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Non-destructive assessment of the oxidative stability of intact macadamia nuts during the drying process by near-infrared spectroscopy
摘要： We have developed a rapid non-destructive method to assess the oxidative stability of intact macadamia nuts using near-infrared spectroscopy (NIRS). Intact macadamia nuts of the cultivars HAES 344 'Kau', HAES 660 'Keaau', IAC 4-12 B, and IAC Campinas B were harvested and immediately oven-dried for 4 days at 30 °C, 2 days at 40 °C, and 1 day at 60 °C to achieve 1.5% kernel moisture content. At each drying step nuts were withdrawn and their moisture content, peroxide value (PV), and acidity index (AI) determined. The best partial least square model for PV prediction was obtained using the Savitzky-Golay (SG) second derivative resulting in a standard error of prediction (SEP) of 0.55 meq·kg?1 and a coefficient of determination (R2 C) of 0.57. The best AI prediction-model result was obtained using the SG second derivative (SEP = 0.14%, R2 C = 0.29). Based on the maximum quality limits of 3 meq·kg?1 for PV and 0.5% for AI, the SEP values represented 18% and 28%, respectively. Therefore, the prediction method can be considered useful since the errors are lower than the quality limits. Thus, NIRS can be used to assess the oxidative stability of intact macadamia kernels.
关键词： principal component analysis,peroxide value,Macadamia integrifolia Maiden & Betche,acidity index
更新于2025-09-23 15:23:52
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Cu and Zr surface sites in photocatalytic activity of TiO2 nanoparticles: The effect of Zr distribution
摘要： The present work is focused on the role of ZrO2 modification in the performance of CuO modified TiO2. Zirconia loading leads to formation of more resistant photocatalytic layers compared to samples modified with only copper containing species. Surface modification of mixed phase TiO2 with CuO/ZrO2 improves the degradation of Reactive blue 19 dye under simulated solar irradiation. An in-depth investigation of the catalysts showed that in case of CuO/ZrO2 modification, the covering of the TiO2 surface with zirconium containing species prevents morphological and harmful energetic changes induced by copper species formed on the rutile TiO2 phase at a higher copper loading.
关键词： Hammett indicators,titanium dioxide,surface modification,XAS analysis,surface acidity
更新于2025-09-23 15:23:52
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Towards More Effective, Reversible pH Control by Visible Light Alone: a Thioindigo Photoswitch Undergoing a Strong pKa Modulation by Isomer Specific Hydrogen Bonding
摘要： We have synthesized and characterized a thioindigo photoswitch featuring phenolic residues forming an intramolecular H bond exclusively in the cis isomer. In acetone water mixtures, wavelength dependent photostationary states their extremes of up to 95 % and down to 11 % cis isomers at ca. 580 and 480 nm, respectively. Within a few hours, room temperature thermal isomerization is negligible in neutral and mildly acidic solutions. Protic media decrease trans→cis but increase cis→trans quantum yields. In CD3OD solution, in which light of any wavelength absorbed triggers the latter process almost exclusively, 19F NMR titration provides pKa values of 7.2 (trans) and 5.0 (cis; both rescaled to water) corresponding to a change in dissociation constant of 2.2 orders of magnitude. Future derivatives featuring solubility and reversible photochromism in plain water may provide pH modulation of similar amplitude in a range adjustable by the choice of phenolic substituents.
关键词： thioindigo,acidity,kinetics,hydrogen bonds,photochromism
更新于2025-09-23 15:21:01
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Optical properties of soil DOM are related to acidic functions of its components as revealed by fractionation, selective deuteromethylation and ultra-high resolution mass spectrometry
摘要： The goal of this study was to establish relationship between the optical properties of soil dissolved organic matter (DOM) and acidic functions carried by its individual constituents. We obtained twelve fractions of DOM samples using sequential solid phase extraction on nonionic sorbent at steadily lowered pH values: 7, 5, 3, 2, which correspond to low bounds of pKa values of phenols, aliphatic and aromatic carboxylic acids and ketoacids. The structural studies were conducted with a use of NMR and selective deuteromethylation of isolated fractions coupled to ultra-high resolution mass spectrometry. First, a gradual shift of molecular compositions was observed from reduced components to aromatic oxidized compounds isolated at pH7 and 2, respectively. Changes in molecular compositions were accompanied by a red shift of fluorescence spectra. Further application of deuteromethylation enabled to distinguish DOM constituents with different amount of carboxylic groups. Moreover, identification of structural isomers in a single DOM sample was achieved. Statistical analysis revealed that red shift of fluorescence is facilitated by the increase of a contribution of aromatic polycarboxylic acids with high conjugation lengths. Additionally, analysis of the labeled fractionated permafrost thaw DOM directly showed carboxyl-rich alicyclic molecules, while same components from lower-latitude DOM were assigned to lignin-like species.
关键词： DOM,structure,separation,acidity,fluorescence,SPE extraction,isotopic labeling,FTICR MS
更新于2025-09-19 17:13:59
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Fabrication of controllable wettability of crystalline silicon surfaces by laser surface texturing and silanization
摘要： This paper aims to explore the e?ects of laser surface texturing and chemical modi?cations by silanization on the wettability of silicon surfaces. To e?ectively prepare super-hydrophobic surfaces on silicon, a process using laser texturing with following silanization treatment is used to modify the surface. The surface wettability is evaluated by water contact angle (WCA). To ascertain the e?ect of laser texturing on wettability, the morphological and metallurgical modi?cations of the surface were investigated by scanning electron microscopy (SEM), white light confocal microscope and X-ray photoelectron spectroscopy (XPS). It is found that the fresh laser-processed silicon surface is super-hydrophilic, which is in line with the Wenzel model. A super-hydrophobic surface with a WCA > 150° was successfully obtained after silanization treatment. Silanization by a concentration of 0.72 wt% 1H, 1H, 2H, 2H-per?uorodecyltrichlorosilane with 2 h of immersion time was found to be the most e?ective condition for achieving super-hydrophobic silicon surfaces. The e?ects of acids, alkalis and salts on wettability have also been assessed. The results indicate that as-prepared silicon samples with a ?uoride coating can be normally used in acid condition but not suitable for use in alkaline and salty environments.
关键词： Laser texturing,Wettability,Silanization,Alkalinity,Silicon,Acidity,Salinity
更新于2025-09-16 10:30:52
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Highly efficient photocatalytic reduction of CO2 on surface-modified Ti-MCM-41 zeolite
摘要： Three dimensional microporous zeolites have attracted much attention in catalysis because of their large BET surface area and abundant pores. Herein, Ti-MCM-41 zeolites with different molar ratio of Si/Ti were synthesized, and the surface acidity and active sites were adjusted by the modification of basic-earth metal oxides, and noble metal nanoparticles. The photocatalytic activity and selectivity were evaluated by the reduction of CO2 to CH4 and CO. The results indicated that the efficiency and selectivity of CO2 photoreduction to CH4 of Ti-MCM-41 zeolites were 93 ppm·g-1·h-1 and 29% in the ratio Si/Ti=10 under keeping the zeolite structure, and which is much higher than that of P25 with the value of 24 ppm·g-1·h-1 and 23%. When the surface of Ti-MCM-41 zeolites was modified by different basic-earth metal oxides, the photo-reduction activity of CO2 to CH4 increased about 1.5 times with MgO modification, and the selectivity of CO2 to CH4 improved to 42%. Moreover, the photoactivity and selectivity enhanced to 8835 ppm·g-1·h-1 and 93% when the surface was further decorated by Pt nanoparticles, while the selectivity of CO2 to CO reached 94% when Pd was loaded. Our work reveal reasonably that adjusting the acidity and active site of the microporous zeolites is a highly efficient way to improve the photocatalytic efficiency of CO2 reduction.
关键词： Ti-MCM-41 zeolite,active sites,surface acidity,CO2 photoreduction
更新于2025-09-09 09:28:46
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Ga-SBA-3 A novel nanostructured material: synthesis, characterization and application
摘要： This paper reports for the first time the incorporation of gallium into the structure of the mesoporous SBA-3 material in order to modify the intrinsic acidity of the material. The nanostructured material was characterized by ICP, XRD, NMR-MAS, XPS, FTIR, SEM, TEM and UV Vis., Pyridine was used as a probe molecule for the determination of its acidity following the amount and type of acidic sites by FTIR. In addition, aniline adsorption/desorption studies and subsequent in-situ polymerization, PANI/Ga-SBA-3, were carried out with the aim of producing a nanocomposite with conductive properties. The original material had good structural regularity and acidity of Br?nsted and Lewis; the study indicates the effective incorporation of Ga into a network in tetrahedral form, with most in the interior of the lodging and a low proportion on the external surface. Gallium was introduced via post synthesis using Ga-Nitrate in appropriate conditions. The PANI/Ga-SBA-3 composite also showed a conductivity of 2.5x10-3 S/cm, higher than that of its homologs Al-SBA-3 and Al-MCM- 41.
关键词： Ga in tetrahedral form,PANI/Ga-SBA-3,Post synthesis incorporation,Br?nsted and Lewis acidity,Ga-SBA-3,conductive nanocomposite
更新于2025-09-09 09:28:46
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TiO <sub/>2</sub> /zeolite Bifunctional (Photo)catalysts for a Selective Conversion of Methanol to Dimethoxymethane: On the Role of Br?nsted Acidity
摘要： In the present work, we report the first example of one-step selective methanol photooxidation to dimethoxymethane (DMM) at room temperature over TiO2/zeolite bifunctional catalysts. The effects of the porosity, basicity/acidity of the zeolites on the selectivity of the reaction are discussed. The role of TiO2 active sites and zeolitic Br?nsted acid sites on the DMM production is reported. As the photocatalytic reaction occurs at room temperature, the influence of the reaction temperature is also investigated to extrapolate the results to thermal catalysis. This study demonstrates a clear synergetic effect of the zeolites on the selectivity of the reaction. They can display an important impact on the selectivity of the photocatalytic reaction even at a low temperature (e.g. room temperature). Based on the obtained results, the reaction mechanism of methanol conversion to DMM is elucidated.
关键词： Br?nsted acidity,dimethoxymethane (DMM),selective conversion,methanol photooxidation,TiO2/zeolite bifunctional catalysts
更新于2025-09-09 09:28:46
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Perylene-Based Fluorescent Nanoprobe for Acid-Enhanced Detection of Formaldehyde in Lysosome
摘要： Formaldehyde (FA), as a reactive carbonyl species, is extremely hazardous to human health if its concentration is above normal level. In live cells, lysosome is a main organelle to generate endogenous FA. Thus, the design of facile, stable and sensitive probes for the detection of FA in lysosome is essential. Herein, a self-assembled fluorescent nanoprobe based on homoallylamino substituted perylene (P-FA) has been developed for FA detection in lysosome. P-FA can react with FA along with emission color change from blue to green. P-FA exhibited high sensitivity and selectivity to FA in DMSO solution. In aqueous solution, P-FA self-assembled into uniform sphere-like nanoparticle as a fluorescent nanoprobe. Furthermore, the reaction between the nanoprobe and FA was greatly facilitated at pH 4-5, leading to a lower detection limit (0.96 μM at pH 5) than that in DMSO. In live cells, P-FA nanoprobe achieved long-term tracking of lysosome (over 12 h). The fluorescent nanoprobe was then used for both exogenous and endogenous FA detection. Our work provides a facile and effective strategy for the detection of FA in lysosome.
关键词： Weak Acidity,Perylene,Formaldehyde Detection,Lysosome,Fluorescent Nanoprobe
更新于2025-09-04 15:30:14