Electropolymerized film of 3,3′,3″,3‴-tetraaminophthalocyanatonickel(II) (p-Ni
IITAPc) on glassy carbon (GC) electrode was used for the selective and stable determination of 3,4-dihydroxy-
...l-phenylalanine (
l-dopa) in acetate buffer (pH 4.0) solution. Bare GC electrode fails to determine the concentration of
l-dopa accurately in acetate buffer solution due to the cyclization reaction of dopaquinone to cyclodopa in solution. On the other hand, p-Ni
IITAPc electrode successfully determines the concentration of
l-dopa accurately because the cyclization reaction was prevented at this electrode. It was found that the electrochemical reaction of
l-dopa at the modified electrode is faster than that at the bare GC electrode. This was confirmed from the higher heterogeneous electron transfer rate constant (
k
0) of
l-dopa at p-Ni
IITAPc electrode (3.35
×
10
−2
cm
s
−1) when compared to that at the bare GC electrode (5.18
×
10
−3
cm
s
−1). Further, it was found that p-Ni
IITAPc electrode separates the signals of ascorbic acid (AA) and
l-dopa in a mixture with a peak separation of 220
mV. Lowest detection limit of 100
nM was achieved at the modified electrode using amperometric method. Common physiological interferents like uric acid, glucose and urea does not show any interference within the potential window of
l-dopa oxidation. The present electrode system was also successfully applied to estimate the concentration of
l-dopa in the commercially available tablets.
Amorphous carbon nitride a-CN0.26 thin films were elaborated on transparent and conductive glass/indium-tin oxide (ITO) wafers to improve the electroanalytical detection of transthyretin peptide (PN) ...and specific amino acids (AA) from its sequence, which constitutes a great challenge for the diagnosis of transthyretin-related familial amyloïd polyneuropathy (ATTR). The naphthalene-2,3-dicarboxyaldehyde (NDA) label was used for the derivatization reaction of PN and AAs to form N-2-substituted-1-cyanobenz-f-isoindole derivatives (CBI) which are both fluorescent and electroactive. The results obtained on a-CN0.26 were compared with those observed on glassy carbon (GC) as a reference material. It was shown that a soft anodic pre-treatment protocol on glass/ITO/a-CN0.26 electrode in a KCl aqueous solution drastically improved the performances of the CBI-PN and CBI-AA oxidation peak. The oxidation peak potential for all CBI derivatives varied in the same range than those measured on GC and pre-treated glass/ITO/a-CN0.26, while no discrimination could be obtained on as-grown glass/ITO/a-CN0.26 electrodes. For almost all the tested CBI derivatives, peak areas, full-widths at peak mid-height, peak current density and their standard deviation (SD) values were improved on a pre-treated a-CN0.26 electrode in comparison with GC.
•Autoclave extraction with supercritical carbon dioxide for lithium ion battery electrolytes.•Investigations on the extraction behavior.•Extraction of aging products and identification of several ...products with different methods (GC, IC).
Two different separator materials (polyethylene fleece – Freudenberg 2190 and porous glass fiber – Whatman® GF/D) and two different lithium-ion battery electrolytes have been investigated regarding their behavior in an autoclave extraction with supercritical helium head pressure carbon dioxide (sc HHPCO2). Mixtures of dimethyl carbonate (DMC)/ethylene carbonate (EC) and ethylmethyl carbonate (EMC)/EC, each with 1mol/L LiPF6 were used.
In addition to these proof of principle experiments, the developed extraction method was further applied to real battery samples. Commercial 18650cells (after formation and aging) were opened and the jelly roll was extracted with sc HHPCO2. Extracts were analyzed with gas and ion chromatography (GC, IC). Recovery rates and extract compositions strongly depend on the material of which the electrolyte is extracted. Further structure determination of electrolyte aging products was performed with different ionization modes in GC–mass spectrometry (GC–MS) experiments. Diethyl carbonate (DEC), dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC), ethylmethyl-2,5-dioxahexane dicarboxylate (EMDOHC) and diethyl-2,5-dioxahexane dicarboxylate (DEDOHC) are aging products of electrolyte degradation which were successfully extracted and identified. Their concentrations correlate with solid electrolyte interphase (SEI) growth on the negative electrode which was investigated with scanning electron microscopy (SEM).
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•Cation substitution in YAG induced the tunability of Mn4+ excitation and emission.•The prepared phosphor exhibited bright red emission with quantum yield of 42%.•Color tunable ...dual-phase glass ceramic was successfully fabricated.•Improved optoelectronic performance for the GC-based WLED was demonstrated.
Recently, Mn4+ doped oxide red phosphors have been attracted great attention for promising application in white light-emitting diode to improve optoelectronic properties. Unfortunately, most of Mn4+ doped oxide phosphors suffer from low absorption/excitation in blue light region and deep red emission. In this work, taking Y3Al5O12 as the Mn4+ doped host, we demonstrate the tunability of excitation and emission of Mn4+ activator via cation substitution. X-ray diffraction patterns confirm that Y3+ and Al3+ in the host can be completely replaced by Gd3+/Lu3+ and Ga3+, respectively. Impressively, the substitution of Al3+ ions by Ga3+ ones is beneficial to significantly enhance Mn4+4A2→4T2 blue excitation band and shift 2E→4A2 red emission band toward low-energy region; the replacement of Y3+ by Gd3+ induces red-shifting of both Mn4+ excitation and emission bands while Lu3+ doping leads to the opposite result. These phenomena may be attributed to the doping-induced alteration of Mn4+ local environments, i.e., the covalency of Mn4+ ligand field. Finally, inorganic Ce3+: Y3Al5O12 and Mn4+: Y3Al5O12 dual-phase embedded glass ceramic is prepared by a low-temperature co-sintering route to replace phosphors in organic silicone as color converter, and by combining the synthesized glass ceramic with InGaN blue chip, warm white light-emitting diode with superior optical performance is successfully realized.
Bioactive glass and glass-ceramics have a huge interest in biomedical application due to their high biocompatibility and bioactive property. In this study, macro porous glass-ceramic based on 51.26% ...SiO2 - 36.56% CaO - 11.83% P2O5 and 42.11% SiO2 - 18.42% CaO - 29.82% Na2O - 9.65% P2O5 (in mol%) were prepared via sol-gel synthesis and powder sintering method. Sodium nitrate was used as the precursor for sodium oxide (Na2O) composition in the sol-gel glass. Effect of sodium nitrate addition on the sintered glass (glass-ceramic) properties were studied. The stabilized gel-glasses obtained were compacted into pellets and sintered at 1000 °C for 3 hours. It was found that, Na-contained glass-ceramic (Na-GC) crystallized at 71.5% due to increase in sodium-related crystalline phases. Na-GC showed 72.98% of apparent porosity and densified at 27.02% with macro porous structure with pore sizes in the range of 22.4 μm to 302 μm. The macro porous structure of Na-GC was obtained due to the foaming effect occurred during sintering. Flux effect occurred during sintering also resulted in relatively high compressive strength of Na-GC at 21.53 MPa. The macro porous Na-GC also proved to be bioactive as apatite-like structures were deposited on its surface after immersed into SBF solution for 14 days. The prepared macro porous Na-GC has high potential to be used as a scaffold material in biomedical application due to combination of suitable macro-pore size range, bioactive and has sufficient mechanical strength.
Rapid, comprehensive two-dimensional gas chromatographic (GC × GC) separations by use of a microfabricated midpoint thermal modulator (μTM) are demonstrated, and the effects of various μTM design and ...operating parameters on performance are characterized. The two-stage μTM chip consists of two interconnected spiral etched-Si microchannels (4.2 and 2.8 cm long) with a cross section of 250 × 140 μm2, an anodically bonded Pyrex cap, and a cross-linked wall coating of poly(dimethylsiloxane) (PDMS). Integrated heaters provide rapid, sequential heating of each μTM stage, while a proximate, underlying thermoelectric cooler provides continual cooling. The first-dimension column used for GC × GC separations was a 6 m long, 250 μm i.d. capillary with a PDMS stationary phase, and the second-dimension column was a 0.5 m long, 100 μm i.d. capillary with a poly(ethylene glycol) phase. Using sets of five to seven volatile test compounds (boiling point ≤174 °C), the effects of the minimum (T min) and maximum (T max) modulation temperature, stage heating lag/offset (O s), modulation period (P M), and volumetric flow rate (F) on the quality of the separations were evaluated with respect to several performance metrics. Best results were obtained with a T min = −20 °C, T max = 210 °C, O s = 600 ms, P M = 6 s, and F = 0.9 mL/min. Replicate modulated peak areas and retention times were reproducible to <5%. A structured nine-component GC × GC chromatogram was produced, and a 21 component separation was achieved in <3 min. The potential for creating portable μGC × μGC systems is discussed.
Bioactive glass–ceramic powder reinforced alginate scaffold has been successfully prepared and characterized for bone tissue engineering application. Glass-ceramic (GC) particles were synthesized ...through a sol–gel process. Alginate scaffolds containing different weight percentages of GC were fabricated through a freeze-drying technique. The composite scaffolds were characterized for phase analysis through X-ray powder diffraction and microstructure analysis through field emission scanning electron microscopy. The swelling behavior, degradation behavior, bioactivity, cell adhesion, and osteogenic potential of the fabricated scaffolds were evaluated. Microstructural analysis showed a highly porous behavior of the scaffold having a macroporous pore size. The composite scaffolds showed good bioactivity where GC induces apatite formation. The compressive strength of the scaffold was enhanced with GC addition due to the reinforcement of the alginate matrix. In vitro cell studies revealed that the composite scaffolds promoted cell adhesion, proliferation, and osteogenesis. Fabricated scaffolds are a promising biomaterial candidate for bone substitution because of their attractive properties.
Crystal growth kinetics and liquid dynamics of 1,2-diphenylcyclopentene (DPCP) and 1,2-diphenylcyclohexene (DPCH) were characterized by optical microscopy and dielectric spectroscopy. These two ...molecules are structurally homologous and dynamically similar to the well-studied glassformer ortho-terphenyl (OTP). In the supercooled liquid states of DPCP and DPCH, the kinetic component of crystal growth u kin has a power law relationship with the primary structural relaxation time τα, u kin ∝ τα –ξ (ξ ≈ 0.7), similar to OTP and other fragile liquids. Near the glass transition temperature (T g), both DPCP and DPCH develop much faster crystal growth via the so-called GC (glass to crystal) mode, again similar to the behavior of OTP. We find that the α-relaxation process apparently controls the onset of GC growth, with GC growth possible only at sufficiently low fluidity. These results support the view that GC crystal growth can only occur in systems where the liquid and crystal exhibit similar local packing arrangements.
We developed a new bioactive glass-ceramic (GC) based on the CaO-SiO2-MgO-Na2O-Li2O system. Four glass compositions were formulated by a proprietary software (Reformix) and tested by changing mainly ...the calcium content (from 20 mol% to 40 mol%) and the minor components - alumina, zirconia and zinc oxide. We produced our GCs using the sinter-crystallization process at different temperatures (800–1000 °C) and evaluated the effects of compositional changes on the sintering kinetics, microstructure (residual porosity and crystalline phases), hardness, bending strength and bioactivity. We then followed the hydroxycarbonate apatite (HCA) formation in simulated body fluid by Fourier-transform infrared spectroscopy (FTIR), which revealed the onset of HCA formation after approximately 3 days. These GCs are phosphorus and fluorine free, elements that are present in most bioactive glasses, glass-ceramics and ceramics. Our most bioactive GC has a residual porosity of 9 ± 1%, hardness of 5.5 ± 0.3 GPa, 4p-bending strength of 98 ± 7 MPa and is non-cytotoxic. This combination of good bioactivity and mechanical properties (despite its high porosity) suggests that this new GC could be tested for bone graft implants.
This study investigated the compressive strength, drying shrinkage and alkali-silica reaction (ASR) expansion of alkali-activated mortars using sand or glass cullet (GC) as aggregates and using glass ...powder (GP) to partially replace ground granulated furnace slag (GGBS) as the precursor. For mortars using GC as the aggregate, the replacement of GGBS by GP decreased the compressive strength. The mortars using sand as aggregate showed severe drying shrinkage and the replacement of sand by GC could significantly decrease the drying shrinkage. The addition of calcium aluminium cement (CAC) could further suppress the drying shrinkage. The alkali-activated GGBS mortars using GC as the aggregate showed large expansion after alkaline immersion. When using GP to partially replace GGBS, the expansion was significantly decreased. The replacement of 15% GGBS by CAC could further decrease the expansion. The optimal alkali-activated cement (AAC) mixture proportion developed in this study was the mortars incorporating 15% of CAC, 10% of GGBS and 75% of GP as the compressive strength, expansion and drying shrinkage of this mixture could meet the stipulated mechanical and durability requirements for partition wall applications.
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