Collision-Induced Dissociation of II−VI Semiconductor Nanocrystal Precursors, Cd²⁺ and Zn²⁺ Complexes with Trioctylphosphine Oxide, Sulfide, and Selenide

Abstract

The metal (M = Cd2+ and Zn2+) complexes with trioctylphosphine chalcogenide (TOPE, E = O, S, and Se) are prepared by electrospray ionization, and their relative stabilities and intramolecular reactions are studied by collision-induced dissociation (CID) with Xe under single collision conditions. These metal-TOPE complexes are considered as molecular precursors for the colloidal synthesis of II-VI compound semiconductor nanocrystals employing TOPO as a metal-coordinating solvent and TOPS or TOPSe as a chalcogen precursor. Of the various [M + nTOPE]2+ (n = 2-7) ions generated by ESI, the n = 2-4 complexes are characterized by CID as a function of collision energy. The collision energy at 50% dissociation (E50%) is determined from the cracking curve and the relative stabilities of the complexes are established. Between the two metal ions, the zinc-TOPE complexes are more stable than the cadmium-TOPE complexes when n = 2-3, whereas their stabilities are reversed when n = 4. Of the TOPE, TOPO binds most strongly to the metal ion, while TOPSe does most weakly. Upon CID, loss of TOPE occurs exclusively from the tetra-TOPE complexes, while extensive fragmentation of TOPE takes place from the di-TOPE complexes, showing the signature of the metal chacogenide formation. The nucleation of nanocrystals appears to begin with cracking of [M + 2TOPE]2+ (E = S and Se).

Noncovalent Binding between Fullerenes and Protonated Porphyrins in the Gas Phase

“…Experiments were carried out using a hybrid triple quadrupole/ reflectron time-of-flight (TOF) mass spectrometer (QSTAR Pulsar-i, MDS Sciex, Concord, Canada) equipped with a nanospray ionization source, as previously described in detail. 25 A 1-µm-i.d. Au/Pd-coated borosilicate glass tip (Proxeon, Odense, Denmark) was used to spray the sample into the mass spectrometer.…”

Infrared reflectance and transmission spectra in II-VI alloys and superlattices

“…Optoelectronic devices based on II-VI compound semiconductor alloys and their multilayer structures are generally composed of various thin homo-or heterofilms of different thicknesses, compositions, and doping levels. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Such novel metastable materials, unavailable in nature, are being prepared by modern epitaxial growth techniques. [34][35][36][37][38][39][40][41][42] Understanding their physical properties in the context of controlling parameters (viz.…”

“…The optical, structural, and electrical properties of luminescent II-VI compound semiconductors [1][2][3][4][5][6][7][8][9][10][11][12][13][14] with bandgap energies ranging from 0 to 4 eV are appealing for ultrasensitive multiplexing/multicolor applications in a variety of emerging areas of biotechnology, nanoscale optoelectronics, and nanophotonics. [8][9][10][11][12][13][14] By varying the composition and controlling the lattice constants in ternary or quaternary alloys, we can achieve greater flexibility of tuning emission and absorption wavelengths for high-efficiency solid-state light emission sources.…”

Structural and dynamical properties of Bridgman-grown CdSexTe1−x(0<x≤Talwar1, Feng2, Lee3 et al. 2013Phys. Rev. B171110View full textAdd to dashboardCite

“…Cd-based compound semiconductors with high optical absorption coefficients (>5 × 10 5 /cm) and direct band gaps (1.474-2.5 eV) are apposite for engineering integrated microelectronic, sensor, spintronic, photonic, photovoltaic, piezoelectric, and optoelectronic devices. [1][2][3][4][5][6][7][8][9][10] Unlike, most II-VI materials, the Cd chalcogenides (CdS, CdSe, and CdTe) exhibit either in the zinc-blende (zb) and wurtzite (wz) crystal structures or in mixed zb/wz phases with varied degrees of ionic/covalent bonding. Earlier use of II-VI compounds [11][12][13][14][15][16][17][18][19][20] for the fruition of blue-green light-emitting diodes (LEDs) was hampered by the nonavailability of good-quality crystals and difficulties of managing doping.…”

“…Depending upon the growth conditions, it is possible to stabilize one of the two crystal structures either by strain, choosing proper substrates and/or buffer layers, or by controlling the growth temperatures. [1][2][3][4][5][6][7][8][9][10] Thin CdS or CdSe epilayers are now grown in the zb phase which does not exhibit the lowest-energy configuration in the bulk. 33 Despite technological significance of II-VI materials, the prevailing information on their fundamental properties is either sparse or contradictory.…”