CHNS Elemental Analysis Research Articles

Hydrothermal Liquefaction of Food Waste: Effect of Process Parameters on Product Yields and Chemistry

Increasing food waste generation (1.6 billion tons per year globally) due to urban and industrial development has prompted researchers to pursue alternative waste management methods. Energy valorization of food waste is a method that can reduce the environmental impacts of landfills and the global reliance on crude oil for liquid fuels. In this study, food waste was converted to bio-crude oilviahydrothermal liquefaction (HTL) in a batch reactor at moderate temperatures (240–295°C), reaction times (0–60 min), and 15 wt.% solids loading. The maximum HTL bio-crude oil yield (27.5 wt.%), and energy recovery (49%) were obtained at 240°C and 30 min, while the highest bio-crude oil energy content (40.2 MJ/kg) was observed at 295°C. The properties of the bio-crude oil were determined using thermogravimetric analysis, fatty acid methyl ester (FAME) analysis by gas chromatography with flame ionization detection, CHNS elemental analysis, and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectroscopy (FT-ICR MS). FT-ICR MS results indicated that the majority of the detected compounds in the bio-crude oil were oxygen-containing species. The O4class was the most abundant class of heteroatom-containing compounds in all HTL bio-crude oil samples produced at 240°C; the O2class was the most abundant class obtained at 265 and 295°C. The total FAME content of the bio-crude oil was 15–37 wt.%, of which the most abundant were palmitic acid (C16:0), palmitoleic acid (C16:1), stearic acid (C18:0), and polyunsaturated fatty acids (C18:3N:3, C18:3N:6).

Facile synthesis of Co3O4 and ZnO nanoparticles by thermal decomposition of novel Co(II) and Zn(II) Schiff base complexes for studying their biological properties and photocatalytic degradation of crystal violet dye

Utilizing the metal complexes as low-cost precursors for the synthesis of metal oxide nanoparticles has been regarded as one of the most suitable and practical techniques that produce nanoparticles with low crystallite sizes. So, in this paper, Co3O4 and ZnO nanoparticles were facilely synthesized by thermal decomposition of novel Co(II) and Zn(II) Schiff base complexes. The Schiff bases, which were abbreviated as E1 and E2, were synthesized by condensation of 4-amino-5-ethyl-4H-1,2,4-triazole-3-thiol with 4-(dimethylamino)benzaldehyde and 2,4-dihydroxybenzaldehyde, respectively. The Co(II) and Zn(II) complexes were synthesized by condensation of Schiff bases with CoCl2•6H2O and ZnCl2, respectively. The Schiff bases, complexes, and nanoparticles were characterized using different tools such as 1HNMR, FT-IR, CHNS elemental analysis, TGA thermal analysis, XRD, HR-TEM, and UV–Vis spectrophotometer. The average crystallite size of ZnO samples, which were synthesized from the ignition of ZnE1 and ZnE2 complexes, is 34 and 44 nm, respectively. The average crystallite size of Co3O4 samples, which were synthesized from the ignition of CoE1 and CoE2 complexes, is 33 and 45 nm, respectively. The Co3O4 and ZnO nanoparticles were utilized for the photocatalytic degradation of crystal violet dye in aqueous media under UV illumination in the presence of hydrogen peroxide. The maximum% degradation of crystal violet dye using ZnO in the absence and presence of H2O2 is 78 and 98%, respectively. The maximum% degradation of crystal violet dye using Co3O4 in the absence and presence of H2O2 is 67 and 95%, respectively. Furthermore, the biological activities of the synthesized samples were studied against some bacterial and fungal strains. The complexes show moderate effect against bacterial strains whereas did not show any effect against fungal strains except ZnE1, CoE2, and ZnE2 which have moderate effect against Candida albicans fungi. The Co3O4 and ZnO nanoparticles show moderate effect against bacterial strains and did not show any effect against fungal strains.

Sodium Dodecylbenzene Sulfonate-Modified Biochar as An Adsorbent for The Removal of Methylene Blue

Biochar is an interesting adsorbent material due to its use is correlated with biomass waste utilization and also minimize environmental pollution from high amount of biomass by-product. Regarding to improve the biochar ability in water treatment, several surface modifications have been developed, one of them is modification using surfactant. In this study, sodium dodecylbenzene sulfonate (SDBS) was used to modify the surface of biochar prepared from pyrolysis of cassava peels (Manihot utilissima). Its performance in biochar modification to remove methylene blue (MB) dyes was compared with sodium dodecyl sulphate (SDS) surfactant for observing the important of – interactions mechanisms. The analysis of biochar and biochar-SDBS were conducted by using Fourier transform infrared (FTIR), CHNS elemental analysis, and scanning electron microscope (SEM). Furthermore, the adsorption experiments were conducted using UV-Vis spectrophotometer. It is known that modification using SDBS could increase the adsorption capacity of biochar not only from electrostatic interaction but also through – interactions mechanisms. In this respect, as the amount of SDBS mass increased, the adsorption capacity was also improved due to the modification produced more active cites on biochar. The maximum MB adsorption onto biochar-SDBS occurred at adsorbent mass of 15 mg with optimum pH value of 10. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Preparation of amine–modified lignin and its applicability toward online micro–solid phase extraction of valsartan and losartan in urine samples

In the present work, with the focus on an environmentally–friendly approach, some gels were prepared by synthesizing amine–modified lignin, extracted from sugarcane bagasse, and further esterification and subsequent freeze–drying. These lignin–based gels were implemented as extractive phases in an online micro–solid phase extraction (μSPE) setup in conjunction with high performance liquid chromatography (HPLC) with UV detector. The developed method was used for analytical determination of valsartan and losartan in urine samples. To study the effect of the functionalization process, the efficiency of the unmodified lignin and the functionalized lignin were compared both in the absence and the presence of graphene oxide (GO), presumably as a suitable doping agent. Surprisingly, higher extraction efficiency for the functionalized lignin, compared to both unmodified lignin and GO was observed. The amination process for the prepared gel was analyzed and proved by CHNS elemental analysis and Fourier transform infrared (FT-IR) spectroscopy. The morphology of sorbet was investigated via scanning electron microscope (SEM) imaging and a nanoscale cauliflower feature was observed. The method was optimized and subsequently applied to the analysis of the urine samples. Limits of detection (LOD) of 8 and 6 µg L − 1, limits of quantification (LOQ) of 27 and 20 µg L − 1 and linear dynamic range (LDR) of 27–2000 and 20–2000 µg L − 1 with intraday relative standard deviations (RSD%) of 4 and 3% were obtained for valsartan and losartan, respectively. The whole online μSPE–HPLC setup was conveniently used for the analysis of a patient urine sample and a quantity of 352 μg L − 1 of losartan was found. Acceptable relative recoveries (109–108 and 95–94% for valsartan and losartan) revealed the analytical potential of the method for the determination of drugs in complex urine samples.

PREPARATION AND CHARACTERIZATION OF MAGNESIUM/ALUMINIUM LAYERED DOUBLE HYDROXIDE AS FILLER IN LOW-DENSITY POLYETHYLENE COMPOSITE

Polymer had been widely used in industries nowadays. However, the properties of the polymer itself are limited to a particular application. This study describes synthetic clay, layered double hydroxide (LDH), as a filler in low-density polyethylene (LDPE) composite. LDHs of magnesium/aluminium-dodecyl sulfate (Mg/Al-DS) and its grafted with triethoxymethylsilane (TEMS), (TEMS-g-Mg/Al-DS) were synthesized through co-precipitation and salinization reaction methods. The presence of alkyl group, v(C-H) in both LDH had confirmed through Fourier transform infrared (FTIR). The appearance of peaks in FTIR spectra within the absorbance range of 2800 – 2930 cm-1 indicates a successful surface modification of LDH, supported by the changes of interlayer spacing and the presence of carbon from X-ray diffractogram and CHNS elemental analysis, respectively. The synthesized LDH was mixed with LDPE via melt intercalation method. The LDH modification resulted in higher interaction and compatibility between the LDPE matrix and LDH by the formation exfoliated type of nanocomposites, as suggested by XRD analysis.

The Impact of AN Contribution on the Thermal Characteristics and Molecular Dynamics of Novel Acrylonitrile-Styrene-Styrene Sodium Sulfonate Terpolymers.

We performed a free radical solution polymerization of new acrylonitrile (AN), styrene (St) and styrene sodium sulfonate (SSS) acceptor–donor acceptor monomer systems. The compositions and structures of the produced terpolymers were elucidated using CHNS elemental analysis, and Fourier transform infrared (FTIR) spectroscopies. Three terpolymers candidates were chosen for detailed thermal investigations, where the AN molar ratio varied almost threefold (from ~6.9% to ~17.4%) while the molar ratios of St and SSS varied slightly, at average values around 76.0% and 12.9%, respectively. The glass transition (Tg) values of the terpolymers were measured calorimetrically. In addition, thermal gravimetric analyses (TGA) of the samples were conducted in the temperature range from room temperature to 800 °C. All terpolymers exhibited a single Tg value, indicating random copolymerization of the monomeric species. TGA results revealed that variation of the AN molar ratio had a significant influence on the thermal stabilities of the terpolymers. The impact of AN contribution on the molecular dynamics of the glass transition in the terpolymers was explained quantitatively in a framework of a molecular model.

Eco-friendly polyelectrolyte nanocomposite membranes based on chitosan and sulfonated chitin nanowhiskers for fuel cell applications

Novel sulfonic acid-functionalized chitin nanowhiskers (sChW) with enhanced proton conductivity were prepared for fabricating green and environmentally friendly chitosan (CS)-based nanocomposite polymer electrolyte membranes (PEMs). The performance of sChW in the development of direct methanol fuel cell (DMFC) nanocomposite membranes was also assessed. The manufactured nanocomposite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), CHNS elemental analysis, X-ray diffractometry (XRD), ion-exchange capacity (IEC), water uptake, as well as proton conductivity and methanol permeability. The results showed that modification of chitin nanowhiskers (ChW) with sulfonic acid groups, as the proton-conducting sites, could enhance proton conductivity of the manufactured membranes, leading to a fall in methanol permeability, as a result of attractive interactions between the negatively charged sulfonic acid groups on the surface of sChW and the positively charged amine groups in the chitosan chains. Thus, the selectivity parameter (the ratio of the proton conductivity to methanol permeability) of the chitosan-based nanocomposite membranes significantly increased from 3900 for pristine chitosan PEM to 26,888 S.s.cm−3 (ca. 6.8 times) for a membrane with 5% (wt) sChW. The functionalization strategy used herein can pave the way for the development of efficient polyelectrolyte membranes for applications in direct methanol fuel cells.

Spad index for diagnosis of nitrogen status in ‘Esmeralda’ peach

Abstract The objective of this research was to evaluate the technical feasibility of SPAD index in the diagnosis of N status in ‘Esmeralda’ peach. The field trial, with five N rates applied to the soil (0, 40, 80, 120 and 160 kg ha-1 of N as urea form) was conducted in a randomized block design with four replications. During the years 2014, 2015, 2016 and 2017, SPAD readings were carried out with a Minolta SPAD-502 chlorophyll meter, in the leaf middle part, in 40 leaves per plot. The leaf N content determination was performed in CHN-S Elemental Analyzer. SPAD index and leaf N content increased in a linear way in response to increasing N rates applied in soil. There was a positive linear correlation between SPAD index and N concentration in leaves (0.652; 0.756; 0.762 and 0.767, p<0.05). SPAD index can be used for nutritional N diagnosis purpose in peach when readings are taken between the 13th and 15th weeks after full bloom. In the range between 39 and 49, the SPAD index indicates the leaf N content is included in “normal” class (33 – 45 g kg-1) of agronomic interpretation for the States of Rio Grande do Sul and Santa Catarina, Brazil.

The Influence of Microbial Inoculants on Micro- and Macronutrients on Calcaric Alluvial Soil, Buzău, Romania

The EU, having the overarching goal to become the first climate-neutral continent by 2050, plans to consolidate food chains that works for all: consumers, producers, climate, and the environment. For this, we need to reduce dependency on pesticides, reduce the excess fertilization, promote the biodiversity in agroecosystems, including on soils. Therefore, practical solutions using microbial inoculants to protect crops, restore soil health and functions, and improve plants health are enforced. Some fungal inoculants function both as entomopathogens and endophytes; colonizing a wide variety of plants, favoring plant growth, and protecting crops against pests. In this context, the present study aimed to evaluate the variation of total content of macro and micronutrients from soil in the context of application of microbial inoculants based on diverse benefic species, in an experimental field, under conversion to organic farming. The soil samples were taken from 0-20 cm depth, dried and analyzed by CHNS elemental analyzer and ICP-MS. The results shown some correlations between microbial inoculants and macro and micronutrients content, which can be further exploited inside the organic or sustainable production systems by farmers.

Green, homogeneous oxidation of alcohols by dimeric copper(II) complexes

Three pyrazole derivatives, 3,5-dimethyl-1H-pyrazole (DMPz) (I), 3-methyl-5-phenyl-1H-pyrazole (MPPz) (II), and 3,5-diphenyl-1H-pyrazole (DPPz) (III), were prepared via reacting semicarbazide hydrochloride with the acetylacetone, 1-phenylbutane-1,3-dione, and 1,3-diphenylpropane-1,3-dione, respectively. Complexes 1–3 were isolated by reacting CuCl2·2H2O with I–III, respectively, and characterized by CHNS elemental analyses, FT-IR, UV-Vis, 1H and 13C NMR, EPR spectra, and TGA/DTA. Molecular structures of the pyrazole derivatives I–III and copper(II) complexes 2 and 3 were studied through single-crystal XRD analysis to confirm their molecular structures. Overlapping of hyperfine splitting in the EPR spectra of the dimeric copper(II) complexes 1–3 indicates that both copper centers do not possess the same electronic environment in solution. The copper(II) complexes are dimeric in solid state as well as in solution and catalyze the oxidation of various primary and secondary alcohols selectively. Catalysts 1–3 show more than 92% product selectivity toward ketones during the oxidation of secondary alcohols. Surprisingly primary alcohols, which are relatively difficult to oxidize, produce carboxylic acid as a major product (48%–90% selectivity) irrespective of catalytic systems. The selectivity for carboxylic acid rises with decreasing the carbon chain length of the alcohols. An eco-friendly and affordable catalytic system for oxidation of alcohols is developed by the utilization of H2O2, a green oxidant, and water, a clean and greener solvent, which is a notable aspect of the study.

Preparation and characterization of sulfur-vinylbenzyl chloride polymer under optimized reaction conditions using inverse vulcanization

Inverse vulcanization offers a new method to make value to this cheap and highly abundant sulfur to produce sulfur-based polymers for different applications. However, most of the research done so far dealt with the characterization of the polymers or their efficiency in certain applications. Here, 4-vinylbenzyl chloride (VBC) is reacted with sulfur under optimized reaction conditions to produce linear sulfur-based polymer. Response Surface Methodology (RSM) is employed to optimize the reaction conditions in terms of reaction temperature, reaction time, and initial sulfur content. The properties of the polymer produced under optimized conditions are then evaluated using proton nuclear magnetic resonance (1H NMR), CHNS elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), powder X-Ray diffraction (PXRD), and field emission scanning electron microscopy (FESEM). The formation of the polymer and full conversion of the monomers were confirmed by NMR and CHNS analysis. The S/VBC polymer showed a uniform morphology and smooth surface. The polymer demonstrated an amorphous structure with a low Tg (3.7 °C), high thermal stability (205 °C), and great stability against depolymerization by time. The S/VBC polymer is significant due to its ability for post-functionalization which makes it possible to introduce new applications to sulfur-based polymers.

Production of renewable hydrocarbons from vegetable oil refining by-product/waste soapstock over selective sulfur-free high metal loading SiO2–Al2O3 supported Ni catalyst via hydrotreatment

The performance, selectivity, recovery, and reusability of high metal loading commercial Ni66 ± 5%/SiO2–Al2O3 catalyst were studied in renewable hydrocarbon synthesis from low cost raw material pretreated soapstock (TS) by solvent-free one-pot hydrotreatment (HT). TS was extracted from rapeseed oil chemical refining by-product/waste soapstock (SS) by developed simple treatment method. The catalyst was characterized by FE-SEM, TEM, XRF, XRD, and N2 sorption analysis. Feedstock, liquid, and gaseous products were analyzed by FT-IR, GC-FID, GC-MS, GC-TCD, and CHNS elemental analysis. The effect of initial H2 pressure (2–8 MPa), catalyst amount (3–9%), reaction temperature (280–340 °C), and residence time (15–60 min) on hydrocarbon production were investigated. Combustible gases and pure marketable linear saturated hydrocarbons with high yield 79.1%, calorific value 47.22 MJ/kg, C/H ratio 5.6, and n-C17 content 82.7% were successfully produced from TS using minimum effective catalyst amount and reaction conditions: 5%, 6 MPa, 320 °C, and 30 min.

Extraction of lignocellulosic constituents from cow dung: preparation and characterisation of nanocellulose

Continuous growth of the livestock population over the years has led to the generation of huge livestock waste. Inadequate management of animal waste and its poor disposal poses a serious public health issue and also leads to environmental pollution. In the recent decade, the rational use of lignocellulosic biomass towards preparation of bioproducts such as biofuels and biotextile has come up as a promising alternative for the efficient utilisation of animal waste biomass. Hence, the current study is focused on the efficient utilisation of an abundant source of lignocellulosic constituents, i.e. cow dung by the extraction and estimation of cellulose, lignin, and hemicellulose, respectively by an optimised kraft pulping method. The extracted cellulose was evaluated for the degree of polymerisation and was further used for the preparation of nanocellulose which has a wide range of applications. Cellulose and nanocellulose so obtained were morphologically and spectroscopically characterised by SEM-EDX, CHNS elemental analysis, TEM, and FT-IR techniques. Further, nanocellulose was also evaluated for its physical properties such as crystallinity index and zeta potential, which revealed their good crystallinity and excellent particle stability profile. Hence, this study is an innovative approach towards the valorisation of cow dung waste biomass into useful biomaterial, i.e. nanocellulose.

Suspension assisted analysis of sulfur in petroleum coke by total-reflection X-ray fluorescence

The influence of the particle size distribution of a petroleum coke sample compared to its sulfur content was investigated. For this matrix, an optimization procedure of the Suspension Assisted Analysis (SAA) by Total-reflection X-Ray Fluorescence (TXRF) quantitative method was developed. SAA-TXRF sulfur recoveries were evaluated for three particle size distributions of the same coke sample. The sulfur recovery increased when the particle size distribution was smaller. The observed behaviour was correlated and validated with CHNS elemental analysis and microwave-assisted digestion TXRF measurements. The results indicate that the sulfur signal is strongly influenced by the particle size distribution and the deposition morphology of the petroleum coke material. This effect could be explained by the presence of a strong absorption effect for the sulfur signal in combination with the distortion of the X-ray Standing Waves (XSW) field observed between the analyte, S, and the elements Ti and Co, which were used as an internal standard. The variation in sulfur observed was up to 45.5% lower than the higher recovery obtained by CHNS. This investigation suggests that for an adequate application of the SAA-TXRF method in petroleum coke or similar matrices, careful optimization of the final particle dispersion of the ground coke is crucial and necessary. In this case, the use of a high- power ultrasound probe was the key.

Grafting Diels-Alder moieties on cellulose nanocrystals through carbamation

The Diels-Alder reaction is a promising click chemistry for the design of advanced materials from cellulose nanocrystals (CNCs). Transferring such chemistry to cellulose nanocrystals requires the precise grafting of reactive Diels-Alder moeities under heterogeneous conditions without compromising the nanocrystals morphology. In this study toluene diisocyanate is used as a spacer to graft Diels-Alder moieties viz the furyl and protected maleimido moieties onto cellulose nanocrystals. A factorial experimental design reveals that reaction time and reactant molar ratio positively affect the grafting efficiency, as evidenced by FTIR and CHNS elemental analysis. The surface degree of substitution was analyzed via CHNS elemental analysis and XPS and found to range between 0.05 to 0.30, with a good agreement between the two techniques. 13C CP/MAS NMR confirmed that the grafted moieties and CNCs are intact after reaction. Side reactions were also observed and their impact on performing controllable click chemistry between cellulose nanocrystals is discussed.

An experimental and DFT study on novel dyes incorporated with natural dyes on titanium dioxide (TiO2) towards solar cell application

Titanium dioxide (TiO2) thin films were deposited on fluorine tin oxide (FTO) coated glass substrate using spin-coating techniques and as-deposited films were sensitized with various dyes. A series of azo derivatives (2, 5a-b) having different structures were successfully prepared through the process of the azo coupling reaction. KAZO 6 was successfully synthesized by esterification of kojic acid obtained from sago waste with azo 5a. These azo dye were examined using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to obtain the vertical excitation, electron distribution, energy levels, band gap, and light-harvesting efficiency in the ground and excited state. The obtained values exhibited a good correlation with the experimental values. Efficiency enhancement was reported by the incorporation of KAZO 6 with curcumin extracted from turmeric. Spectroscopy and optical properties of synthesized dyes were characterized using CHNS elemental analysis, FTIR, 1H NMR, 13C NMR, and UV–Vis spectroscopies. KAZO 6 displayed an efficiency of 1.59% compared to azo derivatives 0.13–1.12%. The efficiency of KAZO 6 enhanced from 1.59 to 1.74% with the incorporation of turmeric dye.

An efficient Brønsted acidic polymer resin for the carbonylation of formaldehyde to glycolic acid

In the present work, a series of sulfonic polymer-based acid catalyst PDS-x’s was obtained by hydrothermal method. The physical and chemical properties of the catalysts were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, thermogravimetric analysis, Fourier transform infrared spectrometer, pyridine-adsorbing IR, acid–base titration, X-ray photoelectron spectroscopy, and CHNS elemental analysis. The carbonylation of formaldehyde was chosen as a probe reaction to test the catalytic performance. The results show that the content of acid sites and specific surface area can be adjusted by changing the molar ratio of sodium 4-vinylbenzenesulfonate (SVBS) to divinylbenzene (DVB). The catalyst performance results show that the PDS-x’s can efficiently catalyze glycolic acid synthesis. And a high glycolic acid yield up to 96% was obtained on PDS-2.1 due to its large specific surface area, plentiful mesoporosity as well as suitable acid concentration. This data are even higher than those on super-strong CF3SO3H and commercial resin Amberlyst-15. Moreover, the carbonylation of formaldehyde is a structure-sensitive reaction, the isolated and monolayer dispersed -SO3H is much more active than aggregated −SO3H. Furthermore, the catalyst has high stability.

Synthesis, characterization of carbon adsorbents derived from waste biomass and its application to CO2 capture

Waste Entada Rheedii shell (ERS) was used for the preparation of biochar-based adsorbents for CO2 capture at ambient conditions. Three types of adsorbents were prepared by treating ERS with acid, base and neutral condition. The physico-chemical properties of synthesized carbons were derived by X-ray diffraction, N2 adsorption, Fourier-transform infrared spectroscopy, 13C-Nuclear magnetic resonance spectroscopy, Laser Raman, Field emission scanning electron microscopy (FESEM), CHNS elemental and thermo gravimetric analysis. Characterization results indicated that the surface area and presence of basic sites in the carbon depended on the nature of pre-treatment of shell. The CO2 adsorption ability of the ERS derived carbons was tested at ambient temperatures. Carbon prepared after acid treatment showed superior CO2 adsorption capacity. The reasons for high CO2 adsorption behavior of the carbons were explained by its characteristics. The adsorption capacity in presence of moisture was also estimated. These carbon adsorbents also exhibited recyclability without any change in its adsorption capacity.

Solid-state ion recognition strategy using 2D hexagonal mesophase silica monolithic platform: a smart two-in-one approach for rapid and selective sensing of Cd2+ and Hg2+ ions.

Thepossibility of a multifunctional and reversible solid-state colorimetric sensor is describedfor the identification and quantification of ultra-trace Cd2+ and Hg2+ ions, using a honeycomb-structured mesoporous silica monolith conjoined with an indigenous chromoionophoric probe, i.e., 4-hexyl-6-((5-mercapto-1,3,4-thiadiazol-2-yl)diazenyl)benzene-1,3-diol (HMTAR). The amphiphilic probe is characterized using NMR, FT-IR, HR-MS, and CHNS elemental analysis. The structural and surface properties of the monolithic template have been characterized using p-XRD, XPS, TEM-SAED, SEM-EDAX, FT-IR, TG-DTA, and N2 isotherm analysis. The unique structural features and distinct analytical properties of the solid-state sensor proffer a strong response in selectively signaling the target analytes. The probe (HMTAR) exhibits a 1:1 stoichiometric binding ratio with the target ions (Cd2+ & Hg2+), with a visual color change from pale orange to dark red for Cd2+ (525nm, λmax), and topurple for Hg2+ (530nm, λmax), respectively, in the pH range 7.0-8.0. The influence of variousanalytical criteria such as pH, temperature, response kinetics, critical probe concentration, sensor quantity, matrix tolerance, linear response range, reusability, the limit of detection (LOD), and quantification (LOQ) has been investigatedto validate the sensor performance. The proposed method displays a linear signal response in the concentration range 5-100μg/L, with a LOD value of 2.67 and 2.90μg/L, for Cd2+ and Hg2+, respectively. The real-world efficacy of the sensor material has been tested with real and synthetic water samples with a significant recovery value of ≥ 99.2%, to authenticate its data reliability and reproducibility (RSD ≤ 3.53%). Graphical abstract.

Flexible Polyester Screen‐printed Electrode Modified with Carbon Nanofibers for the Electrochemical Aptasensing of Cadmium (II)

AbstractAn aptasensor was prepared by immobilising a biotinylated aptamer selected for Cd(II) on an activated carbon nanofiber (CNF) and streptavidin modified a screen‐printed electrode. The acid activated CNF was characterised by FTIR, CHNS elemental analysis and electron microscopy. Cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy (EIS) were used to characterise each step in the aptasensor preparation electrochemically. A detection limit of 0.11 ppb and a linear range of 2–100 ppb were obtained for Cd(II) with tolerance for other interfering species. The aptasensor was applied in real water samples and validated with ICPOES.