attractive for UCPL applications. The addition of 0.1–1 at.% of Yb3+ into Ge25Ga9.5Sb0.5S65: 0.1 at.% Er3+ glass reduces the UCPL as well as the Er3+ ≈1.5 μm emission intensity probably due to the reabsorption processes of the excitation light and concentration quenching. However, the observed Er3+: 4 S 3/2→4 I 13/2 (≈850 nm) emission in the Ge25Ga9.5Sb0.5S65: 0.1 at.% Er3+ sample populates the 4 I 13/2 level, which promises the using of this material for the 1.5 μm optical amplification.

Doping of semiconductor quantum dots (QDs) by transition metals (such as Mn, Cu, Ni, etc.) is a great technique to impact the optical and structural properties of the host materials. The introduction of a small amount of impurity into the host semiconductor matrix leads to the shift of PL emission due to the change in the recombination process. The new emission pathways created by dopant influence the photoluminescence intensity, Stokes shift, lifetime and stability of QDs. Mn-doped ZnS QDs (1–15 mol. %) have been synthesized by the effective low-cost and nontoxic hot-injection method. N-phenylmorpholine-4-carbothioamide has been successfully applied as a novel source of sulfur in the synthesis of Mn-doped ZnS QDs. X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and infrared (IR) spectroscopy were used for the characterization of morphology and structure of synthesized Mn-doped ZnS QDs. Our materials exhibit strong photoluminescence yellow-orange emission with a photoluminescence quantum yield (PL QY) of 41%. All Mn-doped ZnS QDs have a face-centered cubic structure with a mean crystalline size of 3.8–5.1 nm. Additionally, this synthetic approach enables the synthesis of Mn-doped ZnS QDs with tunable band gaps between ∼3.5 eV and 3.60 eV.

Herein described the preparation of swelling pearl-like copolymer styrene—4-vinylbenzyl chloride cross-linked by means of tetra(ethylene glycol)-bis(4-vinylbenzyl)ether (200–800 μm). The pearl-like polymer was used to anchor (1 R ,2 R )-1-amino-2-(2,3-dihydro-1 H -isoindole-2-yl)-1,2-diphenylethane by a covalent bond; the product was subsequently transformed into the corresponding complex with Cu(II) acetate. The synthesized catalyst was used for the catalysis of the Henry reaction of functionalized aldehydes with nitromethane in ethanol. The reactions proceeded in a polymeric matrix of the swelling catalyst at a rate comparable with the rates of reactions in a homogeneous medium. The corresponding functionalized 2-nitroethanols were formed in quantitative yields (20 °C, 24 h) with enantiomeric excess values of up to 96%. The catalyst was recycled five times without losing its effectiveness with regard to the yield and enantioselectivity; only a partial mechanical degradation of the polymeric matrix occurred due to stirring.

We report on compositional tuning in Er3+ ions doped Ga–Ge–Sb–S glassy system allowing for effective 2H11/2→4I15/2 (530 nm), 4S3/2→4I15/2 (550 nm), 4F9/2→4I15/2 (660 nm), 4I9/2→4I15/2 (810 nm), 4I11/2→4I15/2 (990 nm) intra-4f electronic transition emissions of Er3+ ions under 808 nm, 980 nm or 1550 nm laser pumping. We changed the composition of well-known Ge20Ga5Sb10S65 glass to Ge25Ga10−xSbxS65, where x=0.5 at%, 2.5 at% or 5.0 at% and doped it with 0.5 at% of Er3+ ions. The short-wavelength absorption edge of the studied glassy hosts is blue-shifted by substitution of Sb with Ga to ~500 nm making the green emission at 530 nm and 550 nm and even 495 nm (4F7/2→4I15/2) observable, while the glass stability was kept high characterized with the difference of Tc−Tg>100 K and mean coordination numbers 2.67–2.71. Up-conversion emission decay times of all anti-Stokes emissions were in the range of 0.2–2.1 ms. The influence of Ga substitution with Sb on the structure and the optical properties was investigated. The spectroscopic parameters for Er3+ ions with local environment change were analyzed based on Judd–Ofelt theory.

The study examines the physico-chemical properties of thin films of the As–In–S:Sm system. Thin amorphous films were prepared by thermal evaporation (TE) from two sources (As–In–S glass and metallic Sm) and by pulsed laser deposition (PLD). The films prepared with PLD contained more Sm and In than the TE films. The optical gap of the PLD films is lower than that of the TE films (E g opt = 2.29 eV for TE, E g opt = 1.88 eV for PLD), both are dependent on exposure of films and on their annealing. The as-deposited PLD films did not contain any separated As 4 S 4 molecules; overstoichiometric arsenic was incorporated into the amorphous matrix. The index of refraction of the prepared PLD films (n ћ ω → 0 = 2.48) is higher than that of the TE films (n ћ ω → 0 = 2.35). The corresponding coefficient of the third order non-linear optical susceptibility (χ (3) ) is also higher (PLD: 6.83 × 10 − 20 m 2 /V 2 , TE: 4.02 × 10 − 20 m 2 /V 2 ). The structural changes induced by exposure and by annealing, determined by Raman spectroscopy, can be described through photochemical reactions (induced by exposure) and chemical reactions (induced by annealing). The strong luminescence bands were assigned to inner f–f electron transitions. The material is promising for a number of applications.

Homogeneous glasses of the system 80GeSe 2 ·(20− x )Sb 2 Se 3 · x Sb 2 Te y :0.03Pr 2 Se 3 glasses; x =0, 1, 3, 10; y =2, 3, 4 were prepared. The glasses with x =0–3 are very stable without any crystallization for T T g values (261–309 °C) and the E g opt values (1.30–1.70 eV) are decreasing with the Te content. The index of refraction is high (2.55–2.73 for 2200 nm), it is increasing with increasing Te content. The Raman spectra revealed presence of GeSe 4/2 tetrahedra, Ge 2 Se 6/2 bi-tetrahedra and SbSe 3/2 trigonal pyramids in studied glasses. The tellurium atoms are forming SbSe 2 Te and SbSeTe 2 distorted pyramids. The strong luminescence corresponding to 4f transitions in Pr 3+ ions was found in spectral regions (1100–1450 nm, 1500–1700 nm, 1750–2000, 2000–2600 nm and 3600–5200 nm; λ exc =980, 1050 and 1550 nm). The intensities of luminescence bands depend on their composition. The prepared glasses are promising candidates for infrared luminescence applications in NIR and MID IR region up to λ ≈5200 nm. High index of refraction and high value of third-order non-linear optical susceptibility χ (3) (≈300 times higher than χ (3) for SiO 2 ) are promising for application of these glasses in optoelectronic devices. Good glass forming parameters are perspective for preparation of fibers.

The electric properties of LiI containing chalcohalide glasses in the system Ga2S3–GeS2 were studied by means of impedance spectroscopy and potentiostatic chronoamperometry. Two sets of the samples were prepared by direct synthesis from elements and compounds in evacuated quartz ampoules. The prepared glasses were as follows: xLiI–xGa2S3–(100−2x)GeS2, x = 15, 20, 25 and 20LiI–xGa2S3–(80−x)GeS2, x = 0, 5, 10, 15 and 20. In the first set the concentration of LiI increased and the second set was prepared to study the influence of Ga2S3 on the properties of the glasses. Additional aim of this work was to compare the electric properties of LiI containing Ga2S3–GeS2 glasses with analogous AgI containing Ga2S3–GeS2 glasses recently studied by us. The conductivity of the LiI containing glasses in the Ga2S3–GeS2 system was higher and the activation energy was lower than in the analogous AgI containing system. The residual electronic (hole) conductivity remained similar in both systems being almost negligibly low. Raman spectroscopy proved the influence of LiI as well as Ga2S3 on glass structure, however interpretation of Raman spectra of these glasses is complicated due to small mass difference between gallium and germanium.

The infrared emission properties of rare-earth (i.e., Dy 3+ , Pr 3+ or Sm 3+ ) and nickel-codoped Ge–Ga–Sb–S glasses were investigated by photoluminescence measurements. It was found that the emission intensities of the rare-earth doped glasses were significantly weakened even with very few amount of nickel (i.e., 500 at. ppm). On the other hand, the nickel-doped glasses show larger indices of refraction, which property will be desirable in nonlinear optics. Our results, however, suggest that to obtain rare-earth doped chalcogenide glasses of better infrared emission property it is necessary to keep the nickel dopant as low as possible.

Glasses of systems 100-y((GeS 2 ) 80 (Sb 2 S 3 ) 20− x (PbI 2 ) x )yPr 2 S 3 , x = 0; 2; 5, 8; y = 0; 0.01; 0.1; 0.5 and 99.9-z((GeS 2 ) 80 (Sb 2 S 3 ) 18 (PbI 2 ) 2 )0.1Pr 2 S 3 zYb 2 S 3 , z = 0.05; 0.1; 0.15) were synthesized in high purity. Optically well transparent glasses were obtained for x ⩽ 5 mol.% PbI 2 , for y ⩽ 0.1 mol.% Pr 2 S 3 and for z ⩽ 0.15 mol.% Yb 2 S 3 . The glasses were stable and homogeneous, as confirmed by X-ray diffraction and electron microscopy, with high optical transmittivity from visible (red) region up to infrared region (∼900 cm −1 ). The density of the glasses was 3.26–3.33 gcm −3 for PbI 2 containing glasses. The glass transition temperature, T g , was ∼320–336 °C. The optical absorption bands in rare-earth doped glasses corresponded to 3 H 4 – 3 F 4 , 3 H 4 – 3 F 3 , 3 H 4 –( 3 F 2 + 3 H 6 ) f–f electron transitions of Pr 3+ ions and to 2 F 7/2 – 2 F 5/2 f–f electron transitions of Yb 3+ ions. Strong luminescence band with maximum near 1340 nm (electron transition 1 G 4 – 3 H 5 ) was found in Pr 2 S 3 doped glasses. The intensity of this band was rising with doping by Yb 3+ ions. The possible mechanism of the luminescence enhancement is suggested.

The optical and structural properties of Ge 20 Se 80 , Ge 25 Se 75 and Ge 30 Se 70 bulk glasses and Ag x (Ge 0.20 Se 0.80 ) 100− x thin films, where x = 0, 6, 11, 16, 20 and 23 at.% were studied. All samples were confirmed as amorphous according to XRD. The Raman spectra showed increase in 260 cm −1 and 237 cm −1 and decrease in 198 cm −1 and 216 cm −1 bands with different Se content in the bulk samples. The optical bandgap energy of bulk samples decreased (2.17–2.08 eV) and refractive index increased (2.389–2.426 at 1550 nm) with increasing Se content in bulk glasses. The Ge 20 Se 80 thin films were prepared by vacuum thermal evaporation from Ge 30 Se 70 bulk glasses. The Raman spectra of the films showed that peaks at 260 cm −1 and 216 cm −1 decreased their intensities with increasing Ag content in the thin films. The significant red shift of bandgap energy occurred upon different Ag content. The optically induced dissolution and diffusion resulted in graded refractive index profile along the film thickness caused by different Ag concentration. The refractive index increased from the substrate side to the top of thin films. The graded profile was getting more uniform with increasing content of silver in the thin film.

Thin amorphous films from system (As2Se3)80−x(As2Te3)x(SnTe)20 were prepared by pulsed laser deposition (PLD) from their bulk glasses and their optical properties were studied by spectral ellipsometry. Spectral dependencies of refractive index, absorption and extinction coefficient and optical gap (1.41–1.66 eV for (As2Se3)80−x(As2Te3)x(SnTe)20 with x = 20 resp. x = 0) were calculated from optical tansmittance, from ellipsometric data by Tauc method. High values of refractive index n0 (2.49–2.60) and of non-linear χ(3) coefficient of index of refraction (4.9–7.5 × 10−12 esu for the glass (As2Se3)80−x(As2Te3)x(SnTe)20 with x = 0 resp. x = 20) made studied thin films of system (As2Se3)80−x(As2Te3)x(SnTe)20 promising candidates for application in optics and optoelectronics.

International audience; Thermal, optical and electrical properties of the Agx(Ge28Sb12Se60)100x system (for x = 0 to 20) are systematically studied using various characterization techniques. In the present study, we have shown the reproducibility of the current results with the previously published literature and several novel results are also presented. The impedance data for the understanding of electrical properties of the materials has been analyzed using the random-walk (RW) model. We observed that, Ag playing two different concentration dependent roles i.e. above and below the 5% of Ag concentration, which is confirmed by the Raman analysis. The anomalous behaviors of electrical conductivity, optical and thermal properties with increasing Ag concentrations are explained by the role of Ag in the structural modification. We compared the diffusion coefficient (D), obtained from the RW model analysis with the experimental data(obtained from tracer diffusion) and found diffusion coefficient (D), obtained from the RW model are in good agreement corresponded with the experimental values. We also found a major change in conductivity of insulating Ge28Sb12Se60 (~ 10-14 S·cm-1) to a fast ionic conductor for Ag15(Ge28Sb12Se60)85 (~ 10-6 S·cm-1), i.e., a nine orders of magnitude. We demonstrated that the random-walk model can replacea time consuming and expensive tracer diffusion method for the determination of D. The present article helps to understand the ion conduction mechanism in disordered / amorphous materials.

The phase change memory materials (PCMM), their composition, structure, properties and crystallization are discussed. Formation of intermediary phases with high density of substitutional defects during high-speed crystallization of their amorphous forms is suggested.

Principles, advantages, applications and drawbacks of pulsed laser deposition (PLD) technique for thin films preparation are reviewed. The PLD method is promising for preparation of thin films of complex composition, including rare-earth and Ag-doped chalcogenide films; all components of the target can be evaporated at once. Low volatility and refractory materials can be also deposited. The deposition in vacuum, inert or reactive atmosphere is possible. Results obtained in a study of chalcogenide films are discussed and the current state-of-the-art is reviewed. The composition and structure of PLD films can be different from thermally evaporated films and new materials or materials with new properties applicable in optics and optoelectronics can be prepared. The method can be used for fabrication of different chalcogenide-based sensors and memory materials of complex composition. Photoinduced changes of structure and properties of PLD films and chalcogenides exposed to intense laser pulses are also discussed. The intense laser pulses can change the properties of the materials prepared and can be used for fabrication of chalcogenide-based waveguides, diffractive elements and high-density optical data storage media.

Pure and Sm 3+ doped amorphous thin films of Sb 2 S 3 were prepared by thermal co-evaporation of Sb 2 S 3 and Sm metal. The prepared films contained a slight over-stoichiometric excess of Sb. From transmittance measurement, the absorption edge, index of refraction, n , thickness, d , optical gap, E g opt , relative permittivity, e r , single oscillator energy, E o , dispersion energy, E d , and the values of third-order nonlinear susceptibility χ (3) were evaluated. The values of χ (3) increase with Sm doping. Some of above-mentioned values are slightly influenced by exposure of films to a UV lamp. The Raman spectra revealed two main structural units in the films: SbS 3 pyramids and Sb–Sb bonds in S 2 Sb–SbS 2 structural units. Three luminescence bands were found. The first one with maximum near 1130 nm can be assigned to 6 F 9/2 → 6 H 5/2 and/or 6 F 11/2 → 6 H 7/2 electron transitions, which are overlapping. The second band can be assigned to the electron transition 6 F 11/2 → 6 H 9/2 or 6 F 9/2 → 6 H 7/2 or 6 F 7/2 → 6 H 5/2 . The third luminescence band with maximum near 1500 nm can be probably assigned to the electron transition 6 F 11/2 → 6 H 11/2 .

The spectral dependence of third-order non-linear susceptibilities, χ (3) , of amorphous As–S thin films was evaluated from changes of index of refraction using Miller’s rule. The exposure of thin fresh evaporated films and their annealing increases χ (3) , it increases also their homogeneity and level of their polymerization as can be judged from Raman spectra of the films. The large covalently bonded parts (‘molecules’) of the samples are apparently favorable for increase of χ (3) .

The paper reviews and discusses crystalline, nanocrystalline, glassy and amorphous chalcogenides and their thin films and fibres, their preparation, structure, properties, changes and applications in optics, optoelectronics and electronics, data storage and sensors with accent on recent data and progress. The area of interest is so broad that only some materials and processes could be discussed in detail, and a lot of data were chosen for the sake of illustration only.

The title catalyst is employed for the reactions of functionalized aldehydes with nitromethane to give 2-nitroethanols in excellent yields and high enantioselectivities.

Homogeneous pure and dysprosium-doped (Ge30Ga5Se65)100−x(Dy2Se3)x glasses, x=0, 0.01, 0.05, 0.1, 0.2, 0.3, 0.5, were synthesized. From the room temperature absorption spectra, the experimental oscillator strengths of six f–f electron transitions of Dy3+ ions and Judd–Ofelt intensity parameters were evaluated. The Dy3+ induced absorption bands were assigned to electron transition from the ground level 6H15/2 to the 6H13/2, 6H11/2, 6H9/2, 6F11/2, 6F9/2, 6H7/2, 6F7/2 and 6F5/2 energy levels of Dy3+ ions. High values of the oscillator strengths and of the intensity parameter, Ω2, originate apparently from the high covalence of chemical bonds in studied glasses. Using the Judd–Ofelt theory, the spontaneous emission probabilities, the branching ratios and the emission cross-sections were calculated. In the emission spectra of (Ge30Ga5Se65)100−x(Dy2Se3)x glasses, seven infrared luminescence bands (1150, 1340, 1560, 1760, 2170, 2470 and 2950 nm) were observed when pumped by 808 nm light. Using 905 nm excitation light, five emission bands at 1150, 1340, 1760, 2470 and 2950 nm were found. Only three luminescence bands were identified (1760, 2470 and 2950 nm) when excited by 1300 nm light. The bands were assigned to the individual electron transitions. The long-wawelength absorption edge (∼700 cm−1) corresponds to multiphonon Ge–Se bonds vibrations.

The Ge25Ga5Se70 and Ge30Ga5Se65 pure and Pr3+-doped glasses were prepared by direct synthesis from elements and PrCl3. It was found that up to 1 mol% PrCl3 can be introduced in the Ge25Ga5Se70 and Ge30Ga5Se65 glasses. Both types of glasses with overstoichiometric and substoichiometric content of Se were homogeneous and of black color. The optical energy gap is E opt g =2.10 eV , and the glass transition temperature is T g =543 K for Ge25Ga5Se70 and T g =633 K for Ge30Ga5Se65. The long-wavelength absorption edge is near 14 μm and it corresponds to multiphonon processes. Doping by Pr3+ ions creates absorption bands in transmission spectra, which can be assigned to the electron transitions from the ground 3H4 level to the higher energy levels of Pr3+ ions 3H5, 3H6, 3F2, 3F3 and 3F4, respectively. By excitation with YAG:Nd laser line (1064 nm), two intense luminescence bands (1343 and 1601 nm) were excited. The first band can be ascribed to electron transitions between 1G4 and 3H5 energy levels of Pr3+ ions. Full width at half of maximum (FWHM) of the intensity of luminescence was found to be ∼70 nm for (Ge25Ga5Se70)1 − x(PrCl3)x and (Ge30Ga5Se65)1 − x(PrCl3)x glasses. The FWHM in selenide glasses is lower than in halide and sulphide glasses. The second luminescence band (1601 nm) can be probably ascribed to the transitions between 3F3 and 3H4 energy levels of Pr3+ ions. The absorption and luminescence spectra of Pr3+ ions in studied glasses are slightly influenced by stoichiometry of glassy matrix. The Raman spectra of studied glasses were deconvoluted and assignment of Raman bands to individual vibration modes of basic structural units was suggested. The structure of studied glasses is mainly formed by corner-sharing and edge-sharing GeSe4 tetrahedra. The vibration modes of Ga-containing structural units were not found, they are apparently overlapping with Ge-containing structural units due to small difference between atomic weights of Ge and Ga. In the glasses with substoichiometry of Se, the Ge–Ge bonds of Ge2Se6 structural units were found. In Se-rich glasses the Se–Se vibration modes were found. In all studied glasses also `wrong' bonds between like atoms were found in small amounts. Maximum phonon energy of studied glasses is ∼320 cm−1.

The (GeS 2 ) 80− x (Sb 2 S 3 ) 20 · x PrCl 3 and (GeS 2 ) 60− x (Sb 2 S 3 ) 40 · x PrCl 3 , ( x =0.01, 0.1, 0.5) glass systems were prepared from elements and PrCl 3 by thermal synthesis. The glasses were of orange to red colour, they were optically homogeneous up to 0.5 mol% of PrCl 3 , the samples with 1 mol% of PrCl 3 were partly crystalline. The homogeneity was confirmed by optical methods and by electron microscopy. The glass transition temperatures, T g , were between 330°C and 333°C for (GeS 2 ) 80− x (Sb 2 S 3 ) 20 · x PrCl 3 glasses and between 256°C and 274°C for (GeS 2 ) 60− x (Sb 2 S 3 ) 40− x · x PrCl 3 glasses, ( x =0.01, 0.1, 0.5). The short-wavelength absorption edge was between 550 and 700 nm for (GeS 2 ) 60− x (Sb 2 S 3 ) 40 · x PrCl 3 glasses and between 500 and 650 nm for (GeS 2 ) 80− x (Sb 2 S 3 ) 20 · x PrCl 3 glasses. The long-wavelength absorption edge was between 900 and 1000 cm −1 and is apparently caused by multiphonon absorption of Ge–S and Sb–S vibration modes. Doping with Pr 3+ ions creates new absorption bands near 2100, 4980, 6370, 6640 and 9843 cm −1 , which are assigned to the electron transitions from the 3 H 4 level of Pr 3+ to the 3 H 5 , 3 H 6 , 3 F 2 , 3 F 3 , 3 F 4 , 1 G 4 levels, respectively, of the Pr 3+ ion. The absorption bands corresponding to 3 H 4 → 3 H 6 , 3 F 2 and to 3 H 4 → 3 F 3 , 3 F 4 transitions are overlapped. The Raman spectra were deconvoluted into several bands, which can be assigned as the vibrations of GeS 4 , SbS 3 and S 8 structural units. The structure of these glasses can be described as interconnected GeS 4 tetrahedra and SbS 3 pyramids with dissolved S 8 molecules and Pr 3+ ions. The luminescence spectrum consisted of two luminescence bands. The one at ∼1300 nm, was assigned to 1 G 4 – 3 H 5 electron transitions of the Pr 3+ ions. The other luminescence band of smaller amplitude was ∼1600 nm and assigned to transitions between the 3 F 3 and 3 H 4 electron levels of Pr 3+ .

The irreversible and reversible photoinduced changes of the structure and physical properties of stoichometric and non-stoichiometric As x s 100− x ( x = 38, 40 ) thin films were studied. The changes in intensities of Raman bands were interpreted in terms of changes of shortrange order. The illumination and/or annealing of fresh-evaporated As S system thin films change the as 4 s 4 and S n , contents as well as the densities of As As and S S bonds. Illumination and annealing shift the short wavelength absorption edge towards lower energies and changes the index of refraction. The energy dependence of the index of refraction, n , can be described by the Wemple-DiDomenico dispersion relationship n 2 (ħω) − 1 = E o E d /[ E o 2 − (ħω) 2 ], from which the single oscillator energy, E o and the dispersion energy, E d , were determined. The dependence of E o , E d , n , and of the thickness of the sample d on the stoichiometry, illumination and annealing are also discussed.

High purity (GeS2)8−x (Sb2S3)20(NdCl3)x x=0, 0.01, 0.1, 0.5, glasses were prepared and their optical properties determined. The Ge-Sb-S system dissolves up to 0.5 mol.% of NdCl3 and still forms stable glasses. The structure of these glasses is formed by interconnected GeS4 tetrahedra and SbS3 pyramids as it follows from the Raman spectra. The glasses are optically well transparent in the range from 15400 cm−1 to 1000 cm−1. Doping with Nd creates new absorption bands which can be assigned to electron transfer from the 4 I 9/2 level to 2 G 5/2, 2 G 7/2, 2 H 11/2, 4 F 9/2, 4 F 7/2, 4 S 3/2, 2 H 9/2, 4 F 5/2, 4 F 3/2, 4 I 13/2 and 4 I 11/2 levels. The oscillator strengths and Judd-Ofelt parameters were evaluated. Their values are close to the values of those for Nd3+1 in another chalcogenide hosts. The long-wavelength absorption edge was found near 1000 cm−1 and is due to multiphonon Ge-S and Sb-S vibrations. In doped glasses, several broad luminescence bands near 890, 1080, 1370, and 1540 nm were found. They can be attributed to the transitions from 4 F 3/2 to 4 I 9/2, to 4 I 11/2, to 4 I 13/2 and 4 I 15/2 electron levels. The first luminescence band was excited also by 1064-nm line and represents probably the upconversion of light.

High purity (GeS2)80−x(Ga2S3)20·xNdCl3 (x=1, 2, 3) and (GeS2)79(Ga2S3)20·Nd2O3 glasses were prepared and their thermal and optical properties measured. The GeS2–Ga2S3 glasses can dissolve relatively large amounts of NdCl3 and Nd2O3 (≤3 mol%) and still form stable glasses. They are optically transparent in the range from 19000 cm−1 to 800 cm−1. The glass transition temperature (Tg≅378°C) and the glass-forming criteria are only slightly changed by Nd doping (ΔT=147°C, Hr=0.78; H′=0.39, S=4.10 K, where ΔT=Tc−Tg, Hr is Hruby's criterion, Hr=(Tc−Tg)/(Tm−Tc), H′=(Tc−Tg)/Tg, and S=(Tc−Tx)(Tc−Tg)/Tg). The short-wavelength absorption edge lies near 2.7 eV, doping with Nd creates new absorption bands which can be assigned to electron transfer from the 4 I 9/2 level to 4 G 7/2, 4 G 9/2, 2 K 13/2, 2 G 5/2, 2 G 7/2, 2 H 11/2, 4 F 9/2, 4 F 7/2, 4 S 3/2, 2 H 9/2, 4 F 5/2, 4 F 3/2, 4 I 15/2, 4 I 13/2 and 4 I 11/2 levels. In doped glasses, several broad luminescence bands, near 910, 1080 and 1360 nm, were found, which can be assigned to the transitions from 4 F 3/2 to 4 I 9/2, to 4 I 11/2 and to 4 I 13/2 electron levels. The long-wavelength absorption edge was found near 1000 cm−1 and is due to multiphonon Ge–S and Ga–S vibrations.

High purity (GeS2)80−x(Ga2S3)20·xPrCl3 (x= 1,2,3), (GeS2)79(Ga2S3)20Pr6O11 glasses were prepared and their basic thermal and optical properties were detemuned. The glass transition temperature Tg is in the region 399–404°C. The glass-forming criteria (ΔT ∈ (123–128°C), Hr ∈ (0.59–0.66), S ∈ (2.37–3.29) are changed by Pr doping only a little. The short-wavelength absorption edge lies near 2.7 eV, the doping by Pr creates new absorption bands which can be assigned to the 3H4-3H6, 3H4-3F3, 3H4-3F4, 3H4-3P0 and 3H4-3P1 electron transitions. The experimentally found oscillator strengths calculated from absorption spectra lies between those of Pr doped halide and chalcohalide glasses. The long-wavelength absorption edge was found near 800–1000 cm−1 and it corresponds to multiphonon Ge-S and Ga-S vibrations. The far-IR diffuse reflectance spectra were measured and the spectrum revealed by Kubelka-Munk method. The spectrum was deconvoluted into several bands which can be assigned to GeS4 and GaS4 tetrahedra vibrations. The narrow luminescence bands corresponding to electron transitions in Pr3+ ions (20000, 17857, 15873, 15220, 14326, 13947 and 13459 cm−1) with the most intensive band near 15220 cm−1 were found. These bands can be assigned to the transitions from the 3P0 and 1D2 levels to 3F4, 3F3, 3F2, 3H6, 3H5 and 3H4 levels. The most intensive band corresponds to the 3P0-3F2 transitions.

Er3+-doped Ge25Ga5Sb5S65 chalcogenide glass was studied as a potential material for up-conversion application to enhancement of silicon solar cell efficiency. Thermal properties were studied via DSC measurement, optical properties via variable angle spectroscopic ellipsometry and photoluminescence measurement. The host chalcogenide glass shows good thermal, chemical and physical properties. The band gap energy is ~2.23 eV which allows to emit green and red luminescent light from 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 4f-4f transitions of Er3+ ions under 800 nm pumping with Ti-sapphire tunable laser.

New glasses of composition 30 CdCl 2 - 50 PbCl 2 - 30 KI doped with 0.1; 0.5; 3; 5; 10; 15; 25 or 30 mol% PbO were prepared and their thermal (T g , T x , T c , T m ), and optical (T, R, diffuse reflectivity) properties from the visible to the far IR region were determined. The glass-forming ability is enhanced by doping with lead oxide and glasses of thickness up to 1 cm can be prepared. The glass transition temperature T g of investigated glasses is in the 84–120°C range, the temperature of crystallization T c is in the 122–146°C domain. The glasses are transparent from 22000 cm −1 up to 1000 cm −1 . The origin of IR absorption bands near 3450, 900 and 365 cm −1 is discussed.

International audience; Electronic transitions of Pr3+ ions in Ga-Ge-Sb-Se glasses corresponding to emissions in the infrared region were studied by means of absorption and emission spectroscopies and fluorescence lifetimes measurements. Transition probabilities, radiative lifetimes, branching ratios, and quantum efficiencies of most of the emission transitions including the infrared ones occurring around 1.3, 1.7, and 2.4 μm were estimated based on a standard Judd-Ofelt analysis.

The exposure of amorphous and glassy materials, including many chalcogenides and some chalcogens, changes their structure, surface and physicochemical properties. The changes of optical transmittivity, reflectivity and index of refraction can be applied for construction of optical memories, holographic recordings, lenses, microlenses etc. The changes of reactivity can be applied for fabrication of photoresists of very high resolution, for fabrication of optical gratings and optoelectronic devices transparent in the infrared region etc.

New results of the study of photoinduced effects in amorphous chalcogenide layers and glasses are reviewed. The main accent is given to the changes of short range order, to the mechanisms of optically induced effects, to the optically induced changes of reactivity of chalcogenide layers. Both irreversible and reversible effects are discussed. Attention is paid also to different materials in which the photoinduced effects were studied recently.

The intense 1.32, 1.73, and 2.67 μm near-infrared and midinfrared emissions were observed from the Dy3+-doped GeSe2–Ga2Se3–MI (M=K, Cs, Ag) chalcohalide glasses. These glasses are red light transparent therefore can be pumped by a semiconductor lasers operating at ∼808 nm. The 2.67 μm emission has not been reported yet which corresponds to an absorption minimum in fluoride fibers and can be very useful for long distance communications. The intensity of emissions is very sensitive to the local chemical environment of Dy3+ ions embedded in these metal halide modified glasses. A plausible correspondence between the emission intensity and the average oscillator strength was found.

When irradiated by the focused Ar+ ion laser of below band-gap photon energy (2.41 and 2.54eV), a large increase of refractive index (e.g., Δn=6% at 1550nm) was observed in 60GeS2–20Ga2S3–20AgI bulk glass (with bandgap of 2.71eV). We found it surprisingly that such a large Δn quickly smeared out after the illumination even at room temperature, i.e., the refractive index will return to almost initial value within only 2h. It is fairly rare among chalcogenides ever reported. The plausible correlation between the photorefraction effect and the ion-conducting property of glasses was also suggested.

We report the kinetics of below band-gap light induced photodarkening in (80-x)GeS(2)-20Ga(2)S(3)-xAgI (x = 0 and 20 mol %) bulk chalcogenide glasses by measuring the time evolution of transmission spectra at every 10 milliseconds. The results prove clearly the enhancement of photosensivity upon doping of AgI compound in glasses. It is interesting to find that PD observed in AgI-doped glass totally disappears two hours later after the laser exposing even at room temperature. In significant contrast to 80GeS(2)-20Ga(2)S(3) glass that the metastable part of PD remains for a long time. We expect such a fast auto-recovery property in AgI-doped glass can be utilized for optical signal processing.

The intensity of two electron paramagnetic resonance signals with effective g -values of 2.0 and 4.3 was measured in the temperature region 4–40 K in Mn 2+ -doped halide glasses of the type CdCl 2 PbCl 2 KI and in chalcohalide glasses of the type GeS 2 Ga 2 S 3 MnCl 2 . The experimental ratio of the intensities of the two resonances in glasses with an Mn 2+ ion content lower than 1.0 mol% MnCl 2 was fitted to the ratio of the two Boltzmann distribution functions calculated with the spin-Hamiltonian parameters of the two magnetically active centers. Some type of exchange interaction was assumed to be present in the other glasses. This interpretation agrees with the experimental evidence of changes of the shape of the resonance signal as well as with the simulation of the intensity ratio curves.