Innovative Strategy Based on a Novel Carbon-Black-β-Cyclodextrin Nanocomposite for the Simultaneous Determination of the Anticancer Drug Flutamide and the Environmental Pollutant 4-Nitrophenol

Disposable electrochemical sensor: Highly sensitive determination of nitrofurazone antibiotic in environmental samples and pharmaceutical formulations

The study presents the successful development of a new electrochemical sensor with low cost and disposability for application in nitrofurazone detection in environmental and pharmaceutical samples. The sensors were fabricated using materials obtained from local storage and conductive carbon ink. The modification of the screen-printed electrodes with the hybrid nanomaterial based on silver nanoparticles, carbon quantum dots, and carbon nanotubes showed synergistic contributions in the nitrofurazone electrooxidation, as observed in the wide linear range (0.008 at 15.051 μM), with a sensitivity of 0.650 μA/μM. The limit of detection obtained was 4.6 nM. Differential pulse voltammetry, cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction analysis, and high-resolution transmission electron microscopy were used to evaluate the electrochemical and structural characteristics. Studies of possible interferences were considered with nitrofurazone in the presence of the ions and organic molecules. The results were satisfactory, with a variation of 93.3% ± 4.39% at 100% ± 2.40%. The low volume used in the analyses (50 μL), disposability, high sensibility, selectivity, and low limit of detection are advantages that make the proposed sensor an electrochemical tool of high viability for the NFZ detection in environmental matrices and pharmaceutical formulations.

In situ construction of covalent-organic framework on hydrogen-bond organic framework: Fluorescence detection and removal of 4-nitrophenol and metamitron in aqueous media

A multifunctional COF@HOF (ETTA-DFP@TCBP-HOF) composite is prepared by adding red-fluorescent ETTA-DFP COF to the blue-fluorescent TCBP-HOF preparation system through molecular hydrogen bonding or π - π stacking interactions in situ one-pot synthesis. ETTA-DFP@TCBP-HOF is a multifunctional material for the quantitative detection and simultaneous adsorption of 4-nitrophenol (4-NP) and metamitron (MET) in aqueous solution. As a dual-emission fluorescent sensor, the ETTA-DFP@TCBP-HOF has both fluorescence of TCBP-HOF at 474 nm and ETTA-DFP COF at 592 nm, which shows a ratiometric response to 4-NP and MET with high selectivity, good sensitivity, good anti-interference performance and fast response. As a adsorbent, ETTA-DFP@TCBP-HOF displays rapid adsorption kinetics, and acceptable adsorption capacity for 4-NP and MET. In conclusion, this work constructs a novel multifunctional hybrid material with dual-emission center of HOF and COF, which can not only be used as a ratiometric fluorescent probe for detection, but also for removal of hazardous pollutants, suggesting a new strategy for environmental remediation and human health.

Simple and sensitive electrochemical sensing of amethopterin by using carbon nanobowl/cyclodextrin electrode

Resulted from the severe side effects, the development of inexpensive, simple and sensitive method for amethopterin (ATP, an antineoplastic drug) is very important but it still remains a challenge. In this work, low cost nanohybrid composed of carbon nanobowl (CNB) and β-cyclodextrins (β-CD) (CNB-CD) was prepared with a simple autopolymerization way and applied as electrode material to develop a novel electrochemical sensor of ATP. Scanning-/transmission-electron microscopy, Fourier transform infrared spectrum, photographic image and electrochemical technologies were utilized to characterize morphologies and structure of the as-prepared CNB and CNB-CD materials. On the basic of the coordination advantages from CNB (prominent electrical property and surface area) and β-CD (superior molecule-recognition and solubility capabilities), the CNB-CD nanohybrid modified electrode exhibits superior sensing performances toward ATP, and a low detection limit of 0.002 μM coupled with larger linearity of 0.005-12.0 μM are obtained. In addition, the as-prepared sensor offers desirable repeatability, stability, selectivity and practical application property, confirming that this proposal may have important applications in the determination of ATP.

Optimization of Electrochemical Sensitivity in Anticancer Drug Quantification through ZnS@CNS Nanosheets: Synthesis via Accelerated Sonochemical Methodology

Zinc sulfide/graphitic Carbon Nitride binary nanosheets were synthesized by using a novel sonochemical pathway with high electrocatalytic ability. The as- obtained samples were characterized by various analytical methods such as Transmission Electron Microscopy (TEM), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS) to evaluate the properties of ZnS@CNS synthesized by this new route. Subsequently, the electrical and electrochemical performance of the proposed electrodes were characterized by using EIS and CV to establish an electroactive ability of the nanocomposites. The complete properties like structural and physical of ZnS@CNS were analyzed. As-prepared binary nanocomposite was applied towards the detection of anticancer drug (flutamide) by various electrochemical methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry. The glassy carbon electrode modified with a ZnS@CNS composite demonstrates a remarkable electrocatalytic efficiency for detecting flutamide in a pH 7.0 (PBS). The composite modified electrode shows synergistic effect of ZnS and CNS catalyst. The electrochemical sensing performance of the linear range was improved significantly due to high electroactive sites and rapid electron transport pathways. Crucially, the electrochemical method was successfully demonstrated in biological fluids which reveals its potential real-time applicability in the analysis of drug.

High sensitivity, low-cost, and disposability: A novel screen-printed electrode developed for direct electrochemical detection of the antibiotic ceftriaxone

This study describes the development of a novel disposable and low-cost electrochemical platform for detecting the antibiotic ceftriaxone. The screen-printed electrode has been modified with a novel hybrid nanostructure containing silicon oxide (SiO2), zirconium oxide (ZrO2), and nitrogen-doped carbon quantum dots (Cdot-N). Different techniques like Fourier-transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy characterized the hybrid nanostructure used in the sensor surface modifier material. The hybrid nanostructure showed an excellent synergistic effect that contributed to the oxidation reaction of ceftriaxone. The screen-printed electrode modified with SiO2/ZrO2/Cdot-N nanostructure presented high sensitivity with a detection limit of 0.2 nmol L-1 in the linear range of 0.0078-40.02 μmol L-1. The measurements have been performed by square wave voltammetry technique. Studies on real samples of synthetic urine, urine, and tap water showed 95%-105% recovery without applying any sample pretreatment. The sensor demonstrated excellent selectivity in the antibiotic ceftriaxone determination in the presence of possible interferences cationic, Na+, K+, Ca2+, Mg2+, Cu2+, Pb2+, Mn2+, Zn2+, Co2+, and biological, glucose, caffeine, uric acid, and ascorbic acid. The developed sensor becomes a selective, sensitive, and applicable tool in determining the antibiotic ceftriaxone.

A lanthanide luminescent sensor for the detection of 4-nitrophenol in aqueous media

The development of facile luminescent sensors for detecting nitrophenols in aqueous media is of great necessity for the safety of the environment and human health, as they are a class of widespread toxic organic pollutants that cause serious adverse effects upon consumption. Based on a new multidentate asymmetric ligand (H2L) in which salicylamide and 4-nitryl-salicylaldimine are spaced by 1,2-bis(2-ethoxy)ethyl, a new hydrostable lanthanide intercycle, [Tb2L2(NO3)2]·CH3CN (Tb-[2]c), was prepared to act as a new luminescent sensor for 4-NP in water media. Structural analysis indicated that two fully deprotonated L2- ligands in cis-configuration and μ2-L-κ2O1:κO2:κO4:κN2:κO5 coordination mode were interlocked by two TbIII ions to render the emitted TbIII encapsulated by L2- for lessening non-radiative transitions. The excellent sensitizing capability of the ligand L2- to TbIII was ascertained by both experimental methods and theoretical calculations. The sensing exploration indicated that Tb-[2]c exhibited highly sensitive and selective recognition of 4-NP against other nitroaromatics in aqueous media. The recognition mechanism could be attributed to the internal filtration effect (IFE) mechanism when DFT calculations and accumulating experimental evidence were combined.

Electrochemical Detection of Flutamide by the Composite of Complex Based on Thiacalix[4]arene Derivatives and Reduced Graphene Oxide

In this paper, a thiacalix[4]arene complex [Zn2(TIT4A)L2]·4DMF·2CH3OH (H2L = 4,4'-oxybisbenzoic acid) (Zn-TIT4A-L) was synthesized by a solvothermal method. The composites were prepared by combining Zn-TIT4A-L with reduced graphene oxide (RGO), mesoporous carbon (MC), and multi-walled carbon nanotubes (MWCNTs), respectively. Three representative composites are Zn-TIT4A-L@RGO(1:1), Zn-TIT4A-L@MC(1:2), and Zn-TIT4A-L@MWCNT(1:2). X-ray diffraction and scanning electron microscopy characterized their structures and morphologies. The results showed that three composites were successfully prepared, and the crystals of the complex remained in the composites. The electrochemical properties of the composites were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The results indicated that they had good electrocatalytic activity and conductivity. Among them, Zn-TIT4A-L@RGO(1:1) had the best performance and was used for the quantitative detection of flutamide (FTA). The linear range of detection is 0.1-200 μM, and the limit of detection is 0.015 μM. At the same time, the sensor also had good reproducibility, anti-interference, and stability. The sensor was also used for the detection of FTA in lake water, human urine, and serum with a satisfactory recovery rate. The possible mechanism of electrochemical detection of FTA was also discussed.

Development of an electrochemical sensor based on ternary oxide SiO2/Al2O3/SnO2 modified with carbon black for direct determination of clothianidin in environmental and food samples

This study presents the development of an electrochemical sensor, denoted as GCE/CB/SiAlSn, based on the modification of a glassy carbon electrode surface with the ternary oxide SiO2/Al2O3/SnO2 associated with carbon black, for direct determination of the neonicotinoid pesticide clothianidin in different matrices, such as environmental and food samples. Morphological characterization by the scanning electron microscopy technique, electroanalytical analyses using the cyclic voltammetry technique and differential pulse voltammetry are presented which demonstrated that the developed electrochemical platform presents high sensitivity in the electroanalytical clothianidin determination. The linear range studied was from 2.99 × 10-7 to 6.04 × 10-5 mol L-1, with an LOD of 2.47 nmol L-1. This high sensitivity was explained using the synergistic relationship between carbon black and ternary oxide that maximized the electroactive surface area of the GCE/CB/SiAlSn sensor. Interferent studies were performed that showed high selectivity of the sensor to the pesticide in the presence of Ca2+, K+, Na+, and Mg2+ and carbendazim, glyphosate, imidacloprid and thiamethoxam pesticides. The sensor was applied to real samples of tap water and apple juice obtaining recoveries from 91.0% to 103.0%.

Cyclodextrin Inclusion Complexes and Their Application in Food Safety Analysis: Recent Developments and Future Prospects

Food safety issues are a major threat to public health and have attracted much attention. Therefore, exploring accurate, efficient, sensitive, and economical detection methods is necessary to ensure consumers' health. In this regard, cyclodextrins (CDs) are promising candidates because they are nontoxic and noncaloric. The main body of CDs is a ring structure with hydrophobic cavity and hydrophilic exterior wall. Due to the above characteristics, CDs can encapsulate small guest molecules into their cavities, enhance their stability, avoid agglomeration and oxidation, and, at the same time, interact through hydrogen bonding and electrostatic interactions. Additionally, they can selectively capture the target molecules to be detected and improve the sensitivity of food detection. This review highlights recent advances in CD inclusion technology in food safety analysis, covering various applications from small molecule and heavy metal sensing to amino acid and microbial sensing. Finally, challenges and prospects for CDs and their derivatives are presented. The current review can provide a reference and guidance for current research on CDs in the food industry and may inspire breakthroughs in this field.

Chemically Exfoliated Titanium Carbide MXene for Highly Sensitive Electrochemical Sensors for Detection of 4-Nitrophenols in Drinking Water

Soil and water contamination by numerous pollutants has been increasingly posing threats to food, water, agriculture, and human health. Using novel nanoscale materials to develop rapid electrochemical sensors is very promising due to the discovery of a number of new two-dimensional (2D) electronic materials. Of particular importance is 2D transition-metal carbide MXene that has been shown to possess transformative properties pertaining to its physical, chemical, and environmental characteristics, leading to their potential sensor applications. Designing electrochemical sensors using MXene has the potential to pave the way for monitoring environmental pollutants. Here, a stacked layer of chemically exfoliated MXene (Ti₃C₂T _x ) was demonstrated as an electrochemical sensor for detection of 4-nitrophenol (4-NP) with high sensitivity and a low limit of detection. Successful selective exfoliation of the MAX (Ti₃AlC₂) phase of the material by chemical etching without oxidation is shown to be the key to achieving higher sensitivity and a lower detection limit. In the optimal conditions, the proposed MXene sensor electrodes were capable of detecting 4-NP in a broad concentration range from 500 nM to 100 μM with a good linear sensing range (regression fit, R = 0.995). The higher sensitivity and notable limit of detection reached about 16.35 μA μM^-1 cm^-2 and 42 nM/L, respectively, with good reproducibility and repeatability. The real-time application of the proposed MXene sensor electrodes was confirmed by testing in tap water samples with excellent recoveries of 95-99%.

Carbon Black Functionalized with Naturally Occurring Compounds in Water Phase for Electrochemical Sensing of Antioxidant Compounds

A new sustainable route to nanodispersed and functionalized carbon black in water phase (W-CB) is proposed. The sonochemical strategy exploits ultrasounds to disaggregate the CB, while two selected functional naturally derived compounds, sodium cholate (SC) and rosmarinic acid (RA), act as stabilizing agents ensuring dispersibility in water adhering onto the CB nanoparticles’ surface. Strategically, the CB-RA compound is used to drive the AuNPs self-assembling at room temperature, resulting in a CB surface that is nanodecorated; further, this is achieved without the need for additional reagents. Electrochemical sensors based on the proposed nanomaterials are realized and characterized both morphologically and electrochemically. The W-CBs’ electroanalytical potential is proved in the anodic and cathodic window using caffeic acid (CF) and hydroquinone (HQ), two antioxidant compounds that are significant for food and the environment. For both antioxidants, repeatable (RSD ≤ 3.3%; n = 10) and reproducible (RSD ≤ 3.8%; n = 3) electroanalysis results were obtained, achieving nanomolar detection limits (CF: 29 nM; HQ: 44 nM). CF and HQ are successfully determined in food and environmental samples (recoveries 97–113%), and also in the presence of other phenolic classes and HQ structural isomers. The water dispersibility of the proposed materials can be an opportunity for (bio) sensor fabrication and sustainable device realization.

Electrochemical Sensing Systems for the Analysis of Catechol and Hydroquinone in the Aquatic Environments: A Critical Review

Because of their unique physical, chemical, and biological characteristics, conductive nanomaterials have a lot of potential for applications in materials science, energy storage, environmental science, biomedicine, sensors/biosensors, and other fields. Recent breakthroughs in the manufacture of carbon materials, conductive polymers, metals, and metal oxide nanoparticles based electrochemical sensors and biosensors for applications in environmental monitoring by detection of catechol (CC) and hydroquinone (HQ) are presented in this review. To achieve this goal, we first introduced recent works that discuss the effects of phenolic compounds and the need for accurate, inexpensive, and quick monitoring, and then we focused on the use of the most important applications of nanomaterials, such as carbon-based materials, metals, and metal oxides nanoparticles, and conductive polymers, to develop sensors to monitor catechol and hydroquinone. Finally, we identified challenges and limits in the field of sensors and biosensors, as well as possibilities and recommendations for developing the field for better future applications. Meanwhile, electrochemical sensors and biosensors for catechol and hydroquinone measurement and monitoring were highlighted and discussed particularly. This review, we feel, will aid in the promotion of nanomaterials for the development of innovative electrical sensors and nanodevices for environmental monitoring.

Ultrasonic assisted preparation of ultrafine Pd supported on NiFe-layered double hydroxides for p-nitrophenol degradation

NiFe-layered double hydroxide (NiFe-LDH)-loaded ultrafine Pd nanocatalysts (Pd/NiFe-LDHs) were prepared by a facile ultrasonic-assisted in situ reduction technology without any stabilizing agents or reducing agents. Pd/NiFe-LDHs were characterized by FT-IR, XRD, XPS, and TEM. PdNPs are uniformly dispersed on NiFe-LDHs with a particle size distribution of 0.77-2.06 nm and an average particle size of 1.43 nm. Hydroxyl groups in Fe-OH and Ni-OH were dissociated into hydrogen radicals (·H) excited by ultrasound, and ·H reduced Pd²⁺ to ultrafine PdNPs. Then, Pd was coordinated with O in Ni-O and Fe-O, which improved the stability of the catalysts. Pd/NiFe-LDHs completely degraded 4-NP in 5 min, and the TOF value was 597.66 h^-1, which was 16.7 times that of commercial Pd/C. The 4-NP conversion rate remained at 98.75% over Pd/NiFe-LDHs after 10 consecutive catalytic cycles. In addition, the catalyst also has high catalytic activity for the reduction of Congo red, methylene blue, and methyl orange by NaBH₄.

α-Hydroxy acids modified β-cyclodextrin capped iron nanocatalyst for rapid reduction of nitroaromatics: A sonochemical approach

This study reports a sonochemical approach for the synthesis and catalytic performance of zerovalent iron nanoparticles (nZVI) capped with two cyclodextrin (CD) crosslinked polymers derived from Lactic acid and Citric acid (CDLA and CDCA respectively). The polymers and the catalysts were characterized by NMR, FTIR, HRTEM, DLS, Zeta potential, FESEM, EDAX, VSM, XRD, XPS, TGA analysis. The catalysts proved to be sustainable and recyclable for rapid sonochemical reduction of nitroaromatics under ambient conditions. The isolated yield of the derivatives was found to be greater than 90%. The results suggest excellent dispersibility, stability, high iron content and smaller size of CDLA polymer capped nZVI compared to CDCA capped nZVI, leading to two-fold higher catalytic activity. The effect of various crucial catalysis parameters was investigated and optimized. The scope of the reaction was extended to other nitroaromatics under the optimized conditions. Being magnetically separable, the cost effective and non-toxic catalysts exhibited high recycling efficiency (~13 cycles), high turnover number (TON) and turnover frequency (TOF). The recyclable catalysts could be low-cost and sustainable options for organic transformation in water via sonochemical approach in aqueous medium.

Highly sensitive determination of anesthetic drug benzocaine based on hydroxypropyl-β-cyclodextrin-carbon black nanohybrids

Benzocaine (BZC) is a local anaesthetic drug coupled with numerous adverse effects, and thus poses a great challenge for its simple and highly sensitive detection. For resolving this issue, hydroxypropyl-β-cyclodextrin-carbon black (HP-β-CD-CB) nanohybrid that possesses the collaborative advantages of CB (e.g., excellent electrical properties, large surface area) and HP-β-CD (e.g., high molecule recognition and preconcentration capability) was synthesized in this study via a simple process and then utilized as a novel electrode material to electrochemically detect BZC. With the optimized experimental conditions, the HP-β-CD-CB nanohybrid-modified electrode shows wide linearity from 0.05 to 7.0 μM and very low detection limit (0.015 μM) for BZC detection. In addition, the repeatability, stability, and selectivity as well as practical-sample analysis of the HP-β-CD-CB electrode were investigated, and the observed results are desirable. The superior sensing performances coupled with its advantages including low-cost, simple and highly sensitive detection suggest that HP-β-CD-CB has important potential application for BZC analysis in practical samples.

Simple, low-cost and sensitive electrochemical sensing of antineoplastic drug amethopterin based on a nanocarbon black modified electrode

Various methods have been proposed currently to detect amethopterin (ATP, a widely used anticancer drug that is also called methotrexate); however, a simple and low-cost electrochemical method coupled with high sensitivity is scarce. In this study, by using low-cost and readily available nanocarbon black (NCB), which has excellent conductivity and stable dispersion in water as well as large surface area, as electrode materials to modify a glassy carbon electrode (GCE), a simple, inexpensive and highly-sensitive electrochemical sensor was constructed based on NCB/GCE. The electrochemical behaviors of ATP at both NCB/GCE and GCE were studied; the results show that the peak current of ATP at NCB/GCE is extremely higher than that at the bare GCE. For sensing ATP with high sensitivity, various control conditions including accumulation time, pH values of the phosphate buffer solution and NCB amount were optimized. The quantitative testing results show that NCB/GCE presents excellent sensing performances with a wide linearity range from 0.01 to 10.0 μM and low limit of detection (4.0 nM) towards ATP. Moreover, the investigation in the reproducibility and stability as well as selectivity of NCB/GCE demonstrated that the related results are also satisfactory. It is thus simple and effective method for ATP analysis and has important applications.

Pre-Anodized Graphite Pencil Electrode Coated with a Poly(Thionine) Film for Simultaneous Sensing of 3-Nitrophenol and 4-Nitrophenol in Environmental Water Samples

A very simple, as well as sensitive and selective, sensing protocol was developed on a pre-anodized graphite pencil electrode surface coated using poly(thionine) (APGE/PTH). The poly(thionine) coated graphite pencil was then used for simultaneous sensing of 3-nitrophenol (3-NP) and 4-nitrophenol (4-NP). The poly(thionine) coated electrode exhibited an enhanced electrocatalytic property towards nitrophenol (3-NP and 4-NP) reduction. Redox peak potential and current of both nitrophenols were found well resolved and their simultaneous analysis was studied. Under optimized experimental conditions, APGE/PTH showed a long linear concentration range from 20 to 230 nM and 15 nM to 280 nM with a calculated limit of detection (LOD) of 4.5 and 4 nM and a sensitivity of 22.45 µA/nM and 27.12 µA/nM for 3-NP and 4-NP, respectively. Real sample analysis using the prepared sensor was tested with different environmental water samples and the sensors exhibited excellent recovery results in the range from 98.16 to 103.43%. Finally, the sensor exposed an promising selectivity, stability, and reproducibility towards sensing of 3-NP and 4-NP.

β-Cyclodextrin-functionalized graphene and metal–organic framework composites for ultrasensitive electrochemical detection of chloramphenicol

Novel β-CD@functionalized graphene /Cu-BTC composites were in situ prepared using β-CD functionalized graphene and Cu-BTC, and a new electrochemical sensor for sensitive detection of chloramphenicol was developed based on the composites.

Free-electrodeposited anodic stripping voltammetry sensing of Cu(II) based on Ti3C2Tx MXene/carbon black

A proof-of-principle concept for free-electrodeposited anodic stripping voltammetry (ASV) sensing of Cu²⁺ is proposed by using Ti₃C₂T_x MXene/carbon black (Ti₃C₂T_x@CB) nanohybrids as electrode materials. Owing to the high adsorption and reduction capability of Ti₃C₂T_x towards Cu²⁺, Ti₃C₂T_x MXene enables Cu²⁺ to be immobilized and self-reduced directly to form Cu⁰ on the Ti₃C₂T_x@CB electrode surface. As a result an oxidation peak current appears from the re-oxidation of Cu⁰ via differential pulse voltammetry. Carbon black (CB) was introduced to prevent Ti₃C₂T_x Mxene aggregation and improve the related electron transfer as well as enhance their surface area. After optimizing various conditions, a considerable low limit of detection (4.6 nM) and a wide linear range (0.01-15.0 μM) for Cu²⁺ were achieved at the working potential from - 0.3 V to 0.0 V (vs SCE). Relative standard deviation (RSD) of eight individual Ti₃C₂T_x@CB electrodes is 3.72%, and the recoveries from tap water sample and lake water sample were in the ranges of 97.0-108% and 104-107%, respectively.

Polyvinylpyrrolidone-assisted solvent exfoliation of black phosphorus nanosheets and electrochemical sensing of p-nitrophenol

Few-layer black phosphorus (BP) has been considered as a rising star of 2D materials, and however, the poor stability heavily limits its application in electrochemical sensing. In this work, a series of BP nanosheets (BPNS) are simply prepared through ultrasonic exfoliation of bulk BP with the assistance of polyvinylpyrrolidone (PVP) in different solvents, including isopropanol (IPA), ethanol (EtOH), N-methyl pyrrolidone (NMP) and dimethylformamide (DMF). It is found that the exfoliation efficiency in IPA and EtOH is much higher than that in DMF and NMP, and moreover, IPA is superior than EtOH. More importantly, PVP effectively improves the exfoliation efficiency and ambient ability of BPNS via forming a protective layer to lower the oxidation of phosphorus. The exfoliated BPNS in the presence of IPA and PVP (PVP@BPNS) possess larger active response area, higher electron-transfer rate and stronger enhancement effects toward the oxidation of p-nitrophenol (4-NP). As a result, the response signal and sensing sensitivity of 4-NP are remarkably improved, and a novel electrochemical method has been developed for 4-NP detection, with a linear range of 0.10-5.0 μM and a detection limit of 28 nM. It is used to measure 4-NP in wastewater samples, and the results are validated by high-performance liquid chromatography.

A novel hybrid construction of MnMoO4 nanorods anchored graphene nanosheets; an efficient electrocatalyst for the picomolar detection of ecological pollutant ornidazole in water and urine samples

Nitroimidazole compounds are widely used antibiotics to encounter anaerobic bacterial and parasitic infections. The wide usage of antibiotic drugs became an ecological contaminant which in turn into potential monitoring. In this regards, we have designed and developed a new electrochemical sensing probe to monitor an antiprotozoal drug, ornidazole (ODZ), with the aid of a glassy carbon electrode (GCE) integrated with manganese molybdate nanorods (MnMoO4) decorated graphene nanosheets (GNS) hybrid materials that prepared by feasible probe sonochemical method (parameters: 2-4 W, 5 mV amp, 20 kHz). The electrochemical investigations of the developed probe were performed by using rapid scan electrochemical workstations namely cyclic voltammetry (CV) and amperometric (i-t) techniques. The as-prepared MnMoO4/GNS nanocomposite was characterized and its purity of nanocomposite formation was confirmed by various analytical techniques like X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. In addition to that, the textural morphology of the MnMoO4/GNS nanocomposite was examined with the aid of field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The MnMoO4/GNS nanocomposite rotating disk glassy carbon electrode (RDGCE) plays a crucial role in electrochemical detection of ODZ, which results in excellent anti-interference ability, a lower detection limit of 845 pM, massive linear ranges from 10 to 770 nM, and good sensitivity of about 104.62 μA μM-1 cm-2. From the acquired electrochemical studies, we have developed a disposable electrochemical sensor probe using a low-cost screen-printed carbon electrode (SPCE) with MnMoO4/GNS nanocomposite. The MnMoO4/GNS/SPCE are capably employed in real-time sensing of ODZ in water and urine samples. These electrochemical studies revealed the integral new vision on the electrocatalytic performance of the modified SPCE and also shown excellent amplification results in ultra-trace levels.

In situ formation of Co3O4 nanoparticles embedded N-doped porous carbon nanocomposite: a robust material for electrocatalytic detection of anticancer drug flutamide and supercapacitor application

The one-step synthesis of heteroatom-doped porous carbons is reported with the in situ formation of cobalt oxide nanoparticles for dual electrochemical applications (i.e., electrochemical sensor and supercapacitor). A single molecular template of zeolitic imidazole framework-67 (ZIF-67) was utilized for the solid-state synthesis of cobalt oxide nanoparticle-decorated nitrogen-doped porous carbon (Co₃O₄@NPC) nanocomposite through a facile calcination treatment. For the first time, Co₃O₄@NPC nanocomposite derived from ZIF-67 has been applied as an electrode material for the efficient electrochemical detection of anticancer drug flutamide (FLU). The cyclic voltammetry studies were performed in the operating potential from 0.15 to - 0.65 V (vs. Ag/AgCl). Interestingly, the fabricated drug sensor exhibited a very low reduction potential (- 0.42 V) compared to other  reported sensors. The fabricated sensor exhibited good analytical performance in terms of low detection limit (12 nM), wide linear range (0.5 to 400 μM), and appreciable recovery results (~ 98%, RSD 1.7% (n = 3)) in a human urine sample. Hereafter, we also examined the supercapacitor performance of the Co₃O₄@NPC-modified Ni foam in a 1M KOH electrolyte, and noticeable a specific capacitance of 525 F g^-1 at 1.5 A g^-1 was attained, with long-term cycling stability. The Co₃O₄@NPC nanocomposite supercapacitor experiments outperform the associated MOF-derived carbons and the Co₃O₄-based nanostructure-modified electrodes.

Visual recognition of ortho-xylene based on its host-guest crystalline self-assembly with α-cyclodextrin

HYPOTHESIS

Distinguishing substituted aromatic isomers is a challenging task because of the great similarity of their physicochemical properties. Considering xylene isomers have drastically different geometrical shapes, we predict this would show great impact on the self-assembling behavior of various xylene isomer@cyclodextrin inclusion complex.

EXPERIMENTS

Through host-guest crystalline self-assembly, among three isomers, only ortho-xylene is capable to form hydrogels with α-cyclodextrin. ROESY NMR, molecular simulations and circular dichroism spectra suggest that the ortho selectivity comes from the difference in the conformation of host-guest building block. The larger volume, and steric hinderance of the ortho isomer make it most possibly decrease their tendency to adopt more mobile orientations in cyclodextrin-based complex as meta and para isomers do, resulting in gel formation.

FINDINGS

Herein, we report a novel, facile and environmentally-friendly protocol on the recognition of ortho benzene isomers using α-cyclodextrin through host-guest crystalline self-assembly. Visual recognition of ortho-xylene is achieved through amplifying the structural difference of xylene isomers at molecular scale into macroscopic scale. We believe this work unveils subtle rules to control macroscopic assemblies at the molecular level and highlights the potential of using macrocyclic compounds to improve the quality and reduce the energy bill for separation in petrochemical industry.

da Silva Alves D, Okeke C, Breslin CB. Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.

Nanomolar level detection of non-steroidal antiandrogen drug flutamide based on ZnMn2O4 nanoparticles decorated porous reduced graphene oxide nanocomposite electrode

Flutamide is a non-steroidal antiandrogen drug and widely used in the treatment of prostatic carcinoma. Nevertheless, the excessive intake and improper disposal could affect the living organisms. In this work, we have synthesized a new nanocomposite based on ZnMn₂O₄ nanoparticles and porous reduced graphene oxide nanosheets (ZnMn₂O₄-PGO) for the electrocatalytic detection of flutamide (FLU) drug. The crystallinity and morphological properties of ZnMn₂O₄-PGO composite examined by different characterization techniques such as X-ray diffraction, Raman spectroscopy and so on. The fabricated ZnMn₂O₄-PGO nanocomposite modified electrode exhibited superior electrocatalytic performance to FLU drug in an optimized pH electrolyte. Fascinatingly, the electrode received a wide linear range (0.05-3.5 µM) with limit of detection of 8 nM. Besides, the developed ZnMn₂O₄-PGO nanocomposite electrode showed good sensitivity 1.05 µAµM^-1 cm^-2 and excellent selectivity for FLU detection in presence of various interfering species. A developed disposable electrode was scrutinized to determine FLU level in human urine samples by spiking method and the results achieved good recoveries in real sample analysis.

A molecularly imprinted poly 2-aminophenol-gold nanoparticle-reduced graphene oxide composite for electrochemical determination of flutamide in environmental and biological samples

A selective and sensitive electrochemical sensor based on reduced graphene oxide, gold nanoparticles, and molecularly imprinted poly 2-aminophenol was developed for electrochemical determination of flutamide in environmental and biological samples. The composite fabrication was electrochemically carried out and the composite was characterized by Fourier transform infrared, proton and carbon nuclear magnetic resonance, field emission scanning electron microscopy, and energy-dispersive X-ray spectrometry. The spectroscopic results showed that polymerization of molecularly imprinted poly 2-aminophenol took place through a ladder structure system. After optimization of effective parameters on the response of the sensor, the obtained linear range, relative standard deviation (for a concentration of 50 μg L^-1 with five replicates) and limit of quantification for flutamide determination were determined to be 2-375 μg L^-1, 1.54% and 0.8 μg L^-1, respectively. The results showed that the application of poly 2-aminophenol in the structure of the proposed sensor using a molecular imprinting approach made the sensor highly selective toward flutamide, distinguishing it from similar nitro-containing compounds. The prepared sensor was successfully utilized to analyze environmental water and urine samples. The obtained results showed that the proposed method is in agreement with the HPLC method and can be used as a reliable alternative method for the analysis of flutamide.

Fabrication of Co3O4 nanoparticle-decorated porous activated carbon electrode for the electrochemical detection of 4-nitrophenol

Preparation of Co3O4@BVFC for the electrochemical detection of 4-NP.

Sonochemical synthesis and fabrication of perovskite type calcium titanate interfacial nanostructure supported on graphene oxide sheets as a highly efficient electrocatalyst for electrochemical detection of chemotherapeutic drug

In green approaches for electrocatalyst synthesis, sonochemical methods play a powerful role in delivering the abundant surface areas and nano-crystalline properties that are advantageous to electrocatalytic detection. In this article, we proposed the sphere-like and perovskite type of bimetal oxides which are synthesized through an uncomplicated sonochemical procedure. As a yield, the novel calcium titanate (orthorhombic nature) nanoparticles (CaTiO₃ NPs) decorated graphene oxide sheets (GOS) were obtained through simple ultrasonic irradiation by a high-intensity ultrasonic probe (Titanium horn; 50 kHz and 60 W). The GOS/CaTiO₃ NC were characterized morphologically and chemically through the analytical methods (SEM, XRD, and EDS). Besides, as-prepared nanocomposites were modified on a GCE (glassy carbon electrode) and applied towards electrocatalytic and electrochemical sensing of chemotherapeutic drug flutamide (FD). Notably, FD is a crucial anticancer drug and also a non-steroidal anti-androgen chemical. Mainly, the designed and modified sensor has shown a wide linear range (0.015-1184 µM). A limit of detection was calculated as nanomolar level (5.7 nM) and sensitivity of the electrode is 1.073 μA μM^-1 cm^-2. The GOS/CaTiO₃ modified electrodes have been tested in human blood and urine samples towards anticancer drug detection.

Gold Nanoparticle Embedded on a Reduced Graphene Oxide/polypyrrole Nanocomposite: Voltammetric Sensing of Furazolidone and Flutamide

A new electrochemical sensor has been constructed based on the in situ preparation of gold nanoparticle embedded on reduced graphene oxide and polypyrrole nanotube (AuNP@rGO/PPyNT) composite through a nanosecond laser-induced heating technique. The as-prepared composite is used for individual as well as the simultaneous electrochemical determination of chemotherapy drug (furazolidone, FU) and anticancer drug (flutamide, FLT). The composite was analyzed by X-ray Diffraction, scanning electron microscopy/energy-dispersive X-ray analysis, transmission electron microscopy, Raman spectrometry, and X-ray photoelectron spectroscopy analysis, thus confirming the successful synthesis of this composite and its physical features. The modified AuNP@rGO/PPyNT electrode was examined through cyclic voltammetry and differential pulse voltammetry (DPV) methods in pH 7.0 for the determination of FU and FLT in individual, simultaneous, and mixed systems. The fabricated sensor showed wide linear responses (0.01-1080.11 μM and 0.01-1214.11 μM) of analytes, with the lower limits of detection of 2.3 and 2.45 nM and higher sensitivity of 53.75 and 50.06 μA μM^-1 cm^-2, respectively. Furthermore, the constructed sensor demonstrates higher stability, reproducibility, and repeatability, and is effectively applied for the analysis of FU and FLT content in the human serum sample analysis with satisfactory recovery.

Tin disulfide-graphene oxide-β-cyclodextrin mediated electro-oxidation of melatonin hormone: an efficient platform for electrochemical sensing

Here, we have developed an electrochemical sensor based on integrated 2D materials including tin disulfide (SnS2) nanoflakes, graphene oxide (GO), and β-cyclodextrin (β-CD) forming a ternary nanocomposite decorated on a screen-printed electrode (SPE) for the electrochemical detection of melatonin. Hydrothermally synthesized SnS2 was mixed with GO/β-CD to prepare the ternary composite via an ultra-sonication process. The nanocomposite was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and field emission transmission electron microscopy (FEG-TEM). The electrochemical performance of the modified electrode was investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The electrochemical sensor exhibited a linearity range from 1 nM to 100 μM with the lowest detection limit of 0.17 nM. The sensor was successfully applied for the detection of melatonin in commercial drugs and human saliva, which showed a consistent result with the Enzyme-Linked Immuno-Sorbent Assay (ELISA).