Search

Oxidation of glycerol to lactic and glycolic acids is one of the most sought-after upgrades for this waste product in the biodiesel industry. These renewable glycerol-based hydroxy—carboxylic acid products are valuable monomers for the synthesis of new generation biodegradable polymers. In this work, a practically no-cost catalyst was prepared by using electrode coatings in 18,650 type Li-ion cells found in a spent DELL laptop battery. The combined cathode and anode coatings collected from Li-ion cells were pyrolyzed at 600 °C in air for 30 min. to prepare the catalyst with formula LiNi0.03Mn0.02Co0.11O0.85/C. Oxidation of glycerol using 25 mg/mmol catalyst in 0.50 M aqueous NaOH, under 3.4 atm. O2, 230 °C, 4 h. gave the highest yields of lactic and glycolic acids, 54 and 41%, respectively. Next, this hydroxy acid mixture was directly polymerized using p-toluene sulfonic acid—SnCl2 catalyst in refluxing xylene to give poly(lactic-co-glycolic acid) with Mw = 8017, Mw/Mn = 1.435, Tg = 41 °C, Tm = 182 °C and in 74% yield. [ABSTRACT FROM AUTHOR]

Faujasite (FAU) zeolites with abundant exchangeable sites are ideal hosts for the intake of Ag+ and the stabilization of highly luminescent silver nanoclusters (Ag NCs), while theoretical calculations on the spectral characteristics, charge states, and electronic energies of Ag NCs that are confined inside FAU zeolite were seldom reported. In this research, the Na-type FAU zeolites with varying silicon-to-aluminum (Si/Al) ratios were first synthesized with the hydrothermal method and then applied as matrixes to stabilize Ag NCs to obtain tunable emissions. With the decrease in the Si/Al ratio, the Ag NCs show red-shifted emission from 515 to 548 nm and broadened photoluminescence of excitation (PLE) and photoluminescence (PL) spectral profile. The time-dependent density functional theory (TD-DFT) method was carried out to probe the effect of Al substitution on the charge states and the optical properties of Ag NCs confined inside the double-six ring (D6r) cavity. The simulated results of the absorption spectra and energy levels suggest that the S1 → S0 transition of the monovalent Ag3+ cluster is responsible for the visible emission, and the increased full width at half-maximum (fwhm) of the PLE and PL spectra in the low Si/Al ratio FAU zeolites is due to the inhomogeneous broadening brought by the increased isomer numbers of the Al-substituted neutral zeolite framework. It is noted that the peak of the simulated absorption spectra red-shifted with the decrease in the Si/Al ratio, which is consistent with the experimental observation. This research provided an effective method for the manipulation of Ag NC emission in FAU zeolites through framework cation substitution and meanwhile theoretically explained the Si/Al ratio dependence of tunable emission properties, which may benefit the design of zeolite-confined Ag NCs with desirable optical performances. [ABSTRACT FROM AUTHOR]

In this research, upconversion nanocrystals incorporated with MOR zeolite composites were synthesized using the desilicated MOR zeolite as a host for the in situ growth of NaREF4 (RE = Y, Gd) Yb/Er nanocrystals. The structure and morphology of the composites were studied with XRD, XPS, and TEM measurements, and the spectral studies indicated that the subsequent thermal treatment can effectively improve the upconversion emission intensity of Er3+. By using the NaYF4:Yb/Er@DSi1.0MOR-HT composite that holds the strongest upconversion emission, a probe of UCNC@DSiMOR/BPEI was constructed with the modification of branched poly ethylenimine for the detection of Cu2+. It was indicated that the integrated emission intensity of Er3+ shows a linear dependence with the logarithm value of the Cu2+ concentration ranging from 0.1 to 10 μM. This study offered a feasible method for the construction of UCNC@zeolite composites with enhanced upconversion emission, which may have a potential application as fluorescent probes for the detection of various metal ions by adjusting the doping luminescent center. [ABSTRACT FROM AUTHOR]