Carbonyl Bond Research Articles

Theoretical insights into the spectroscopic properties of ferrocenyl hetaryl ketones

Quantum chemical calculations have been carried out to elucidate the electronic structure as well as to draw structure-property relationships for a series of ferrocenyl hetaryl ketones by means of simulated NMR, IR and UV–vis spectra. In this series, the list of hetaryl groups included furan-2-yl, thiophen-2-yl, selenophen-2-yl, 1H-pyrrol-2-yl and N-methylpyrrol-2-yl. Density functional theory was employed to determine the ground-state properties of the five ketones while their excited-state properties were modeled using a broad range of theoretical methods, namely from time-dependent density functional theory to multiconfigurational and multireference ab initio approaches. The patterns in the 13C and 17O chemical shifts of the carbonyl group were explained by the geometrical twist of hetaryl rings and by the electronic parameters corresponding to π-bonds conjugation and group hardness. Furthermore, the corresponding 13C and 17O shielding constants were analyzed in terms of both their dia/paramagnetic and Lewis/non-Lewis contributions within the framework of natural chemical shielding theory. The pattern in the vibrational frequency of the carbonyl bond was connected with changes in its bond length and bond order. It was established that the electronic absorption spectra of the studied ketones are largely characterized by low-intensity d → π* transitions in the visible region and the dominant high-intensity π → π* transition in the UV region. Finally, the theoretical methods best suited for modeling the excited-state properties of such ketones were designated.

Green electrolyte host based on synthesized benzoyl kappa-carrageenan: Reduced hydrophilicity and improved conductivity

Newly synthesized benzoyl kappa carrageenan (Bz-ƙcar) was successfully produced by the Friedel Craft acylation method. The successful substitution of benzoyl molecule into kappa carrageenan (ƙcar) polymeric chain was confirmed by the FTIR analysis based on the formation of new carbonyl (CO) and CC bonds in Bz-ƙcar. 1H NMR analysis further proved the benzoylation by the appearance of new multiple resonances peaks at δ = 6.6–9.50 ppm, which belonged to the characteristic signals of protons in the aromatic benzoate group. XRD analysis showed reduced crystallinity of the synthesised carrageenan, while elemental analyser analysis revealed the increased percentages of carbon in Bz-ƙcar upon the substitution. The highest degree of substitution obtained was 0.27. TGA showed lower degradation temperature in the synthesised carrageenan, while water contact angle analysis demonstrated that Bz-ƙcar was less hydrophilic as compared to the pristine ƙcar. Solubility tests showed that Bz-ƙcar was best dissolved in ethylene glycol. The benzoylation also improved the ionic conductivity of Bz-ƙcar to 3.10 × 10−4 Scm−1 at ambient temperature.

Construction of macromolecular model and analysis of oxygen absorption characteristics of Hongyang No. 2 coal mine

Understanding the molecular structure characteristics of coal from the molecular level is of great significance for realizing rational utilization and efficient transformation of coal. The molecular structure of coal samples from 1304 working face in No.13 coal seam of Hongyang No.2 Mine (HY) was studied by industrial analysis, elemental analysis, Nuclear magnetic resonance carbon spectroscopy (13C NMR) and Fourier transform infrared spectroscopy (FTIR). The results show that the aromatic compounds in coal samples of HY are mainly naphthalene ring structures. The aliphatic structure mainly consists of methyl, ethyl side chains and cycloalkanes. The ratio of aromatic bridge carbon to weekly carbon in molecular structure is 0.17. Oxygen atoms exist in the form of carbonyl, hydroxyl, and ether bonds, nitrogen atoms exist in the form of pyridine and pyrrole respectively, and sulfur atoms exist in the form of thiophene. Based on this, the planar structure model of coal macromolecule in HY is constructed, and its molecular formula is C129H88O29N2S, and its molecular weight is 2160. The structure optimization and annealing kinetics simulation of a single macromolecule model were carried out, and a stable three-dimensional coal model of HY was obtained. In addition, the oxygen absorption characteristics of coal samples in HY were studied by molecular dynamics and quantum chemistry. The results show that the adsorption capacity of the Wiser model is less than that of HY coal model. This is because, compared with the Wiser model, the content of oxygenated aliphatic hydrocarbons in the molecular structure of HY coal is higher, and the condensation degree of polycyclic aromatic hydrocarbons is lower. Due to the stronger physical adsorption capacity of hydroxyl, ether bond, and carbonyl on O2, HY Mine has stronger physical adsorption capacity on O2.

Manipulating active sites on carbon nanotube materials for highly efficient hydrogen storage

The active sites in porous carbon nanotube (CNT) would determine hydrogen storage performance of CNT. Here, we reported an effective, simple and controllable strategy to improve the hydrogen storage property of function group grafted CNT (fg-CNT). N-CNT-M (La2O3, Ni) would be obtained by the mixture of fg-N-CNT and metallic precursor at calcination of 600 °C. N-CNT-La2O3 has the highest H2 storage capacity of 7.4 wt%, displaying stable hydrogen adsorption/ desorption cycles for more than 20 times at 100 °C and 18 bar. fg-Ni-CNT-PLLA were formed by electrostatic interactions between CN bond of amide and carbonyl of l-polylactic acid (PLLA). fg- Ni-CNT-PLLA also has H2 storage capacity of 6.2 wt% at 100 °C and 18 bar. The experiment found that metal ions or PLLA might be dispersed uniformly in CNT by adjusting the ratio of grafted hydroxyl (OH) to acylamino (–CONH2). N-CNT-La2O3 has better hydrogen storage performance than fg-CNT-PLLA because the aggregation of CNT would be caused by the molecular movement of PLLA during hydrogenation and dehydrogenation. This work provides guidance for the development of efficient hydrogen storage materials.

Nanofibrous hybrid scaffolds based on PCL-borosilicate system by a green sol-gel process

Tissue regeneration is yet a critical issue, and to mimic the natural extracellular matrix (ECM) innovative scaffolds need to be developed to ensure the functional and safe repair of the damaged organs or tissues. Hybrid biomaterials based on the combination of a biodegradable polymer and bioactive glasses (BGs) are potential candidates for tissue engineering (TE), since they exhibit tailored physical, biological, and mechanical properties, as well as controlled degradation behavior. Thus, the main purpose of this research was to develop by electrospinning (ES) a hybrid nanofibrous membrane composed of a synthetic polymeric matrix (PCL) and a boron and calcium silicate glass, formed via in situ sol-gel, and based on a non-aqueous and green fabrication route. Formic acid (FA) and glacial acetic acid (AA) were used as green solvents to dissolve the PCL. Different compositions were prepared: neat PCL and PCL/SiO2–B2O3–CaO with different sol-gel aging times and green solvent systems. All prepared hybrid solutions, except the composition with only AA, were spinnable. Structural features of the hybrids were assessed by ATR-FTIR spectroscopy, which confirmed the presence of siloxane (Si–O–Si) bonds of silica and carbonyl (CO) bonds characteristic of PCL polymer as well as intermolecular hydrogen-bonding interactions between the carbonyls of PCL and the silanol hydroxyls (Si–OH) of silica networks. Boron (B–O–B) and borosiloxane (B–O–Si) bonds were not visible due to the overlapping of PCL bands in the spectra. Only the solid state 11B NMR technique allowed to find peaks assigned to trigonal BO3 and tetrahedral BO4 groups, which evidence the boron linkages to silica. Thermal analysis showed a change in the crystallinity of PCL with the incorporation of inorganic domains, confirming the formation of chemical interactions between the polymer and the inorganic part. Microstructure and chemical analysis, by SEM/EDS, showed a homogenous distribution of Ca and Si elements into the fibers, as well as an increase of the fiber diameter with the incorporation of boron and calcium silicate glass in the PCL. The developed compositions of PCL/boron and calcium-containing silicate were feasible to electrospin into fibrous meshes, proving its potential for further design of multicomponent nanofibrous microstructures closer to extra cellular matrix architectures.

Carbon-deuterium bonds as reporters of electric fields in solvent and protein environments.

Use of vibrational probes to measure electric fields inside proteins has illuminated the role of electrostatics in biological applications ranging from binding interactions to enzyme catalysis. While prior work focused on strongly absorbing carbonyl and nitrile probes, more recent work has begun exploring weakly absorbing carbon-hydrogen bonds, beginning with measurements of electric fields inside oxidoreductases using the vibrational Stark effect (VSE). Originally, an alcohol dehydrogenase inhibitor containing a deuterated aldehyde was used to measure the field in two directions—on carbonyl and carbon-deuterium (C-D) bonds—in the enzyme active site. Now, several more distinct cases demonstrate how C-D probes map electric fields to vibrational frequency shifts, with new implications for our understanding of the VSE. To probe the field along a different dimension in oxidoreductases, we consider singly deuterated NAD(P)H which reports fields along the hydride transfer axis and whose frequency detection is facilitated by advancements in quantum cascade laser (QCL) technology for infrared spectroscopy. Unusually, the solvatochromic shift for this C-D probe appears opposite to that observed for carbonyls and nitriles; that is, the probe blueshifts in more polar solvents. In another example, the chromophore of green fluorescent protein (GFP) with a deuterated bridge carbon demonstrates similarly unusual frequency shifts in solvent and protein environments, with stronger fields parallel to the C-D dipole causing blueshifts. Observed Stark tuning rates for these molecules are recapitulated by in silico Stark calculations at the B3LYP or ωB97X-D/6-31+G(d) level. Stark tuning rate comparison with other C-D containing molecules including deuterated aldehydes and chloroform-d indicates a large sensitivity of the Stark tuning rate to molecular structure. We demonstrate how properly calibrated C-D probes can be effective reporters of electric fields in applications such as enzyme-catalyzed hydride transfer, biological photophysics and beyond.

Carbon template synthesis of CeO2 catalyst for direct conversion of methanol and carbon dioxide to dimethyl carbonate

Dimethyl carbonate (DMC) is an interesting, value added chemical and a high energy additive to fuels. In this study, several CeO2 catalysts were successfully synthesized through carbon template method using two renewable sources of activated carbon. The structure of catalysts was fully resolved by XRD, SEM, N2-adsorption, NH3-TPD, CO2-TPD and XPS. CeO2 catalysts prepared using coconut shell activated carbon (CAC) template exhibit better surface morphology and improved catalytic performance compared to walnut shell activated carbon (WAC)-supported catalysts. We demonstrated a correlation between the efficiency of DMC synthesis and the abundance of moderately acidic and moderately basic active sites on the catalyst. It was found that the presence of oxygen vacancies (Vo) facilitates carbonyl bond cleavage of CO2. The best-performing catalyst was 4% CeO2/CAC owing to the richest Vo and the optimum acid/base properties. Moreover, a plausible catalytic mechanism of DMC formation was proposed, and includes the interaction between methoxy carbonate (CH3OCO2−) formed with the aid of Vo and moderately basic sites and methyl cation (CH3+) formed on the moderately acidic sites.

PREPARATION AND CHARACTERIZATION OF ACTIVATED CHARCOAL FROM BAMBOO WASTE WITH PHOSPHORIC ACID AS A BIOSORBENT FOR RHEMAZOL BRILLIANT BLUE

Bamboo waste can be converted into materials of high economic value when processed into activated charcoal which is useful as an adsorbent. This study aims to make activated charcoal from bamboo waste with 20%(w/v) phosphoric acid as an activator. The activated charcoal produced was used as an adsorbent for rhemazol brilliant blue dye. Characterization of activated and inactivated charcoal was carried out by referring to the Indonesian National Standard-1995. Contact time and pH were studied for optimizing the adsorption. The results showed that the optimum contact time was 60 minutes, and the pH of the solution was 2. Isotherm adsorption of both charcoals tends to follow Langmuir isotherm, and the adsorption capacity obtained was 12.2399 and 9.5697 mg/g for activated and nonactivated charcoals respectively. Adsorption kinetic charcoals follow to pseudo-second order. Both charcoals are thought to contain functional groups of hydroxy, carbonyl, and aliphatic double bonds and have heterogeneous surfaces.

Revealing the mechanism of damage to the carbonate ester in PADC polymeric nuclear track detector using low-energy electron stimulated desorption.

We investigate the mechanism of damage to the carbonate ester chemical functions in Poly allyl diglycol carbonate (PADC) induced by low-energy electrons (LEEs) of <50 eV, which are major components of the initial secondary products of ionizing radiation. PADC is the world's most widely used polymeric nuclear track detector (PNTD) for swift ion detection. Using diethylene glycol monoethyl ether acetate as a surrogate for PADC, we have measured for irradiation with low-energy electrons (LEEs) of <50 eV, the electron stimulated desorption (ESD) signal of O- from 3-monolayer thick films of DGMEA by time-of-flight mass spectrometry. We find that for electron irradiation at energies >6-9 eV, the instantaneous ESD yield of O- increases with the cumulative number of incident electrons (i.e., fluence), indicating that the additional O- signal derives from an electron-induced DGMEA product. From comparison with ESD measurements from films of acetic acid and acetaldehyde, we identify that the additional desorbed O- signal derives from oxygen atoms originally adjacent to the carbonyl bond in DGMEA. Since LEEs are the predominant secondary particles produced by ionizing radiation, this finding helps to better understand the mechanism of damage to carbonate ester in PADC, which is a key step for latent track formation in PADC.

Chitosan-based 2D highly conductive porous carbon nanosheet as supercapacitor electrode with high voltage and long lifespan

With the expanding application of supercapacitors, the industry puts forward higher demand for the energy density ( E ) of supercapacitors. Normally, increasing voltage is more effective means to improve E . However, it is challenging to construct porous carbons that can withstand ultra-high voltage in organic electrolyte. In this study, 2D highly conductive porous carbon nanosheet (CPCN) with uniform thickness of 20 nm is synthesized by the hydrothermal crosslinking, activation and annealing methods from chitosan biomass. The CPCN exhibits reasonable specific surface area of 2199 m 2 g −1 . The CPCN consists of abundant short-range ordered graphite microcrystals with nitrogen-doping content of 1.61 wt% and high sp 2 carbon (88.7 %), thereby contributing to the electrical conductivity as high as 108 S m −1 . Moreover, the CPCN owns low oxygen content of 4.79 wt%, in which the stable carbonyl and ether bonds dominate. Thus the withstanding voltage of CPCN can be up to 3.2 V in TEABF 4 /PC electrolyte. It delivers good specific capacitance of 114.0 F g −1 at 1 A g −1 with rate performance of 78.1 %. And the E can reach 41.9 Wh kg −1 . Significantly, CPCN can own ultralong lifespan of 84.2 % after 50,000 cycles at 2.5 A g −1 . • 2D highly conductive porous carbon nanosheet is constructed from chitosan. • It has ultrathin thickness and high e -conductivity. • The very-low oxygen content guarantees high tolerance towards ultrahigh voltage. • The voltage can be raised up to 3.2 V in TEABF 4 /PC electrolyte. • High energy density up to 41.9 Wh kg −1 and superior lifespan are achieved.

The influence mechanism of lignite thermal upgrading on moisture re-adsorption

The influence mechanism of lignite thermal upgrading on moisture re-adsorption was investigated using analytical techniques such as differential thermal analysis–thermogravimetry, Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that the moisture content of lignite decreased from 44.78 to 25.07% through the drying process. After the moisture in the lignite and the air had reached a dynamic equilibrium, the moisture content of the lignite was 25.75 wt.%. The characteristic functional groups of lignite include hydroxyl, methylene, methyl, carbonyl, carboxyl and ether oxygen. The adsorption distances of the five adsorption sites of carboxyl, phenolic hydroxyl, alcoholic hydroxyl, carbonyl and ether bond to water molecules were 2.081, 2.933, 1.905, 1.860 and 1.881 Å, respectively. The order of the adsorption strength of water molecules on the characteristic functional groups was carbonyl &gt; phenolic hydroxyl &gt; ether oxygen &gt; alcoholic hydroxyl &gt; carboxyl. During the upgrading by drying process, the characteristic functional groups that were prone to hydrogen bonds of water molecules partially decomposed. The reduction of pores and the partial decomposition of hydrophilic functional groups after upgrading in the lignite structure weakened the adsorption capacity of lignite to water molecules. Therefore, the re-absorption of water molecules by lignite was reduced.

A new Raman spectroscopy‐based method for monitoring the crystallinity ratio of polyethylene terephthalate

AbstractTracking the Raman scattering bands of polyethylene terephthalate (PET) during thermal heating has allowed to establish criteria for monitoring the crystallinity ratio within a few seconds. The existing criteria, based on Raman bands at 998 cm−1 and at 1096 cm−1, present certain disparities from the crystallinity ratio given by the total heat flow in differential scanning calorimetry (DSC). Based on the evolution of the Raman bands, a newfound method allowing the effective calculation of crystallinity ratio is proposed. For the same, the band at 1727 cm−1, which is characteristic of the C=O carbonyl bonds of the ester group of PET, is used. The new criterion, designated r1727,2, was compared and validated by DSC and XRD. This novel approach also provides access to information on the various conformational states of the bonds under study, that is, their proportions and positions with respect to the plane of the macromolecule aromatic rings. Evidently, this allows to reveal the characteristic thermal behavior of the PET microstructure such as the glass transition, crystallization, and melting. This method can be useful for the close detection, quantification, understanding, and tracing of the micromechanisms involved at the macromolecular conformations scale during thermal cycles.

Development of iron-vitamin multilayer encapsulates using 3 fluid nozzle spray drying

Considering the growing concern of iron and folic acid deficiency, encapsulation of these nutrients and fortification into foods is emerging as an effective counter-strategy. The present work focuses on a scalable approach for the production of iron, ascorbic acid, and folic acid core–shell encapsulates using novel 3-fluid nozzle (3FN) spray drying with whey protein as core and either pectin or hydroxypropyl methylcellulose (HPMC) as shell polymers. The effect of shell formation was observed by comparing core–shell encapsulates with conventional 2-fluid nozzle (2FN) encapsulates. Also, the effect of pH of whey protein on the color of encapsulates is noteworthy; reducing the pH to 4.0 significantly improved the lightness value (52.91 ± 0.13) when compared with the encapsulates with native pH (38.91 ± 0.58). Furthermore, sample with pectin as shell polymer exhibited fair flowability with lowest values of Hausner ratio (1.25 ± 0.04) and Carr’s index (20.06 ± 2.71) and highest encapsulation efficiency for folic acid (86.07 ± 5.24%). Whereas, encapsulates having HPMC as shell polymer showed highest lightness value (60.80 ± 0.32) and highest encapsulation efficiency for iron (87.28 ± 4.15%). The formation of core–shell structure was confirmed by evaluation of the surface composition which showed reduced amine bonds and increased aliphatic and carbonyl bonds in the encapsulates prepared by 3FN spray drying. The encapsulates prepared without adjusting whey protein pH showed the least release (∼51 % in 24 h) and bioaccessibility (∼56%) of iron indicating the iron-whey protein complex formation. Based on appearance, smooth surface morphology, flowability, and release behavior, a combination of whey protein and pectin is recommended for co-encapsulation of iron, folic acid and ascorbic acid.

Two-dimensional titanium carbide (MXene)-supported Pt3Ti intermetallic compound catalysts for efficient room-temperature oxidative removal of gaseous formaldehyde

The potential of reactive metal–support interactions has been investigated using platinum (Pt) and a two-dimensional titanium carbide (Ti3C2 [MXene]) support to achieve the full conversion of formaldehyde (FA: XFA) into carbon dioxide (CO2) at room temperature (RT) through the formation of a Pt3Ti intermetallic compound. The RT steady-state oxidation reaction rate (mol/g/h) of FA increased in the following order: 2% Pt/Ti3C2 (0.020) < 0.1% Pt/Ti3C2-R (0.054) < 1% Pt/Ti3C2-R (0.058) < 2% Pt/Ti3C2-R (0.061: turnover frequency of approximately 60 mmolFA/molO/s). The Pt3Ti formed in situ during reduction pre-treatment (R) enhanced catalytic activity, and 2% Pt/Ti3C2-R achieved significant resistance to moisture by maintaining 100% XFA at a relative humidity of 0%–90%. In situ diffuse reflectance infrared Fourier-transform spectroscopy revealed the formation of dioxymethylene, formate, and carbon monoxide as the reaction intermediates of FA oxidation. According to the density functional theory simulations, the carbonyl bond (C=O) of FA appears to be activated through chemisorption on Pt3Ti (adsorption of oxygen and carbon atoms (in C=O) on the Pt and titanium sites of Pt3Ti, respectively) to generate CO2 through reaction with active oxygen species formed by the decomposition of molecular oxygen on the Pt/Ti sites. In terms of the normalized reaction rate, 0.1 Pt/Ti3C2-R (0.55 mol/g/h [bulk Pt, wt.%]–1) appears to be one of the best-performing Pt catalysts reported for FA oxidation at RT.

Direct wiring of redox cofactors onto gold electrodes via inorganic iron-sulfur clusters enhances charge transport

Inorganic iron-sulfur clusters (Fe–S) have emerged as potential electrode anchors and electron shuttles for enzymatic biosensor systems involving nicotinamide adenine dinucleotide (NAD) cofactor. In this work, we report how other cofactors that include nicotinamide adenine dinucleotide phosphate (NADP), flavin adenine dinucleotide (FAD), pyrroloquinoline quinone (PQQ), and coenzyme-Q10 (CoQ10), electrochemically respond to iron-sulfur mediated gold electrodes. Here, select redox cofactors were tethered onto gold electrode supports via inorganic Fe–S (FeS, FeS2, Fe2S3, Fe3S4) and organic Fe–S (Ferredoxin), using the layer-by-layer self-assembly. A combination of docking simulations, secondary ion mass spectrometry, and Fourier-transform infrared spectroscopy revealed the formation of iron carbonyl bonds between FeS and NAD, leading to electrochemical interactions between Fe–S and the redox cofactors. Electrochemical studies confirmed both inorganic and organic iron-sulfur molecules can anchor cofactors onto the gold electrode supports. Up to a 300% increase in anodic peak currents was observed when the inorganic Fe–S replaced the organic counterpart, Ferredoxin, to wire the cofactors onto the gold electrodes. Electrode kinetic measurements revealed the reversible and quasi-reversible behavior of the inorganic and organic Fe–S electrodes, respectively. Reductive desorption studies indicated Fe3S4 closely followed by FeS, forming robust wiring associations with gold by displaying the highest surface coverage, desorption power, and the lowest resistance. Consequently, the inorganic iron-sulfur clusters facilitate an effective method for fabricating enzymatic biosensors for many analytes based on the enzyme-cofactor combination.

Predicting the Anticancer Activity of 2-alkoxycarbonylallyl Esters against MDA-MB-231 Breast Cancer - QSAR, Machine Learning and Molecular Docking.

The continuous increase in mortality of breast cancer and other forms of cancer due to the failure of current drugs, resistance, and associated side effects calls for the development of novel and potent drug candidates. In this study, we used the QSAR and extreme learning machine models in predicting the bioactivities of some 2-alkoxycarbonylallyl esters as potential drug candidates against MDA-MB-231 breast cancer. The lead candidates were docked at the active site of a carbonic anhydrase target. The QSAR model of choice satisfied the recommended values and was statistically significant. The R2pred (0.6572) was credence to the predictability of the model. The extreme learning machine ELM-Sig model showed excellent performance superiority over other models against MDAMB- 231 breast cancer. Compound 22 with a docking score of 4.67 kcal mol-1 displayed better inhibition of the carbonic anhydrase protein, interacting through its carbonyl bonds. The extreme learning machine's ELM-Sig model showed excellent performance superiority over other models and should be exploited in the search for novel anticancer drugs.

Ligand-Assisted Carbonyl Bond Activation in Single Diastereomeric Complexes on Platinum

Ligand-Assisted Carbonyl Bond Activation in Single Diastereomeric Complexes on Platinum

Facile synthesis of red-emissive carbon dots with theoretical understanding for cellular imaging

Recently, red emissive carbon dots (R-CDs) have drawn widespread attention on account of their desirable fluorescence properties and good biocompatibility. Despite great efforts, facile synthesis of R-CDs for cellular imaging remains challenging and the fluorescence mechanism of R-CDs is still elusive. Herein, p-phenylenediamine-derived R-CDs with excitation-independency were successfully obtained through a facile solvothermal approach together with proportional precipitation. The fluorescent solvatochromism of R-CDs is realized, while high polarity leads to higher degree of dipole interaction between R-CDs and different solvents, favoring for emissive red-shift. Furthermore, density functional theory is adopted to explore the optical and electronic characteristics of some polycyclic aromatic molecules. Among different configurations, pyridine nitrogen and carbonyl bonds could relatively increase the charge density and significantly narrow the band gap, which can provide a crucial theoretical basis for the precise preparation of R-CDs. Moreover, R-CDs possess favorable cellular imaging ability, which indicates their potential for a promising candidate as fluorescence probes in bioimaging.

Isothermal crystallization of polyhydroxyalkanoate (PHA) utilizing Raman spectroscopy to follow chain packing as well as molecular motion

Raman spectra of bioplastic poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx at 13.8 % Hx) were recorded between −250 cm−1 and 3200 cm−1 during isothermal crystallization at 25⁰C after quenching from the melt in liquid nitrogen. At room temperature the crystallization proceeds slowly, so spectra were recorded over a 14-hour period. While there are spectral changes throughout the spectrum, the focus was on interpretable bands known to be sensitive to crystalline form. These bands included the carbonyl band that sharpens and shifts, a pair of bands on the high energy side of the carbon-hydrogen stretch, and a low frequency band that we assign to the molecular phonon in the crystal unit cell. After appropriate pre-processing of the spectra, they were further analyzed by 2D-COS (two-dimensional correlation spectroscopy) that provides determination of the order in which the polymer functional regions assemble into the crystalline state. According to this analysis one of the methyl CH’s interacts with the carbonyl bond to produce a line at 3000 cm−1. Following that, multiple changes appear in the carbonyl region, the strong CH band at 2930 cm−1 of the crystalline phase grows, then the 80 cm−1 phonon band, and the splitting of the methyl CH only appears after the phonon. From this sequence one can derive a picture of how the polymer unit locks into the crystal form. This can be of interest to commercialization of the materials because mechanical properties are intimately controlled by the crystallinity of the material. By understanding how the crystallization process proceeds, it can be engineered to be “fit for purpose” for a polymer targeted for a specific use.

Biocontrol potential of mycogenic copper oxide nanoparticles against Alternaria brassicae.

The biological synthesis of nanoparticles using fungal cultures is a promising and novel tool in nano-biotechnology. The potential culture of Trichoderma asperellum (T. asperellum) has been used to synthesize copper oxide nanoparticles (CuO NPs) in the current study. The necrotrophic infection in Brassica species is caused due to a foliar pathogen Alternaria brassicae (A. brassicae). Mycogenic copper oxide nanoparticles (M-CuO NPs) were characterized by spectroscopic and microscopic techniques such as UV–visible spectrophotometry (UV–vis), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The antifungal potential of CuO NPs was studied against A. brassicae. M-CuO NPs exhibited a surface plasmon resonance (SPR) at 303 nm, and XRD confirmed the crystalline phase of NPs. FTIR spectra confirmed the stretching of amide bonds, and the carbonyl bond indicated the presence of enzymes in T. asperellum filtrate. SEM and TEM confirmed the spherical shape of M-CuO NPs with an average size of 22 nm. Significant antifungal potential of M-CuO NPs was recorded, as it inhibited the growth of A. brassicae up to 92.9% and 80.3% in supplemented media with C-CuO NPs at 200 ppm dose. Mancozeb and propiconazole inhibited the radial growth up to 38.7% and 44.2%. SEM confirmed the morphological changes in hyphae and affected the sporulation pattern. TEM revealed hardly recognizable organelles, abnormal cytoplasmic distribution, and increased vacuolization, and light microscopy confirmed the conidia with reduced diameter and fewer septa after treatment with both types of NPs. Thus, M-CuO NPs served as a promising alternative to fungicides.