Search Results (25)

Measuring pH with an optical sensor requires the immobilization of a chemical recognition phase on a solid surface. Neutral red (NR), an acid base indicator was used to develop two different optical probe configurations. The chemistry of aryl diazonium salts was chosen for the elaboration of this chemical phase, as it enables strong covalent bonds to be established on the surface of metallized glass or metallic surfaces. It also allows the formation of a thick film required to obtain an exploitable spectral response. The surfaces of interest (metallized optical fiber and 316 L stainless-steel mirror) are modelized by flat surfaces (metallized glass plates and 316 L stainless-steel plates). The analytical characterizations carried out (IR, XPS, UV-Visible, and profilometry) show that NR was covalently grafted onto the model surfaces as well as on the surfaces of interest. The supports grafted with NR to develop optical pH probes exhibit spectral changes, particularly the values of pKa, the pH range, and the isosbestic point wavelength. The experimental results show that the optical probe can be used for pH measurements between 4 and 8. Full article

The interfacial properties between carbon fiber (CF) and thermoplastic resin are relatively weak, which can be problematic for composites in structural applications. Improving the surface roughness of CF is regarded as an effective way to enhance the interface of composites. However, most CF modifying methods are complex and time-consuming, which cannot meet the demand for industrial production. Therefore, it is of great significance to research a fast technique of CF surface modification to strengthen the interface of composites. Herein, a one-pot reaction based on the aryl diazonium salt modification was applied to enhance the interface between CF and poly ether ether ketone (PEEK) resin. Carbon nanotubes (CNTs) were linked to CF by p-phenylenediamine (PPD) via cyclic voltammetry (CV). The surface morphology, chemical characteristics and surface energy of modified CF illustrated the effectiveness of this method, and the interfacial properties of as-prepared modified CF/PEEK demonstrated the increased tendency. All the CF was treated within 5 min and the interfacial shear strength (IFSS) of CF/PEEK was increased to the maximum of 99.62 MPa by aryl diazonium salt modification. This work may shed some light on the industrialized application of CF reinforced high-performance engineering thermoplastic composites. Full article

1-(3-aryl)-3-(dimethylamino)prop-2-en-1-one (enaminones) derivatives and the diazonium salt of para-chloroaniline were used to synthesize several novel disperse azo dyes with high yield and the use of an environmentally friendly approach. At 100 and 130 °C, we dyed polyester fabrics using the new synthesized disperse dyes. At various temperatures, the dyed fabrics’ color intensity was assessed. The results we obtained showed that dyeing utilizing a high temperature method at 130 °C was enhanced than dyeing utilizing a low temperature method at 100 °C. Reusing dye baths once or twice was a way to achieve two goals at the same time. The first was obtaining a dyed product at no cost, and the second was a way to treat the wastewater of dyeing bath effluents and reuse it again. Good results were obtained for the fastness characteristics of polyester dyed with disperse dyes. When the disperse dyes were tested against certain types of microbes and cancer cells, they demonstrated good and encouraging findings for the potential to be used as antioxidants and antimicrobial agents. Full article

An effective approach for the large-scale fabrication of conducting polyaniline (PANI) using in situ anodic electrochemical polymerization on nickel foam which had been coated in aryl diazonium salt (ADS)-modified graphene (ADS-G). In the present work, ADS-G was used as a high surface-area support material for the electrochemical polymerization of PANI. The electrochemical performances of the ADS-G/PANI composites exhibited better suitability as supercapacitor electrode materials than those of the PANI. The ADS-G/PANI composites achieved a specific capacitance of 528 F g⁻¹, which was higher than that of PANI (266 F g⁻¹) due to excellent electrode–electrolyte interaction and the synergistic effect of electrical conductivity between ADS-G and PANI in the composites. These findings suggest that the ADS-G/PANI composites are a suitable composite for potential supercapacitor applications. Full article

Hydroxyl radicals (•OH) are known as essential chemicals for cells to maintain their normal functions and defensive responses. However, a high concentration of •OH may cause oxidative stress-related diseases, such as cancer, inflammation, and cardiovascular disorders. Therefore, •OH can be used as a biomarker to detect the onset of these disorders at an early stage. Reduced glutathione (GSH), a well-known tripeptide for its antioxidant capacity against reactive oxygen species (ROS), was immobilized on a screen-printed carbon electrode (SPCE) to develop a real-time detection sensor with a high selectivity towards •OH. The signals produced by the interaction of the GSH-modified sensor and •OH were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV curve of the GSH-modified sensor in the Fenton reagent exhibited a pair of well-defined peaks, demonstrating the redox reaction of the electrochemical sensor and •OH. The sensor showed a linear relationship between the redox response and the concentration of •OH with a limit of detection (LOD) of 49 µM. Furthermore, using EIS studies, the proposed sensor demonstrated the capability of differentiating •OH from hydrogen peroxide (H₂O₂), a similar oxidizing chemical. After being immersed in the Fenton solution for 1 hr, redox peaks in the CV curve of the GSH-modified electrode disappeared, revealing that the immobilized GSH on the electrode was oxidized and turned to glutathione disulfide (GSSG). However, it was demonstrated that the oxidized GSH surface could be reversed back to the reduced state by reacting with a solution of glutathione reductase (GR) and nicotinamide adenine dinucleotide phosphate (NADPH), and possibly reused for •OH detection. Full article

The drug-resistance problem is widely spread and becoming more common in community-acquired and nosocomial strains of bacteria. Therefore, finding new antimicrobial agents remains an important drug target. From this perspective, new derivatives of benzothiazole were synthesized and evaluated for their antimicrobial activity and ability to inhibit the DHPS enzyme. The synthesis was carried out by the reaction of benzothiazole N-arylsulphonylhydrazone with N-aryl-2-cyano-3-(dimethylamino)acrylamide, N-aryl-3-(dimethylamino)prop-2-en-1-one, arylaldehydes or diazonium salt of arylamine derivatives, which led to the formation of N-arylsulfonylpyridones 6a–d (yield 60–70%) and 12a–c (yield 50–60%),N-(2-(benzo[d]thiazole-2-yl)-3-arylacryloyl-4-methylsulfonohydrazide 14a–c (yield 60–65%), 4-(benzo[d]thiazole-2-yl)-5-aryl-1H-pyrazol-3(2H)-one 16a–c (yield 65–75%), and N′-(2-(benzo[d]thiazol-2-yl)-2-(2-arylhydrazono)acetyl)-4-arylsulfonohydrazide 19a–e (yield 85–70%). The antimicrobial evaluations resulted into a variety of microbial activities against the tested strains. Most compounds showed antimicrobial activity against S. aureus with an MIC range of 0.025 to 2.609 mM. The most active compound, 16c, exhibited superior activity against the S. aureus strain with an of MIC 0.025 mM among all tested compounds, outperforming both standard drugs ampicillin and sulfadiazine. The physicochemical–pharmacokinetic properties of the synthesized compounds were studied, and it was discovered that some compounds do not violate rule of five and have good bioavailability and drug-likeness scores. The five antimicrobial potent compounds with good physicochemical–pharmacokinetic properties were then examined for their inhibition of DHPS enzyme. According to the finding, three compounds, 16a–c, had IC₅₀ values comparable to the standard drug and revealed that compound 16b was the most active compound with an IC₅₀ value of 7.85 μg/mL, which is comparable to that of sulfadiazine (standard drug) with an IC₅₀ value of 7.13 μg/mL. A docking study was performed to better understand the interaction of potent compounds with the binding sites of the DHPS enzyme, which revealed that compounds 16a–c are linked by two arene-H interactions with Lys220 within the PABA pocket. Full article

Eosin Y is one of the most popular organic dyes used as a photoredox catalyst and is largely employed in photochemical reactions both as a homogeneous and heterogeneous photocatalyst after immobilization. Immobilization of Eosin Y onto a solid support has many advantages, such as the possibility of recovery and reuse of the photocatalyst and the possibility of its use under flow conditions. In this paper, we report our findings on the immobilization of Eosin Y onto Merrifield resin and its application in the direct photochemical arylation of furan with aryldiazonium salts. The synthesized supported photocatalyst was used in batch reactions under heterogeneous conditions with different aryl diazonium salts, and its recovery and recycle were demonstrated for up to three times. The immobilized photocatalyst was then loaded in a packed-bed reactor and used under continuous flow conditions. The flow reaction allowed the arylated products to be obtained with higher productivity and space-time-yield than the batch in a very short reaction time. Full article

Arenediazonium o-benzenedisulfonimides have been used as efficient electrophilic partners in Cu(I) catalysed Ullmann-type coupling. The synthetic protocols are mild and easy, and produced either N-alkylanilines, aryl ethers, or thioethers in fairly good yields (18 positive examples, average yield 66%). o-Benzenedisulfonimide was recovered at the end of the reactions and was reused to prepare the starting salts for further reactions. It is noteworthy that diazonium salts have been used as electrophilic partners in the Ullmann-type protocol for the first time. Full article

In this paper, we propose an improved electrochemical platform based on graphene for the detection of DNA hybridization. Commercial screen-printed carbon electrodes (SPCEs) were used for this purpose due to their ease of functionalization and miniaturization opportunities. SPCEs were modified with reduced graphene oxide (RGO), offering a suitable surface for further functionalization. Therefore, aryl-carboxyl groups were integrated onto RGO-modified electrodes by electrochemical reduction of the corresponding diazonium salt to provide enough reaction sites for the covalent immobilization of amino-modified DNA probes. Our final goal was to determine the optimum conditions needed to fabricate a simple, label-free RGO-based electrochemical platform to detect the hybridization between two complementary single-stranded DNA molecules. Each modification step in the fabrication process was monitored by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using [Fe(CN)₆]^3−/4− as a redox reporter. Although, the diazonium electrografted layer displayed the expected blocking effect of the charge transfer, the next steps in the modification procedure resulted in enhanced electron transfer properties of the electrode interface. We suggest that the improvement in the charge transfer after the DNA hybridization process could be exploited as a prospective sensing feature. The morphological and structural characterization of the modified electrodes performed by scanning electron microscopy (SEM) and Raman spectroscopy, respectively, were used to validate different modification steps in the platform fabrication process. Full article

Transparent, flexible, biaxially oriented polyethylene terephthalate (PET) sheets were modified by bioactive polymer-fibronectin top layers for the attachment of cells and growth of muscle fibers. Towards this end, PET sheets were grafted with 4-(dimethylamino)phenyl (DMA) groups from the in situ generated diazonium cation precursor. The arylated sheets served as macro-hydrogen donors for benzophenone and the growth of poly(2-hydroxy ethyl methacrylate) (PHEMA) top layer by surface-confined free radical photopolymerization. The PET-PHEMA sheets were further grafted with fibronectin (FBN) through the 1,1-carbonyldiimidazole coupling procedure. The bioactive PET-PHEMA-I-FBN was then employed as a platform for the attachment, proliferation and differentiation of eukaryotic cells which after a few days gave remarkable muscle fibers, of ~120 µm length and ~45 µm thickness. We demonstrate that PET-PHEMA yields a fast growth of cells followed by muscle fibers of excellent levels of differentiation compared to pristine PET or standard microscope glass slides. The positive effect is exacerbated by crosslinking PHEMA chains with ethylene glycol dimethacrylate at initial HEMA/EGDA concentration ratio = 9/1. This works conclusively shows that in situ generated diazonium salts provide aryl layers for the efficient UV-induced grafting of biocompatible coating that beneficially serve as platform for cell attachment and growth of muscle fibers. Full article

Reproducible materials that have detection properties towards a certain molecule are very important for applications in the fabrication of devices. Among all the substrates that are used, highly oriented pyrolytic graphite allows to clearly image a monolayer. On the other hand, cryptand molecules are versatile because they can sense certain analytes with high selectivity. The highly oriented pyrolytic graphite electrode was first functionalized with an aryl bearing a bromine or an alkyne group to further attach cryptand molecules to its surface. The functionalization was performed through the electroreduction of aryl diazonium salts. While functionalization with an aryl-bromine produced a 20 nm-thick dendritic layer, functionalization of the surface with an aryl bearing a terminal alkyne produced a 9.7 nm-thick multilayer. However, if the diazonium salt is prepared in situ, a 0.9 nm monolayer with aryl–alkyne groups is formed. The alkyne functionalized electrode reacted with a bromo-cryptand through a Sonogashira C–C coupling reaction yielding electrodes functionalized with cryptands. These were immersed in a solution of a Co(II) salt resulting in Co(II)-cryptate modified electrodes, highlighting the ability of the cryptands’ modified electrode to sense metal ions. The electrode surface was analyzed by X-ray photoelectron spectroscopy after each modification step, which confirmed the successful functionalization of the substrate with both the cryptand and the cryptate. Cyclic voltammetry studies showed stable current response after approximately six cycles. Different reduction processes were detected for both cryptand (−1.40 V vs. SCE) and cryptate (−1.22 V vs. SCE) modified highly oriented pyrolytic graphite. Full article

Current selective modification methods, coupled with functionalization through organic or inorganic molecules, are crucial for designing and constructing custom-made molecular materials that act as electroactive interfaces. A versatile method for derivatizing surfaces is through an aryl diazonium salt reduction reaction (DSRR). A prominent feature of this strategy is that it can be carried out on various materials. Using the DSRR, we modified gold surface electrodes with 4-aminebenzene from 4-nitrobenzenediazonium tetrafluoroborate (NBTF), regulating the deposited mass of the aryl film to achieve covering control on the electrode surface. We got different degrees of covering: monolayer, intermediate, and multilayer. Afterwards, the ArNO₂ end groups were electrochemically reduced to ArNH₂ and functionalized with Fe(II)-Phthalocyanine to study the catalytic performance for the oxygen reduction reaction (ORR). The thickness of the electrode covering determines its response in front of ORR. Interestingly, the experimental results showed that an intermediate covering film presents a better electrocatalytic response for ORR, driving the reaction by a four-electron pathway. Full article

A biomimetic, ion-imprinted polymer (IIP) was prepared by electropolymerization of pyrrole at the surface of gold electrodes decorated with vertically grown ZnO nanorods. The vertical growth of the nanorods was achieved via an ultrathin aryl monolayer grafted by reduction of diazonium salt precursor. Pyrrole was polymerized in the presence of L-cysteine as chelating agent and Hg²⁺ (template). Hg²⁺-imprinted polypyrrole (PPy) was also prepared on a bare gold electrode in order to compare the two methods of sensor design (Au-ZnO-IIP vs. Au-IIP). Non-imprinted PPy was prepared in the same conditions but in the absence of any Hg²⁺ template. The strategy combining diazonium salt modification and ZnO nanorod decoration of gold electrodes permitted us to increase considerably the specific surface area and thus improve the sensor performance. The limit of detection (LOD) of the designed sensor was ~1 pM, the lowest value ever reported in the literature for gold electrode sensors. The dissociation constants between PPy and Hg²⁺ were estimated at [K_d1 = (7.89 ± 3.63) mM and K_d2 = (38.10 ± 9.22) pM]. The sensitivity of the designed sensor was found to be 0.692 ± 0.034 μA.pM^-1. The Au-ZnO-IIP was found to be highly selective towards Hg²⁺ compared to cadmium, lead and copper ions. This sensor design strategy could open up new horizons in monitoring toxic heavy metal ions in water and therefore contribute to enhancing environmental quality. Full article

The functionalization of carbon nanotubes (CNTs) plays a key role in their solubilization and compatibility for many applications. Among the many possible ways to functionalize CNTs, the creation of an Si–O–C bond is crucial for the formation of silicone composites. Catalyst-mediated silylesterification is useful in creating Si–O–C bonds because it is cost-effective and uses a hydrosilane precursor of lower reactivity than that of chlorosilane. However, it was previously demonstrated that two important silylesterification catalysts (zinc chloride and Karstedt’s catalyst) exhibit different selectivity for oxidized functional groups that are present on the surface of CNTs after oxidative acid treatment. This report details the selective modification of CNTs with various oxygenated functional groups (aromatic and nonaromatic alcohols, carboxylic acids, ethers, and ketones) using diazonium chemistry. Modified CNTs were used to assess the specifity of zinc chloride and Karstedt’s catalyst for oxygenated functional groups during a silylesterification reaction. Karstedt’s catalyst appeared to be widely applicable, allowing for the silylesterification of all of the aforementioned oxygenated functional groups. However, it showed lower efficacy for ethers and ketones. By contrast, zinc chloride was found to be very specific for nonaromatic carboxylic acids. This study also examined the Hansen solubility parameters of modified CNTs. Full article

A simple general synthesis of 1-aryl-6-azaisocytosine-5-carbonitriles 4 is described. This method is based on coupling diazonium salts with cyanoacetylcyanamide 2 and then cyclization of the formed 2-arylhydrazono-2-cyanoacetylcyanamides 3. The 6-azaisocytosines 4 were studied with respect to tautomeric equilibrium and the transformation of functional groups, and used in the synthesis of the condensed heterocyclic compounds: Purine isosteric imidazo[2,1-c]-[1,2,4]triazine 8 and the 1,2,4-triazino[2,3-a]quinazolines 9–12. Full article