Amide Functional Groups Research Articles

Synthesis, structural characterization, and anion binding studies of bisamide functionalized molecular clefts

The utilization of amide functional groups as anion-binding sites in the structure of synthetic anion receptors has received significant attention. In this study, three new compounds, namely, N,N′-bis(2-(pyridin-2-yl)ethyl)pyridine-2,6-dicarboxamide (L1), N,N′-bis(2-(pyridin-3-yl)ethyl)pyridine-2,6-dicarboxamide (L2), and N,N′-bis(2-(pyridin-4-yl)ethyl)pyridine-2,6-dicarboxamide (L3), have been successfully synthesized. These compounds were fully characterized using a combination of spectroscopic techniques such as Fourier transform infrared spectroscopy, gas chromatography–mass spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy, elemental analysis, and ultraviolet–visible (UV–Vis) spectroscopy. Further investigation on the potential of these compounds to bind with anions, such as chloride, nitrate, chromate, and phosphate, has been conducted using UV–Vis titration and a fluorescence titration method, and the results revealed that compound L2 has high potential to bind with chloride, chromate, and phosphate anions compared with other investigated hosts and analytes. This has opened a good opportunity for further application bisamide compound as anion sensing materials in the future.

A library of benzimidazole based amide and urea derivatives as supramolecular gelators – A comparative study

We present a set of alkyl chain functionalized benzimidazole based compounds containing amide and urea functional groups which were screened for their gelation behaviour. Both the sets bear similar molecular scaffolds, making them an excellent tool for determining the role of the supramolecular interactions involved in the gelation process. All the compounds were characterised using physico-chemical techniques like NMR and FT-IR. The gels were subjected to small angle neutron scattering studies (SANS), rheological studies, SEM and FT-IR. In order to rationalize the gelation behaviour, solvent parameter studies were conducted. The results show a dependence on refractive index of solvent, polarizability and dispersion interactions. The respective orientation of amide and conformation in urea based compounds were explored and studied using computational calculations and their corresponding effect on the resulting supramolecular superstructures was scrutinized. The compounds were also explored to act as chemosensor for selective detection of mercuric ions with exceptionally low LOD (limit of detection) values.

Efficient recycling pathway of bio-based composite polyurethane foams via sustainable diamine

Aminolysis is widely recognized as a valuable chemical route for depolymerizing polymeric materials containing ester, amide, or urethane functional groups, including polyurethane foams. Bio-based polyurethane foams, pristine and reinforced with 40 wt% of sustainable fillers, were depolymerized in the presence of bio-derived butane-1,4-diamine, BDA. A process comparison was made using fossil-derived ethane-1,2-diamine, EDA, by varying amine/polyurethane ratio (F/A, 1:1 and 1:0.6). The obtained depolymerized systems were analyzed by FTIR and NMR characterizations to understand the effect of both diamines on the degradation pathway. The use of bio-based BDA seemed to be more effective with respect to conventional EDA, owing to its stronger basicity (and thus higher nucleophilicity), corresponding to faster depolymerization rates. BDA-based depolymerized systems were then employed to prepare second-generation bio-based composite polyurethane foams by partial replacement of isocyanate components (20 wt%). The morphological, mechanical, and thermal conductivity properties of the second-generation polyurethane foams were evaluated. The best performances (σ10 %=71 ± 9 kPa, λ = 0.042 ± 0.015 W∙ m-1 ∙K-1) were attained by employing the lowest F/A ratio (1:0.6); this demonstrates their potential application in different sectors such as packaging or construction, fulfilling the paradigm of the circular economy.

Abstract A027: A photoactivatable microtubule-targeting rigidin prodrug

Abstract Analogues of marine alkaloid rigidins have been found to kill cancer cells at nanomolar concentrations by targeting the microtubule network. Here, a rigidin analogue containing a thioether group was “caged” by coordination of its thioether group to a photosensitive ruthenium polypyridyl complex. In the dark, the coordinated ruthenium fragment prevented the rigidin analogue from inhibiting tubulin polymerization and reduced its toxicity in 2D cancer cell lines monolayers, 3D lung cancer tumor spheroids (A549), and in a lung cancer tumor xenograft (A549) in nude mice. Photochemical activation of the prodrug upon green light irradiation led to the photosubstitution of the thioether ligand by water, thereby releasing the free rigidin analogue capable of inhibiting the polymerization of tubulin. In cancer cells, such photorelease was accompanied by a drastic reduction of cell growth, not only when the cells were grown in normoxia (21% O2) but also, remarkably, in hypoxic conditions (1% O2). In vivo, light activation of the compound in the tumor led to 30% tumor volume reduction, which represents the first demonstration of the efficacy of a ruthenium-based photocaged compounds in a tumor xenograft. In subsequent unpublished work, we fine-tuned the excited states in this complex by adding an amide functional group on the ruthenium cage. By doing so, a new caged complex was obtained that was activated by red light (instead of green light). We demonstrated the red light activation of this compound in solution and in vitro. This result demonstrates that functionalization of ruthenium cage with electron-withdrawing groups can radically enhance their photochemical properties, which is essential for this method development (red light penetrates better into tissues than green light). We will present our results of in vivo testing of this caged compound activated by tumor penetrable red light, where significant tumor reduction is seen in mice xenografted with subcutaneous human uveal melanoma liver metastatic cells. Citation Format: Alexander Kornienko, Sylvestre Bonnet. A photoactivatable microtubule-targeting rigidin prodrug [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A027.

Sorption and diffusion of per-polyfluoroalkyl substances (PFAS) in high-density polyethylene geomembranes

The objective of this study is to investigate the fate and transport of per-polyfluoroalkyl substances (PFAS) through a high-density polyethylene (HDPE) geomembrane (GM) that is commonly used in landfill composite liner systems. Tests were conducted to measure the sorption and diffusion of per-polyfluoroalkyl substances (PFAS) with varying number of carbons in chain and functional groups on HDPE GM. Perfluoroalkyl carboxyl acids (PFCAs), perfluoroalkyl sulphonic acids (PFSAs), alkyl-sulfonamidoacetic acids (FOSAAs), fluorotelomer sulfonic acids (FtSAs), alkane sulfonamides (FOSA) and ether carboxylic acids (Gen X) were investigated in this study. The partition coefficients (Kd) on HDPE GM ranged from 3.8 to 98.3 L/kg. PFAS with amide and sulfonic functional groups showed stronger sorption than that of PFAS with carboxylic acid functional groups. Molecular weight directly affected the Kd for long-chained PFAS whereas the Kd of short-chained PFAS was not sensitive to molecular weight. The diffusion coefficients (Dg) of PFCAs and PFSAs through 0.1-mm HDPE GM were found to be in the orders of 10-18 to 10-17 m2/s. The Dg decreased with increasing molar mass and were also observed to be dependent on the functional group. Dg of PFSAs was lower than that of PFCAs for similar number of carbons in the chain. The estimated mass flux for PFAS in an intact 1.5-mm HDPE GM varied from 38.7 to 2080.8 ng/m2/year whereas the estimated diffusive breakthrough time for PFAS in intact 1.5-mm HDPE was 1526 years or longer.

Michael addition reaction and its examples

Michael addition reaction refers to the conjugate addition reaction of carbocation to , -unsaturated aldehydes, ketones, carboxylic acids, esters, nitrile, nitro compounds, etc. The reaction is an essential organic reaction, and it is used in organic synthesis to grow carbon chains and synthesize organic compounds with various functional groups. As one of the most valuable organic synthesis reactions, it is one of the most common ways to construct carbon-carbon bonds. This paper analyzes the mechanisms and the theories of some common Michael addition reactions. It also includes an example of the research of Michael addition in recent years. In a recent study, a research team experimentally found a suitable catalyst to catalyze the Michael addition reaction on benzyl groups, and obtained the different performances of benzyl groups with different functional groups during addition. Cyclopentadienyl rhodium catalyst has excellent catalytic activity and selectivity for benzyl first, second, and third C/H bonds. The reaction can be compatible with halogen, ester, and amide functional groups.

Reactivity Umpolung of Amides in Organic Synthesis

AbstractAmides are important carboxylic acid derivatives, having wide applications in chemistry, biochemistry, and material science. Due to the conjugation (nN‐π*C=O), the carbonyl group of amides is the least electrophilic and the Calpha−H bond of amides is the least acidic among the carbonyl derivatives, thereby making it challenging to develop highly efficient and selective transformations based on amides. Reactivity umpolung refers to the reversion of polarity of a functional group. The idea of inverting the innate polarity of organic functional groups, initially introduced by Wittig and later popularized by Seebach, marks a pivotal conceptual breakthrough in organic synthesis. In contrast to the progress for the umpolung of aldehyde, the umpolung of amides has proved challenging and only recently made notable progress. Following the elegant design, the C1 of the amide can become nucleophilic, and the C2 can be electrophilic. In this review, we attempt to summarize the reported examples that are broadly categorized as reactivity umpolung of amides. This review is structured around the umpolung of C1 through radical or carbanion reactions, as well as the umpolung of C2 through electrophilic amide activation or the unique properties of Weinreb amide.

An innovative approach for the synthesis of 4Tris@Porphyrin and anderson polyoxometalate based covalent organic framework to reveal its potential for photocatalytic properties

Herein, a polyhydroxy containing metallo porphyrin linked through amide functional group with Anderson polyoxometalate (POM) was used to form TPMnA-COF. Structure and applications have been unlocked thoroughly by means of FT-IR, UV–visible, 1HNMR, PXRD, SEM and cyclic voltammetric (CV) spectral analysis. The TPMnA-COF was tested as catalyst to explore the photocurrent and photodegradation properties. ITO electrode was fabricated to study optical activity, absorption study and photocurrent generation. The adsorption study of TPMnA-COF has been studied using Langmuir and Freundlich model with calculated Langmuir constants qm, KL, RL and R2 values of about 12.42 mg/g, 0.33 M-1, 0.30 and 0.98 respectively. The 1/n, Kf and R2 values obtained from Freundlich adsorption isotherm were 0.70, 3.16 M-1 and 0.96 respectively. The band gap value evaluated via absorption edge of UV–visible spectra in DMSO solution was 2.75 eV while the band gap value calculated for ultra-thin film was 1.95 eV. The calculated real, imaginary dielectric constants, Urbach edge, refractive index and the electrical conductivity values for ultra-thin film of TPMnA-COF were 518.8, 2.9 × 10−11-8.1 × 10−11, −3.802 meV, 22.8–22.6 and 8.3 × 104−3.4 × 104 S/m), respectively. Responsivity for film was also tested using purple, blue, green, yellow, orange and red colourlights and the observed responsivity for different lower light intensities were 3.05, 2.9, 1.6, 1.55, 1.5 and 1.4 mA/W respectively. Furthermore, photodegradation activity of TPMnA-COF in Methylene-Blue (MB) and Rhodamine B(Rh–B) dyes under 3 W light. The results showed higher photocatalytic efficiency for Rh–B than that for MB with obtained degradation efficiency of 81 % and 60.4 %, respectively after 660 min. The scavengers such as ammonium oxalate (AO, h+), isopropanol (ISOP, •OH), catalase (CAT, H2O2) and superoxide dismutase (SODM, O2−●) were used to find out the effectiveness of each reactive specie to degrade the dyes solution in the mechanism of degradation. It was observed that AO (h+) and ISOP(•OH) were more active species in the photodegradation mechanism than CAT(H2O2) and SODM(O2−●).

Biodegradable amidequats, derivatives of caprylic and pelargonic acids as cationic surfactants for agricultural applications

In this study, we proposed to incorporate natural herbicides i.e. caprylic and pelargonic acids into an amide functional group of a cationic surfactant, thus obtaining amidequats. All the obtained amidequats can be classified as ionic liquids since their melting point values were below 100 °C. Moreover, all compounds were stable up to 166 °C. The obtained ionic liquids exhibited high surface activity, as confirmed by their low CMC values (ranging from 0.02 to 4.32 mmol·L−1) as well as their ability to efficiently lower the surface tension (to 23.8–30.2 mN·m−1). The amidequats, derivatives of caprylic and pelargonic acid exhibited different foam formation ability and its stability depending on their structure. Subsequent tests indicated that amidequats comprising the decyl and dodecyl substituents were readily biodegradable (mineralization at 63–78 % within 10 days). They did not significantly affect the germination of the model monocotyledon plant (sorghum) up to 500 mg·L−1, however, they showed phytotoxicity in relation to the model dicotyledon weed (common sunflower) and displayed low or moderate toxicity towards model microorganisms commonly found in soil, which confirms their low environmental impact.

Inter-/intra-molecular synergism improve self-assembly behavior of hydroxamate-modified amino acid surfactant for flocculation of micro-fine particles

Flotation recovery of micro-fine minerals has been constrained by low flotation efficiency due to the large surface area and small quality of fines, causing a huge waste of valuable resources. Herein, we developed a novel hydroxamate-modified N-acyl amino acid surfactant, 2-decanoylamino-4-hydroxycarbamoyl-butyric acid (DHBA), which can self-assemble via synergism among amide, carboxyl, and hydroxamate functional groups for achieving the efficient flocculation and recovery of fine rhodochrosite. The theoretical calculations and interface analyses revealed from microscopic perspective that the intramolecular synergistic chelation effect between carboxyl and hydroxamate groups conferred strong adsorption affinity of DHBA on rhodochrosite. On the other hand, the intermolecular H-bonds not only promote the tight arrangement of collectors on particle surface to enhance hydrophobic association effect, but also induce the agglomeration of collectors into net-like “macromolecules” clusters to produce adsorption bridging for fines. Eventually, the flocculation and flotation tests confirmed that DHBA exhibits a superior flocculation and collecting performance for fine rhodochrosite than very common collector octanoylhydroxamate acid (OHA) (the recovery reached 95.2% for 1 × 10−4 mol·L−1 DHBA while 66.8% for OHA). This research provides a feasible surfactant development strategy for flocculation-flotation.

One-pot hydrothermal green synthetic approach of fluorescent carbon dots as optical probes for 2-nitrophenol

The pursuit of a cost-effective and green synthetic approach to chemical sensors and their application in the sensing of toxic and harmful substances is a never-ending exercise for scientists and researchers. Preparation of fluorescent carbon dots (C-dots) from biomass using water as a solvent and a hydrothermal autoclave to provide the required synthesis temperature offers a cheap and environmentally friendly synthetic approach. Herein, we report a faster, less costly and ecofriendly hydrothermal synthetic approach of carbon dots from Citrullus vulgaris peels as a precursor. The as-prepared carbon dots exhibited hydroxyl, carbonyl and amide functional groups on the surface and an amorphous structure with a particle size distribution of 1.7–3.0 nm. Moreover, the carbon dots displayed intense blue emission fluorescence at 470 nm after excitation at 400 nm. The as-prepared carbon dots demonstrated effective application without further modification towards the selective and sensitive optical recognition of 2-nitrophenol used in the manufacture of explosives. A limit of detection of 2.28×10−7 M was achieved, and no fluorescence quenching was observed in the presence of other nitroaromatic and benzene derivatives indicating excellent selectivity towards 2-nitrophenol. Finally, further studies are required to investigate the potential for the as-prepared carbon dots to monitor nitroaromatic pollutants in real environmental systems.

Reduction of hexavalent chromium using Bacillus safensis isolated from an abandoned mine

ABSTRACT The present work focused on the isolation of a bacterial strain multi-resistant to heavy metals with a high potential for reducing hexavalent chromium (Cr(VI)) and studied its Cr(VI) removal performance in immobilized state and the mechanisms involved. Bacterial isolate was identified as Bacillus safensis CCMM B629 (B. safensis), is able to completely reduce 50, 100 and 200 mg/L of Cr(VI) after 24, 48 and 120 h, respectively under optimized conditions of pH 7 and 30°C. The coexistence of nitrates, cadmium and mercury inhibits reduction, while copper and iron significantly improve removal efficiencies. Additionally, the presence of electron donors such as glycerol, glucose and citrate significantly increases bioreduction rate. Cells immobilized in alginate beads successfully reduced Cr(VI) compared to free cells, showing the performance of biobeads in Cr(VI) reduction. Membrane fraction exhibited highest rate of Cr(VI) reduction (65%) compared to other cellular components, indicating that Cr(VI) reduction occurred primarily in cell membrane. Further characterization of Cr(VI) removal by B. safensis cells using scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis showed its ability to reduce and adsorb Cr(VI), confirming that hexavalent chromium was taken up successfully on bacterial cell surfaces. Based on Fourier transform infrared spectroscopy analysis (FTIR), hydroxyl, carboxyl, amide, and phosphoryl functional groups participated in combination with Cr(III). In conclusion, B. safensis is a bacterium with great potential for Cr(VI) removal, and it is a promising and competitive strain for use in bioremediation of Cr(VI) contaminated industrial effluents.

Enhancement in toughness of cement pastes by chitosan modified with polyacrylic acid (CS/PAA): Microstructure evolution and molecular dynamics

This paper presents the preparation and utilization of chitosan modified with polyacrylic acid (CS/PAA), which possesses abundant hydroxyl, carboxyl, and amide functional groups, to examine its impact on the mechanical properties and hydration process of cement paste, as well as the morphology of hydration products, particularly portlandite.The results show that the addition of CS/PAA can extend the induction period of C3S hydration by facilitating the complexation between Ca2+ and carboxyl, which is not noteworthy due to the competitive adsorption between CS/PAA and C3S, C3A in cement pastes. Furthermore, the (001) crystal plane of calcium hydroxide (CH) can undergo a transformation from hexagonal columnar crystals to lamellar crystals through the oriented adsorption of CS/PAA. These lamellar crystals can serve as local strengthening zones, aiding the cement paste in achieving higher flexural strength without compromising compressive strength. Hopefully, the regulation mechanism of CS/PAA on the morphology and stacking of CH can make a guidance for the application of CS/PAA in cement based materials with high compressive strength and toughness.

Ruthenium-Catalyzed Aminocarbonylation with Isocyanates Through Weak Coordinating Groups.

Introducing amide functional groups under mild conditions has growing importance owing to the prevalence of such moiety in biologically active molecules. Herein, we disclose a mild protocol for the directed ruthenium-catalyzed C-H aminocarbonylation with isocyanates as the amidating agents developed through high-throughput experimentation (HTE). The redox-neutral and base-free reaction is guided by weakly Lewis basic functional groups, including anilides, lactams and carbamates to access anthranilamide derivatives. The synthetic utility of this transformation is reflected by large-scale synthesis and late-stage functionalization.

Molecular Dynamics Simulation of Polyacrylamide Adsorption on Calcite.

In poorly consolidated carbonate rock reservoirs, solids production risk, which can lead to increased environmental waste, can be mitigated by injecting formation-strengthening chemicals. Classical atomistic molecular dynamics (MD) simulation is employed to model the interaction of polyacrylamide-based polymer additives with a calcite structure, which is the main component of carbonate formations. Amongst the possible calcite crystal planes employed as surrogates of reservoir rocks, the (1 0 4) plane is shown to be the most suitable surrogate for assessing the interactions with chemicals due to its stability and more realistic representation of carbonate structure. The molecular conformation and binding energies of pure polyacrylamide (PAM), hydrolysed polyacrylamide in neutral form (HPAM), hydrolysed polyacrylamide with 33% charge density (HPAM 33%) and sulfonated polyacrylamide with 33% charge density (SPAM 33%) are assessed to determine the adsorption characteristics onto calcite surfaces. An adsorption-free energy analysis, using an enhanced umbrella sampling method, is applied to evaluate the chemical adsorption performance. The interaction energy analysis shows that the polyacrylamide-based polymers display favourable interactions with the calcite structure. This is attributed to the electrostatic attraction between the amide and carboxyl functional groups with the calcite. Simulations confirm that HPAM33% has a lower free energy than other polymers, presumably due to the presence of the acrylate monomer in ionised form. The superior chemical adsorption performance of HPAM33% agrees with Atomic Force Microscopy experiments reported herein.

Single-ion conductors functionalized graphene oxide enabling solid polymer electrolytes with uniform Li-ion transport toward stable and dendrite-free lithium metal batteries

The utilization of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) has long been deemed promising for the application of state-of-the-art lithium metal metals (LMBs), but still severely impeded by the insufficient Li-ion transporting channels and inhomogeneous Li deposition. Herein, the design of single-ion conductors (PSLi) modified graphene oxide nanosheets (GO-PSLi)-reinforced PEO-based SPEs to address these long-standing issues is proposed. The electronegative sulfonate-rich groups with lithiophilic features on GO-PSLi surface not only effectively enhance the dispersion of nanoparticles within the PEO matrix, but also provide fast Li-ion diffusion pathways. Meanwhile, introducing PSLi chains is also favorable to highly reducing the crystallization of composite SPEs through hydrogen interactions derived from the desired amide functional groups. This, in turn, facilitates segmental relaxation of the PEO backbone, leading to accelerates the Li-ion migration. As a proof of concept, the as-prepared composite SPEs demonstrate a good ionic conductivity of 2.2 × 10−4 S cm−1 and a high lithium transference number of 0.53, significantly outperforming the pure PEO SPEs (1.0 × 10−4 S cm−1 and 0.28, respectively) at 60 °C. In addition, the symmetrical Li||Li cells based on the composite SPEs show excellent reversible lithium plating/stripping performances with dendrite-free uniform lithium deposition over 1100 h under a current of 0.1 mA cm−2 at 60 °C. The Li||LiFePO4 batteries also achieve an impressive capacity of 120.2 mAh g−1 at a high current density of 4C and deliver remarkable cycling abilities with 84.6% retention after 250 cycles under 1C at 60 °C. This study offers a facile and practical strategy to develop advanced composite PEO-based SPEs for safe and dendrite-free solid-state LMBs.

Starch-Based Polymer Materials as Advanced Adsorbents for Sustainable Water Treatment: Current Status, Challenges, and Future Perspectives.

Over the past three decades, chemical and biological water contamination has become a major concern, particularly in the industrialized world. Heavy metals, aromatic compounds, and dyes are among the harmful substances that contribute to water pollution, which jeopardies the human health. For this reason, it is of the utmost importance to locate methods for the cleanup of wastewater that are not genuinely effective. Owing to its non-toxicity, biodegradability, and biocompatibility, starch is a naturally occurring polysaccharide that scientists are looking into as a possible environmentally friendly material for sustainable water remediation. Starch could exhibit significant adsorption capabilities towards pollutants with the substitution of amide, amino, carboxyl, and other functional groups for hydroxyl groups. Starch derivatives may effectively remove contaminants such as oil, organic solvents, pesticides, heavy metals, dyes, and pharmaceutical pollutants by employing adsorption techniques at a rate greater than 90%. The maximal adsorption capacities of starch-based adsorbents for oil and organic solvents, pesticides, heavy metal ions, dyes, and pharmaceuticals are 13,000, 66, 2000, 25,000, and 782 mg/g, respectively. Although starch-based adsorbents have demonstrated a promising future for environmental wastewater treatment, additional research is required to optimize the technique before the starch-based adsorbent can be used in large-scale in situ wastewater treatment.

Waste biomass from hypersaline potash mining byproducts: Detection and visualization of Cu(II) and Cr(VI) on Croceicoccus sp. FTI14 biosorbent

Microorganisms in hypersaline potash mining byproducts and their potential environmental applications have not been extensively reported. This study reports the diverse waste-impacted microbial communities (archaea and bacteria) adapted to extreme salinity (>10–25%). Of these, halotolerant Croceicoccus sp. FTI14 was investigated as a biosorbent for removing dissolved Cu(II) and Cr(VI) from synthetic Cu(II) and Cr(VI)-contaminated DI, groundwater and saline groundwater (0.55 M ionic strength). FTI14 biomass was oven-dried, finely ground, and investigated in batch biosorption experiments. At initial metal concentrations of 40 mg/L, FTI14 removed 40 ± 0.7% (16.3 ± 0.5 mg/g) and 19 ± 0.1% (7.8 ± 0.1 mg/g) of the Cu(II) from deionized water and saline groundwater, respectively, while only 22.9 ± 0.7% (9.6 ± 0.2 mg/g) and 2.1 ± 0.6% (1.0 ± 0.3 mg/g) Cr(VI) removal was achieved. Cu(II) uptake (mg/g) exceeded Cr(VI) uptake by a factor of 1.7–7.8. Langmuir and Freundlich models were applied on FTI14 biosorption isotherm data. The Freundlich model showed a better fit for both Cu(II) and Cr(VI), as indicated by the AIC values compared with evidence ratios. Synchrotron-based scanning transmission X-ray microscopy (STXM) visualizations of the biosorbent showed a mixture of whole cells and indistinct biomass and a spatial association between metals and biomass. Metal exposure alters the amide functional groups peak in Fourier transform Infra-red (FTIR) spectra, suggesting its role in sorption process. Thus, this study indicates culturable halotolerant microorganisms from hypersaline potash mining byproducts and its potential as biosorbent applications for metal removal from impacted groundwater.

Synthesis of N, S co-doped carbon quantum dots (N,S-CQDs) for sensitive and selective determination of mercury (Hg2+) in Oreochromis niloctus (Tilapia fish)

This study reported the synthesis of green-emitting N,S-doped carbon quantum dots (N,S-CQDs) through a one-step, facile, and fast hydrothermal technique using citric acid, glutamine, and Na2S as the carbon, nitrogen, and sulphur sources respectively. The fluorescence efficiency of the developed nanosensor was investigated by varying the duration of synthesis (4, 5, and 6 h). Characterization of the N-CQDs was achieved using Fourier-Transform Infra-red Spectroscopy (FTIR), High-resolution transmission electron microscope (HRTEM), ultraviolet–visible spectroscopy (UV–Vis), and X-Ray diffraction analysis (XRD). The as-synthesized N,S-CQDs are small (average size of 3.45 ± 0.86 nm), spherical, and displayed green emission (535 nm) with a fluorescent quantum yield (QY) of 10.35%. FTIR analysis reveals carboxylic, hydroxyl, and conjugated amide functional groups. The fluorometric study showed that the developed nanosensor was selective and sensitive towards Hg2+ ions in the midst and absence of interfering ions with a detection limit (LOD) of 28.9 nM. The static quenching mechanism was proposed based on lifetime and UV results. Furthermore, it was used as a nanoprobe for Hg2+ determination in Oreochromis niloctus with recoveries of 96.7–108.6% (RSD < 4.1%), indicating the as-synthesized N,S-CQDs have potentials as a nanoprobe for Hg2+ determination in sea foods.

Adsorption characteristics of bovine serum albumin on the surface of 316L stainless steel coated with diethoxydimethylsilane/chitosan composite films

In this study, diethoxydimethylsilane (DEDMS) was blended with chitosan (CS) to fabricate DEDMS/CS composite films, which were deposited on the surface of 316L stainless steel to assess their anticoagulant properties. A neat CS film exhibits a high concentration of bovine serum albumin (BSA) protein adhesion of 458.3 ± 6.2 μg/L in a bicinchoninic acid protein assay because the carbonyl and amide functional groups on the CS surface easily form hydrogen bonds with the carboxylic acid functional groups of the BSA protein. The DEDMS/CS composite films exhibited lower BSA adhesion concentration than neat CS films because some of the carbonyl and amide functional groups on the surface of CS were replaced by the –Si-O-Si and –Si-(CH3)2 functional groups. Increasing the DEDMS content in the DEDMS/CS composite films led to a higher concentration of –Si-O-Si and –Si-(CH3)2 functional groups on the surface and lower BSA adhesion concentration. Blending excess amounts of DEDMS caused an undesirable rougher surface morphology because of the hydrolysis and self-condensation reactions of DEDMS; this deteriorated the anticoagulant properties of the composite films. The study confirmed that a DEDMS/CS composite film with an appropriate DEDMS/CS content ratio of 8/92 mL/mL possesses hydrophobic characteristics and the lowest BSA protein adhesion of 155.5 ± 1.0 μg/L and has potential for biomedical coating applications.