Academic literature on the topic 'Sintesi colloidale'

ABSTRACTSimple synthesis of nanospherical TiO2 by microwave hydrothermal method has beeninvestigated. Titanium tetra isopropoxide (TTIP) and tetra methyl ammonium hydroxide(TMAOH) were used as precursor. The crystal phase and microstructure were characterized byX-Ray Diffraction (XRD) and transmission electron microscopy (TEM) including selected areadiffraction (SAED). The presence of intense peak in the XRD patterns confirmed to anatase andin good agreement with SAED patterns. Nanospherical of particles were clearly seen in theTEM image and the size of particles was approximately 4-5 nm.Keywords : microwave hydrothermal, colloidal titanates, structure directing agent,nanospherical TiO2

Nowadays silver nanoparticles (AgNPs) synthesized so often by plant extracts as a reductor. The synthesis of AgNPs was carried out by Citrus microcarpa Bunge fruit peel extract a reductor in various extract concentrations (10, 15, and 20%), concentration of AgNO3 solution of 0.15M and temperature of 700C. The presence of AgNPs was determined by color test and the formation of Surface Plasmon Resonance (SPR) using UV-Vis Spectrophotometer while to determine the morphology and size of the nanoparticles using Scanning Electron Microscope (SEM). The results of the analysis showed that AgNPs was formed at colloidal phase with dark brown color with wavelengths of 457.30 nm, 478.90 nm, and 422.80 nm for variation concentration of 10, 15 and 20% with slightly spherical, slightly elongated and jagged morphology with average size of 253.8 nm (10%), 254.2 nm (15%) and 253.9 nm (20%).

<p><em>Drilling is one of the important things in the drilling process, from the start of drilling to the point of reaching the intended depth, can assist the smooth process of drilling. The potential problems that can arise one of them is the drilling mud reply (loss of circulation). One way to prevent and cope with the discovery of drilling mud is dissolved. At this time Polymers Synthesis and Sago Flour as material for dissolved system. Both materials enter into the colloidal effect. The colloid solution itself is a relatively large, relatively large dispersion system within the dispersing medium.</em></p><p><em>The purpose and objective in collecting these tasks is to determine the effectiveness of Synthetic and Sago Flour Polymer materials in tackling the drilling mud stock problem. Based on the results of the research found, that A sludge system can provide most of the standard specification where the value of physical properties and rheology. While the B sludge system is inversely proportional, most of it does not meet the standard specification. It can be underlined that B system with Sago Flour as LCM is effective in handling dispersion drilling mud.</em></p>

Konsumsi minyak bumi mengalami peningkatan dari tahun ke tahun, sementara produksinya cenderung mengalami penurunan. Produksi minyak bumi dapat ditingkatkan dengan oil recovery. Sejak tahun 1980, teknik Enhanced Oil Recovery (EOR) dengan menggunakan surfaktan sebagai penginjeksi (surfactant flooding) merupakan salah satu teknik yang paling berhasil untuk meningkatkan produksi minyak. Surfaktan dapat dibuat dari bahan alami, salah satunya dari minyak jarak pagar. Tujuan dari percobaan ini adalah untuk mengkaji pengaruh waktu reaksi dan pengaruh penambahan metanol terhadap metil ester sulfonat (MES, surfaktan) yang dihasilkan dalam operasi sulfonasi. Surfaktan yang diperoleh kemudian diaplikasikan dalam proses EOR. Proses pembuatan MES dari minyak biji jarak dilakukan melalui 2 tahapan yaitu proses esterfikasi dan transesterifikasi dengan katalis batu dolomite. Metil ester (ME) yang diperoleh kemudian disulfonasi untuk mendapatkan MES. Konsentrasi surfaktan anionik dalam produk dianalisa dengan spektrofotometer. Hasil penelitian menunjukkan bahwa MES yang memiliki kandungan surfaktan anionik paling tinggi diperoleh pada waktu reaksi 90 menit dan penambahan metanol dengan konsentrasi 40%wt yaitu sebesar 55,464 mg/L. Uji kompatibilitas didapatkan larutan berwarna keruh (koloid), sedangkan tegangan antarmukanya sebesar 17,71 dyne/cm dan tegangan antarmuka pada suhu 80oC adalah 26,57 dyne/cm. Petroleum consumption has increased from year to year, while production tends to decline. Petroleum production can be increased by oil recovery. Since 1980, the Enhanced Oil Recovery (EOR) technique using surfactants as injectors (surfactant flooding) is one of the most successful techniques for increasing oil production. Surfactants can be made from natural ingredients, one of them from jatropha oil. The purpose of this experiment was to examine the effect of reaction time and the effect of adding methanol to methyl ester sulfonate (MES, surfactant) produced in sulfonation operations. The surfactants obtained are then applied in the EOR process. The process of MES production from castor oil is carried out through 2 stages, namely esterfication and transesterification with dolomite catalyst. Methyl esters (ME) were obtained then sulfonated to obtain MES. The concentration of anionic surfactants in the product was analyzed by a spectrophotometer. The results showed that the MES which had the highest anionic surfactant content was obtained at the reaction time of 90 minutes and the addition of methanol with a concentration of 40% wt was 55.464 mg/L. Compatibility test obtained colloidal colored solution (colloid), while surface tension was 17.71 dyne/cm and surface tension at 80oC was 26.57 dyne/cm.

AbstractOpaline silica residue accumulates on the surface and in the near surface of the Te Kopia, Tikitere and Rotokawa geothermal fields, where rhyolitic tuffs are attacked by steam condensate, made acid (pH 2–3) by sulphuric acid produced by oxidation of H2S that accompanies steam discharge. Silica residue is one product of this alteration process that also yields kaolinite, sulphur, sulphide and aluminous sulphates, including alunite and alunogen, as pH, Eh and available moisture fluctuate across the field surface. Coagulation of colloidal polymeric silica or, possibly, direct deposition of monomeric silica can occur from the acid solutions of the digested country rock, depending on pH, concentration, temperature and the presence and concentration of other species. As with silica sinter, the first-formed silica phase consists of disordered opal-A microspheroids, commonly 0.1–5 μm in diameter. These coalesce and become overgrown by further opaline silica to yield a mass resembling gelatinous ‘frog spawn’ that lines cavities and envelops surfaces. This mass is the principle component of botryoidal, transparent to translucent hyalite that comprises much residue. Following deposition, this juvenile residue may crystallize to opal-CT lepispheres, 1–3 μm across and, subsequently, to chalcedonic quartz. Both the opal-A and opal-CT of the New Zealand residues are more disordered than those occurring in typical moderate- to low-temperature sinters. The opaline silica of silica residues enjoys a reaction relationship with both kaolinite and aluminium sulphates, including alunite and alunogen. These phases and the silica precipitate continuously and undergo dissolution at the surface of all three localities. The precise pathway followed depends upon the prevailing surface conditions, including humidity, pH, Eh, and Al and K activities. As Al is flushed from the system, the ultimate stage of alteration that may result is the dissolution of the silica itself in acidified rainwater, fogdrip or further steam condensate.

Le nanoparticelle (NP) di SiO2 sono note per migliorare le proprietà meccaniche e funzionali dei materiali nanocompositi (NC) e sono ampiamente utilizzate come filler di rinforzo negli pneumatici. Le proprietà dei NC dipendono dalla distribuzione delle NP di filler, che a sua volta dipende dalla morfologia e dalla chimica superficiale delle NP. La dispersione di SiO2 NPs idrofiliche in matrici polimeriche è tipicamente ottenuta tramite funzionalizzazione con silani a catena corta. Mentre le NP anisotropiche sono note per auto-organizzarsi in strutture ordinate, producendo migliori proprietà meccaniche nei NC elastomerici, è stato dimostrato che anche le NP sferiche di SiO2 ricoperte con catene di oligomeri, ovvero le SiO2 Hairy NP (SiO2 HNP), possono migliorare la compatibilizzazione filler/matrice mentre si auto-organizzano in superstrutture anisotropiche. Tuttavia, la sintesi di SiO2 HNP con gusci elastomerici è ancora largamente inesplorata, e la relazione tra l'auto-organizzazione delle HNP e le proprietà meccaniche dei NC deve ancora essere del tutto compresa. In questo contesto, lo scopo di questa tesi è stato quello di i) sviluppare una sintesi efficiente di SiO2 HNPs con dimensioni, morfologia e chimica di superficie controllate; ii) preparare NC elastomerici basati su SiO2 HNP con rinforzo migliorato e isteresi ridotta; iii) valutare gli effetti dell'auto-organizzazione sulle prestazioni meccaniche dei materiali e iv) studiare le interazioni tra SiO2 HNPs per determinare quali parametri controllano i processi di auto-organizzazione. Durante il primo anno di attività di dottorato è stata ottimizzata la sintesi di SiO2 HNP funzionalizzate con polibutadiene (PB) con un approccio colloidale. La sintesi ha garantito un eccellente controllo della morfologia e della chimica di superficie delle HNPs. Le particelle non funzionalizzate e funzionalizzate sono state completamente caratterizzate con una pletora di metodi morfologici e fisico-chimici mostrando evidenza di auto-organizzazione. Durante il secondo anno, le SiO2 HNP sono state utilizzate per preparare NC elastomerici in una formulazione industriale. Le proprietà meccaniche dei NC vulcanizzati e non vulcanizzati sono state caratterizzate da analisi dinamico-meccaniche e prove di trazione, mostrando che le HNP migliorano fortemente il rinforzo riducendo la dissipazione di energia, evidenziando migliori interazioni filler/matrice rispetto alle NP SiO2 non funzionalizzate e funzionalizzate con silano. La caratterizzazione morfologica delle NC ha confermato il miglioramento della dispersione e della distribuzione del filler con l'aumento della funzionalizzazione con PB e ha mostrato l'auto-organizzazione delle HNP in sovrastrutture anisotropiche simili a stringhe. Durante il terzo anno, il modello delle HNP è stato adattato a una formulazione riproducibile su scala industriale usando un silano macromolecolare a base di PB (MacroSil) e silice commerciale. Le proprietà meccaniche degli NC elastomerici sono state caratterizzate in modo approfondito con analisi meccaniche dinamiche, prove di trazione e analisi Large Amplitude Oscillatory Shear (LAOS), dimostrando che l'aggiunta di MacroSil migliora significativamente le prestazioni meccaniche degli NC rispetto a un silano a catena corta. Infine, esperimenti di Small-Angle X-Ray Scattering (SAXS) sulle dispersioni di SiO2 HNPs in collaborazione con il Prof. Simone Mascotto dell'Università di Amburgo hanno fornito parametri strutturali fondamentali che sono stati utilizzati per formulare un modello teorico delle interazioni tra HNP, in collaborazione con il Prof. Arturo Moncho dell'Università di Granada e il Prof. Gerardo Odriozola della UAM-Azcapotzalco. Il modello teorico ha predetto la formazione delle sovrastrutture anisotropiche di SiO2 HNP osservate sia nelle particelle prive di matrice sia nei NC elastomerici.
SiO2 nanoparticles (NPs) are known to improve the mechanical and functional properties of nanocomposite (NC) materials and are widely used as reinforcing fillers in tyres. The properties of NCs depend on the distribution of filler NPs, which in turn depends on the morphology and surface chemistry of filler NPs. The dispersion of hydrophilic SiO2 NPs in polymer matrices is typically achieved by functionalization with short-chain silanes. While anisotropic NPs are known to self-organize in ordered structures, producing improved mechanical properties in rubber NCs, evidence has shown that also spherical SiO2 NPs grafted with oligomer chains, i.e. SiO2 Hairy NPs (SiO2 HNPs), can improve filler/matrix compatibilization while self-organizing in anisotropic superstructures. However, the synthesis of SiO2 HNPs with rubbery shells is still largely unexplored, and the relationship between HNPs self-assembly and the mechanical properties of NCs is yet to be understood. In this context, the aim of this thesis was i) to develp an efficient synthesis of SiO2 HNPs with tunable size, controlled morphology and tailored surface chemistry; ii) to prepare rubber NCs based on SiO2 HNPs with improved reinforcement and reduced hysteresis; iii) to assess the self-assembly effects on the mechanical performance of the materials and iv) to study the interactions between SiO2 HNPs in order to determine which parameters control the self-assembly processes. During the first year of PhD activity the synthesis of polybutadiene (PB)-grafted SiO2 HNPs by a colloidal approach was optimized. The synthesis granted excellent control of HNPs morphology and surface chemistry. The bare and functionalized particles were fully characterized by a plethora of morphological and physico-chemical methods showing evidence of self-assembly. During the second year, SiO2 HNPs were used to prepare rubber NCs in an industrial formulation. The mechanical properties of the cured and uncured NCs were characterized by dynamic-mechanical analysis and tensile tests, showing that HNPs strongly improve reinforcement while reducing energy dissipation, highlighting improved filler/matrix interactions compared to both bare and silane-functionalized SiO2 NPs. Morphological characterization of the NCs confirmed the improvement of filler dispersion and distribution with increased PB functionalization and showed the self-organization of HNPs in anisotropic string-like superstructures. During the third year, the HNPs model was adapted to a scalable industrial rubber formulation using a PB macromolecular silane (MacroSil) and commercial precipitated silica. The mechanical properties of the rubber NCs were thoroughly characterized with dynamic mechanical analysis, tensile tests and Large Amplitude Oscillatory Shear (LAOS) analysis, showing that the addition of MacroSil significantly improves the mechanical performance of NCs compared to a short-chain silane. Finally, Small-Angle X-Ray Scattering of SiO2 HNPs dispersions in collaboration with Prof. Simone Mascotto at Hamburg University provided crucial structural parameters which were used to formulate a theoretical model of HNPs interactions, in collaboration with Prof. Arturo Moncho of the University of Granada and Prof. Gerardo Odriozola of UAM-Azcapotzalco. The theoretical model predicted the formation of the SiO2 HNPs anisotropic superstructures observed both in matrix free conditions and rubber NCs.

I concentratori solari luminescenti (LSCs) sono delle guide d’onda composti da una matrice polimerica drogata o ricoperta con fluorofori. La luce solare diretta e/o diffusa che penetra nella matrice è assorbita dai fluorofori e poi riemessa dagli stessi con energia minore. La luce emessa, grazie alla riflessione totale interna, propaga fino a raggiungere i bordi della guida d’onda dove è convertita in elettricità da celle fotovoltaiche poste sul perimetro della matrice. L’efficienza del dispositivo è ridotta da numerosi processi di perdita, sia dovuti alla riflessione della matrice e al cono di fuga, sia quelli che dipendono dalle caratteristiche dei fluorofori, come il coefficiente di assorbimento, il quantum yield (QY) di fotoluminescenza (PL) e il riassorbimento. Per minimizzare tali perdite, una buona alternativa ai tradizionali fluorofori sono i quantum dots (QDs) colloidali che presentano solitamente un elevato QY, un alto coefficiente di assorbimento e una lunghezza d’onda di emissione controllabile cambiando le dimensioni dei nanocristalli tramite modifiche dei parametri di sintesi. Inoltre, ingegnerizzando opportunamente i QDs, è possibile realizzare particelle con elevato Stokes-shift tra gli spettri di assorbimento ed emissione, in modo da ridurre quanto più possibile il riassorbimento. Il progetto si è quindi focalizzato sullo sviluppo della sintesi di QDs, al fine di ottimizzare il QY di fotoluminescenza, la compatibilizzazione con la matrice polimerica e la fotostabilità, limitando comunque il riassorbimento. Inoltre. la procedura di sintesi deve essere facilmente trasportabile su volumi industriali, per soddisfare il fabbisogno di produzioni di elevati metri quadrati di LSCs. Durante i tre anni di progetto di dottorato in Alto Apprendistato ho potuto sviluppare una procedura di sintesi che consiste in quattro step: • crescita di nanocristalli di CuInS2 core; • formazione del quaternario tramite aggiunta di zinco (ZnCuInS2); passaggio cruciale per aumentare il QY e controllare la lunghezza d’onda di emissione; • crescita di una shell di solfuro di zinco (ZnCuINS2/ZnS) per passivare la superficie dei nanocristalli, aumentare il QY e la fotostabilità; • trattamento post sintesi di scambio di leganti parziale per migliorare la solubilità nella matrice polimerica. I nanocristalli così prodotti mostrano un QY del 60% ed un’ottima solubilità nella matrice polimerica. Infatti, è stato prodotto un LSC di grande dimensione (30 cm x 30 cm x 0.7 cm) la cui optical power efficiency, OPE = 6.8%. Inizialmente ho sviluppato la procedura di sintesi in un pallone di vetro da 25 mL, producendo 250 mg a sintesi. Grazie all’attrezzatura fornita da Glass to Power S.p.A ho potuto studiare lo scale-up della sintesi. Dapprima ho effettuato studi preliminare, per approfondire alcune possibili problematiche dovute all’aumento dei volumi, su palloni di maggiori dimensioni, 500 mL e 2 L. Analizzate e risolte le tematiche di riscaldamento e stop della sintesi ho effettuato sintesi in un reattore preindustriale producendo 300 g di nanocristalli di ZnCuINS2/ZnS. Oltre ad incrementare la produzione di sintesi da 250 mg a 300 g mi sono occupata dell’ottimizzazione della procedura di sintesi. Ho testato diverse strategie per incrementare il QY senza danneggiare la solubilità nel polimero. Grazie ad una variazione di reagente nel secondo step e ad un incremento dei layer della shell ho ottenuto nanocristalli con 80% di QY. Il prossimo step sarà effettuare lo scale-up di questa nuova procedura e produrre LSC di grandi dimensioni. Grazie alle collaborazioni con altri studenti di dottorato ho sintetizzato nanocristalli di calcogenuro drogati oro e opportunamente decorati con molecole coniugate per sistemi di up-conversion. Grazie all’introduzione dell’oro in questi sistemi si è ottenuta un’efficienza di up-conversion del 12%.
Luminescent solar concentrators (LSCs) are waveguides composed of a polymeric matrix doped or coated with fluorophores. The direct and/or diffuse sunlight that penetrates the matrix is absorbed by the fluorophores and then re-emitted by them with less energy. The light emitted, thanks to the total internal reflection, propagates until it reaches the edges of the wave guide where it is converted into electricity by photovoltaic cells placed on the perimeter of the matrix. The efficiency of the device is reduced by numerous loss processes, due to the reflection of the matrix and the escape cone, and/or due to the characteristics of the fluorophores, such as the absorption coefficient, the quantum yield (QY) of photoluminescence (PL) and the reabsorption. To minimize losses due to fluorophores, a good alternative are colloidal quantum dots (QDs) that usually have a high QY, a high absorption coefficient and a controllable emission wavelength by changing the size of the nanocrystals. Furthermore, by properly engineering the QDs, it is possible to realize particles with high Stokes-shift between the absorption and emission spectra, in order to reduce the reabsorption as much as possible. The project is focused on the development of the synthesis of QDs, in order to optimize the QY of photoluminescence, compatibility with the polymer matrix and photostability, while limiting the reabsorption. Besides. the synthesis procedure must be easily transferable on industrial volumes, to meet the production needs of high square meters of LSCs. During the three years of the doctoral project in High Apprenticeship I was able to develop a synthesis procedure consisting of four steps: • growth of CuInS2 core nanocrystals; • quaternary formation with zinc addition (ZnCuInS2); crucial step to increase the QY and control the emission wavelength; • growth of a zinc sulphide shell (ZnCuInS2/ZnS) to passivate the surface of nanocrystals, increase QY and photostability; • post-synthesis treatment of the partial exchange of ligands to improve solubility in the polymer matrix. The nanocrystals thus produced show 60% QY and excellent solubility in the polymer matrix. In fact, a large size LSC (30 cm x 30 cm x 0.7 cm) was produced, whose optical power efficiency, OPE = 6.8%. Initially, I developed the synthesis procedure in a 25 ml glass flask, producing 250 mg for batch. Thanks to the equipment provided by Glass to Power s.p.A I was able to study the increase in the scale of the synthesis. Firstly, in order to investigate some possible problems due to the increase in volumes, I have carried out preliminary studies on larger balloons, 500 mL and 2 L. After analysis of heating and quenching of synthesis, I have performed the synthesis in a preindustrial reactor producing 300 g of nanocrystals of ZnCuInS2/ZnS. In addition I also optimized the synthesis procedure. I tested several strategies to increase QY without damaging solubility in the polymer. Thanks to a variation of the reagent in the second step and an increase of the shell layers, I obtained nanocrystals with 80% of QY. The next step will be to scale up this new procedure and produce large LSCs. I collaborated with other PhD students, in particular, I synthesized with a heat-up method CdSe nanocrystals doped with Au7 clusters and decorated with conjugated dyes as efficient triplet sensitizers or up-conversion applications (gold doping improves up-conversion efficiency). The beneficial effects of the doping strategy result in a maximum UC efficiency of 12%, which is an unprecedented result for up-conversion based on decorated NCs as triplet sensitizers.

Global energy consumption is expected to increase significantly together with the greenhouse gas emissions and the problem of fossil fuels exhaustion. Solar energy, as an alternative and renewable form of energy, has gained pop- ularity as possible solution for all these problems. Lots of materials have been studied to implement the energy conversion efficiency of the so-called third generation solar cells. These devices could be a cheaper alternatives to the silicon-based ones. Unfortunately, they are often characterized by short life- time or health hazardous materials. Bismuth sulfide(Bi2S3) is a promising n-type semiconductor for solar energy conversion.In this work,the properties of the compound will be discussed,as well as its potential for applications in solar energy technology.Wehave explored the colloidal synthesis of Bi2S3 nanocrystals,with the aim of employing them in the fabrication of solution- processable solar cells and to replace toxic heavy metals chalcogenides likePbS or CdS,that are currently employed in such devices. We compare different methods to obtain Bi2S3 colloidal quantum dots, including the useof environmentally benign reactants, through horganometallic synthesis. Surfactant-assisted colloidal synthesis(SACS) methods were used to synthesize Bi2S3 nanoparticles with different size and shape.These methods have been employed changing systematically several parameters such as temperature and timeofsynthesis, concentration ofchemical reagents and sulfur precursors. Morphological characteristics and optical properties of all the synthesized nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis and photoluminescence (PL) spectroscopy. After the characterization of electrical properties of bismuth sulfide sam- ples together with the preliminary attempts to find the most advantageous methods for the production of homogeneous film on conductive supports, asample was chosen like standard and it was employed in building of various prototype of third generation solution processed solar cells. Dip and spin coat- ing techniques were employed to produce homogeneous film of nanoparticleson conductive support, also in combination with organic polymer such P3HT, Pedot:PSS and Spiro-OMeTAD. The resulting solar cells were tested for power conversion efficiency (PCE). Synthesis and characterizations have been carried out in Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, under the supervision of Prof. Anna Musinu and Prof. Carla Cannas. Optoelectronic characterizations and solar cells manufacturing have been carried out in Di- partimento di Fisica, Università degli Studi di Cagliari, under the supervision of Prof. Michele Saba, Prof. Andrea Mura and Prof. Giovanni Bongiovanni.

Copper sulphide (CuxS, x = 1 to 2) is a metal chalcogenide semiconductor that exhibits useful optical and electrical properties due to the presence of copper vacancies. This makes CuxS thin films useful for a number of applications including infrared absorbing coatings, solar cells, thin-film electronics, and as a precursor for CZTS (Copper Zinc Tin Sulphide) thin films. Post-deposition sintering of CuxS nanoparticle films is a key process that affects the film properties and hence determines its operational characteristics in the above applications. Intense pulse light (IPL) sintering uses visible broad-spectrum xenon light to rapidly sinter nanoparticle films over large-areas, and is compatible with methods such as roll-to-roll deposition for large-area deposition of colloidal nanoparticle films and patterns. This paper experimentally examines the effect of IPL parameters on sintering of CuxS thin films. As-deposited and sintered films are compared in terms of their crystal structure, as well as optical and electrical properties, as a function of the IPL parameters.