This work presents the influence of the reproducibility, stability and the morphology of silver nanoparticles (AgNPs) obtained by green synthesis of nanoparticles (GNPs) assisted by a
Mentha spicata
...extract solution as reducing stock solution (RSS). Noteworthy colloidal dispersion at 6.4 months has been reported by the presence of the surface plasmon resonance (SPR) in the UV–Vis spectra for spherical nanoparticles (680AgN), while quasi-spherical nanoparticles (1300AgN) presented aggregation. Thereby, a great amount of RSS as reducing agent present in the synthesis involves the formation of NPs (nanoparticles) with tendency to agglomeration as shown by high-resolution transmission electron microscope (HRTEM) and Z potential for 1300AgN system. Meantime, the Fourier transform infrared spectroscopy (FTIR) spectra supported that hydroxy group of the poly phenols species reported at 3420 cm
−1
, and the C=C bonds presented in the aromatic rings at 1633 cm
−1
are the main electron-donating species to obtain AgNPs. Finally, the performance of the AgNPs systems to the reduction of 4-nitrophenol (4-NP) was evaluated in the presence of sodium borohydride (NaBH
4
). These outcomes show NPs with ordered morphology by GNPs reproducible and, with outstanding colloidal stability without an external stabilizer agent, at natural pH of the NPs, and they are useful to diverse applications.
Graphical abstract
The present work reports the changes for the mesoporous materials SBA-15 and KIT-6 associated with the structural, textural, and chemical properties when they are subjected to thermo-alkaline ...treatment. Despite the fact that the silica supports have not a strong affinity for CO
2
adsorption, the adsorption enthalpy profiles (ΔH
ads
) reported that the substrates subjected to the thermo-alkaline treatment (S15H and K6H) have a greater energetic affinity towards CO
2
capture if compared to the precursory solids (S15 and K6). The ΔH
ads
is − 26.7 kJ mol
−1
at 0.15 mmol g
−1
by supported S15H and K6H while the ΔH
ads
is − 20. 7 kJ mol
−1
and − 18.7 kJ mol
−1
by K6 and S15, respectively, at the same CO
2
coverage. Furthermore, the CO
2
adsorption performances by the hydrolytic condensation between silica supports and the N´- (3-trimethoxysilylpropyl)diethylenetriamine (NAEPTES) or 3-aminopropiltriethoxysilane (APTES) are presented and it can be seen that the best performer for CO
2
adsorption is reported for the S15HN since it is able to absorb 0.93 mmol at 0.15 atm at 318 K. Thereby, the outcomes show that the effects of porous curvature and the magnitude of the amine species are parameters to be considered, as well as the thermo-alkaline treatment, in order to improve the subsequent surface reactions on silica supports. The materials were characterized by XRD, TEM, and N
2
adsorption at 77 K, NIR, and pyridine thermodesorption using Fourier Transform Infrared Spectroscopy (FTIR-Py), NMR for
29
Si and
13
C, DSC, and CO
2
adsorption.
Graphical abstract
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•Improvements in the synthesis of aluminum metal–organic framework.•Optimization of solvothermal and green routes.•The solvothermal synthesis avoids the use of modulators.•Production ...of hexagonal bifrustum-shaped crystals.•Carbon dioxide performance and adsorption enthalpy.
Synthetic routes to produce metal–organic frameworks (MOFs) utilizing a sustainable method and the smallest amount of toxic organic solvents are desirable to avoid problems associated with chemical waste liquids. Herein, we report the synthesis of an aluminum trimesate-based MOF, MIL-96-(Al), under solvent-free conditions. Moreover, novel syntheses by reflux and solvothermal methods are described. All the synthetic routes yielded pure crystalline MIL-96-(Al). Solvent-free synthesis was achieved within 4 h, providing an improvement over current literature methods. Solvothermal synthesis prepared in mixed solvents allowed superior quality of hexagonal bifrustum MIL-96-(Al) crystals without surfactants or modulators, as those found in previous reports. Furthermore, reflux methodology was performed in attempts to scale up the yielding of solids. However, the scanning electron microscopy images exhibited variations in morphology, and at least three crystal shapes were observed. The carbon dioxide (CO2) adsorption properties of MIL-96(Al) samples were evaluated to determine the enthalpy of adsorption (ΔHads) of CO2. In the four synthetic routes explored, the CO2 adsorption behavior of MIL-96-(Al)-ST synthesized by the solvothermal route is the most promising, exhibiting a constant value of ΔHads of −30 kJ mol−1, suggesting that the chemical environment and well-defined bifrustum shape of MIL-96(Al) crystals, could play an important role in the diffusion of CO2.
Special preparation of Santa Barbara Amorphous (SBA)-15, mesoporous silica with highly hexagonal ordered, these materials have been carried out for creating adsorbents exhibiting an enhanced and ...partially selective adsorption toward CO₂. This creation starts from an adequate conditioning of the silica surface, via a thermo-alkaline treatment to increase the population of silanol species on it. CO₂ adsorption is only reasonably achieved when the SiO₂ surface becomes aminated after put in contact with a solution of an amino alkoxide compound in the right solvent. Unfunctionalized and amine-functionalized substrates were characterized through X-ray diffraction, N₂ sorption, Raman spectroscopy, electron microscopy,
Si solid-state Nuclear Magnetic Resonance (NMR), and NH₃ thermal programmed desorption. These analyses proved that the thermo-alkaline procedure desilicates the substrate and eliminates the micropores (without affecting the SBA-15 capillaries), present in the original solid. NMR analysis confirms that the hydroxylated solid anchors more amino functionalizing molecules than the unhydroxylated material. The SBA-15 sample subjected to hydroxylation and amino-functionalization displays a high enthalpy of interaction, a reason why this solid is suitable for a strong deposition of CO₂ but with the possibility of observing a low-pressure hysteresis phenomenon. Contrastingly, CH₄ adsorption on amino-functionalized, hydroxylated SBA-15 substrates becomes almost five times lower than the CO₂ one, thus giving proof of their selectivity toward CO₂. Although the amount of retained CO₂ is not yet similar to or higher than those determined in other investigations, the methodology herein described is still susceptible to optimization.
Synthesis and adsorption studies of the SBA-15 immobilizing perylene and pyrene dyes are described in this work. The functionalization is carried out with amine groups through post-synthesis using ...amino-propyl triethoxysilane (APTES) and ethanol or toluene as solvent. The resulting functionalized material is investigated as a matrix for the immobilization of perylene-3,4,9,10-tetracarboxylic dianhydride (PDA). Further exploration of the immobilization of 1-Pyrenecarboxaldehyde (PCA) is detailed. The obtained materials were characterized by FTIR and fluorescence spectroscopy, nitrogen adsorption analysis and X-ray diffraction (XRD). The textural characterization of the functionalized samples shows the decrement of the average pore sizes and the surface area as consequence of the APTES and fluorescent dyes immobilization. Compared with the pristine SBA-15, the solids obtained by functionalization with PDA yielded red-coloured samples, which show absorption bands at λ = 670 nm in solid state and λ = 570 nm in solution. The PDA dye is bonded to the SBA-15 network and it shows absorption or emissions properties for the new hybrid solids. The fluorescence of these species are preserved if the PDA molecules remains with a more flexible structure.
A sol-gel methodology has been duly developed in order to perform a controlled covalent coupling of tetrapyrrole macrocycles (e.g., porphyrins, phthalocyanines, naphthalocyanines, chlorophyll, etc.) ...to the pores of metal oxide networks. The resulting absorption and emission spectra intensities in the UV-VIS-NIR range have been found to depend on the polarity existing inside the pores of the network; in turn, this polarization can be tuned through the attachment of organic substituents to the tetrapyrrrole macrocycles before bonding them to the pore network. The paper shows clear evidence of the real possibility of maximizing fluorescence emissions from metal-free bases of substituted tetraphenylporphyrins, especially when these molecules are bonded to the walls of functionalized silica surfaces via the attachment of alkyl or aryl groups arising from the addition of organo-modified alkoxides.
The presence of toxic substances constitutes an environmental problem and even affects health. To evaluate the photoreduction of 4-nitrophenol (4-NF) and Cr(VI), both highly polluting substances, two ...Zn materials synthesized by the precipitation method; ZnS (Zinc Sulfide) and ZnS/ZnO-tubes (Zinc Sulfide deposited on Zinc Oxide tubes) have been used. The ZnS/ZnO-tubes assisted photoreduction of 4-NP to 4-aminophenol (4-AP) exhibits pseudo-first order kinetics with a rate constant of 0.1476 min
−1
and a yield of 90% at 15 min, while the ZnS material exhibits zero-order kinetics with a rate constant of 0.07859 mg/L*min and a reducing yield of 30% at 15 min. However, for the Cr(VI) to Cr(III) photoreduction reaction they exhibit pseudo-second-order kinetics with a rate constant of 2.711 L/mg*min accompanied by a 90% reducing yield at 15 min in the presence of ZnS/ZnO tubes, and pseudo-zero-order kinetics with a rate constant of 0.518 mg/L*min and a 30% reducing yield at 15 min for the ZnS material. In both cases, the hybrid ZnS/ZnO-tubes material exhibits exceptional catalytic performance. The photocatalytic efficiency of the ZnS/ZnO-tubes material is cooperatively attributed to its morphological and chemical properties. The average particle size of ZnS/ZnO-tubes is 150 nm, while that of ZnS particles is 450 nm.
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