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All-Optical Plasmonic Modulators and Interconnects
Published in Sergey I Bozhevolnyi, Plasmonic, 2019
Domenico Pacifici, Henri J. Lezec, Luke A. Sweatlock, Chris de Ruiter, Vivian Ferry, Harry A. Atwater
We fabricated several on-chip planar interferometers consisting of a single subwavelength aperture flanked by a subwavelength groove in a metal film. Identical subwavelength structures were fabricated by focused ion beam (FIB) milling into a 400 nm thick layer of Ag evaporated onto flat fused silica microscope slides. A low beam current (50 pA) was used to achieve surface features defined with a lateral precision of the order of 10 nm and characterized by near-vertical sidewalls and a minimal amount of edge rounding. The milled groove and slit were 10 μm long, 200 and 100 nm wide, and 100 nm and 400 nm deep, respectively. The slit-groove separation distance was systematically varied in the range 500–10400 nm, in step of 50 nm, with a precision of 1%. A series of single apertures is also milled for reference purposes. The same set of structures was milled in another silver film (co-evaporated with the previous sample) which was previously spin-coated with a thin film of densely-packed CdSe QDs obtained by colloidal chemical synthesis in solution.28 The QDs were capped with trioctylphosphine oxide (TOPO) ligands. Multiple spin-coatings of the toluene solution containing CdSe QDs were performed at 1000 rpm for 1 minute, followed by a thermal treatment at 150°C for 5 minutes. A 24 nm-thick film of densely-packed CdSe QDs was formed, with a good uniformity over the entire silver surface. The QDs showed bright photoluminescence (PL) peaked at 625 nm.
Synthetic and Therapeutic Development of Spherical Nucleic Acids
Published in Costas Demetzos, Stergios Pispas, Natassa Pippa, Drug Delivery Nanosystems, 2019
Stanislav Rangelov, Ivaylo Dimitrov
QD SNAs were first synthesized in 1999 by covalently attaching oligonucleotides directly to the QD core [11]. Initially, CdSe QDs were stabilized with trioctylphosphine oxide and trioctylphosphine followed by surface modification with 3-mercaptopropionic acid. After the surface carboxylic group deprotonation with 4-(dimethylamino)pyridine, QDs were readily dispersed in water and were able to immobilize thiol-terminated oligonucleotides. Later, a method for noncovalent immobilization of ssDNA on the surface of aliphatic ligand–protected CdSe/ZnS QDs by reacting them with amphiphilic polymers functionalized with DNA was reported [12]. Briefly, oleylamine-protected CdSe/ZnS core/shell QDs were modified with an amphiphilic polymer containing both hydrophobic alkyl chains (which intercalated with the hydrophobic capping ligands on the NP) and hydrophilic polyethylene glycol–bearing clickable end group. The particles were then functionalized with DNA applying click chemistry to produce a dense DNA shell. Fluorophore-labeled oligonucleotide QD SNAs were used to follow the intracellular events that occur following their cellular uptake [39].
Inorganic Nanomaterials
Published in Wesley C. Sanders, Basic Principles of Nanotechnology, 2018
Another common quantum dot synthesis involves the use of molecular precursors (Pradeep 2007). This method involves the preparation of nanocrystalline seeds in a material controlling the growth of particles via chemical coordination (Pradeep 2007). Chemical coordination involves the binding of ligands (atoms, ions, or molecules) to metal centers where ligand atoms donate electrons to the metal centers. Trioctylphosphine oxide (TOPO) is used exclusively for this method of synthesis (Pradeep 2007). TOPO is used because it coordinates with inorganic materials and can undergo an exchange reaction with other ligands (Pradeep 2007). As the reaction proceeds, the particles grow to form monodisperse structures (Pradeep 2007). This method involves the injection of metal ion precursors into hot TOPO with continuous stirring (Figure 6.8) (Pradeep 2007). Oftentimes, a compound that contains the constituent elements and semiconductors is used in this type of synthesis (Pradeep 2007). For instance, Cd(S2CNEt2)2 is used to produced cadmium sulfide (CdS) quantum dots (Pradeep 2007).
Developed procedure for Sn (II) extraction from hydrochloric acid medium with CYANEX 921 and its recovery from spent LCD screens
Published in Chemical Engineering Communications, 2022
S. E. Rizk, B. A. Masry, J. A. Daoud
Chemicals and reagents used in the current study are of analytical reagent grade (AR) and were used as received without further purification. HCl, H2SO4, NaCl, HNO3 and other chemicals are products of British Drugs House (BDH). CYANEX 921 belongs to the family of solvating extractants developed by Cytec and contains mainly (93% trioctylphosphine oxide) ((C8H17)3 P = O). Stannous chloride and indium chloride are products of Sigma Aldrich and were dissolved in 3 M HCl to obtain the required Sn(II) and In(III) concentration. The non-aromatic odorless kerosene used as diluent was purchased from Misr Petroleum Ltd Company, Cairo, Egypt which has (density = 0.8 g/ml, boiling point = 175–325 °C, dipole moment = 2 and molecular formula as C9-C16 hydrocarbon). the ASTM D86 curve for kerosene Figure 1 which is plotted between the simulated volumetric flow rates and their corresponding temperatures indicate that the experimental values were slightly different from standard values which elucidated that light fraction such as kerosene does not require further processing or purification steps after the crude distillation unit (CDU) (Hasibul et al. 2015).
A comparative study of the solvent extraction of lanthanum(III) from different acid solutions
Published in Mineral Processing and Extractive Metallurgy, 2021
V. Agarwal, M.S. Safarzadeh, J. Galvin
Organophosphorus-type extractants are commonly used for the solvent extraction of REEs. Among the many possible extractants, di-(2-ethylhexyl)phosphoric acid (DEHPA), PC88A, and di-2,4,4-trimethylpentylphosphinic acid (Cyanex 272) are perhaps the most popular extractants for REEs. Peppard et al. (1958) investigated the extraction behaviour of lanthanides with several acidic esters of organophosphorus extractants and found that the distribution coefficients followed an inverse third power dependency on the concentration of H+ and a direct third power dependency on the concentration of the extractant. Saleh et al. (2002) investigated the solvent extraction of La(III) with Cyanex 272 diluted in toluene with and without trioctylphosphine oxide (TOPO) in nitrate-acetate medium. They observed that, at a high concentration of La(III), a white precipitate (LaA3) formed, affecting the distribution ratio (D) significantly. It was concluded that the complexes extracted into the organic phase were La(Ac)2A.3HA and La(Ac)2A2.B, respectively, in the absence and presence of TOPO. Morais and Ciminelli (2004) investigated the recovery of La(III) using DEHPA and PC88A in Exxsol™ (purified kerosene) from HCl solutions. They suggested that DEHPA performed better than PC88A in terms of extraction of La(III) but the selectivity of La(III) over Pr(III) and Nd(III) was better with PC88A than DEHPA.
Dimerization of 2-Ethylhexylphosphonic Acid Mono-2-ethylhexyl Ester (HEH[EHP]) as Determined by NMR Spectrometry
Published in Solvent Extraction and Ion Exchange, 2021
Ashleigh Kimberlin, Kenneth L. Nash
The HEH[EHP] (Carbosynth and eNovation Chemicals) was purified using the third-phase method, as described previously.[21] HDEHP was purified using the copper purification method.[22] The purity of HEH[EHP]and HDEHP was verified using 1H and 31P NMR and each was determined to be at least 98% pure. Trioctylphosphine oxide (TOPO, Sigma Aldrich) was also purified of acidic impurities by contacting a 0.5 M solution of TOPO in toluene with a 0.5 M solution of sodium bicarbonate. The organic solution was contacted with 18 MΩ cm−1 DI water to remove excess sodium bicarbonate and the solution was dried with magnesium sulfate. Triphenylphosphine oxide (Alfa Aesar. 98%), 18-crown-6 (Fluka, 99.5%), anthracene (Eastman Organic Chemicals), 1,3-diisopropylbenzene (Alfa Aesar, 96%), decalin (Sigma Aldrich, 98% cis and trans), toluene (Fisher 99.9%), tributyl phosphate (Fisher), and n-dodecane (Sigma Aldrich, 99%) were used as received. Structures of chemicals used are reported in Figure 1. Concentrated nitric acid (EMD) was used as received. Lu(NO3)3 solutions were made by dissolving Lu2O3(s) with nitric acid and Lu(NO3)3 solutions were standardized via cation exchange/acid titration. Stock solutions of Lu3+ were then diluted as needed without further standardization.