Benzidine Research Articles

Benzothioxanthene Dicarboximide as a Tuneable Electrogenerated Chemiluminescence Dye

AbstractOverlooked for years, the promising benzothioxanthene dicarboximide (BTXI) structure is nonetheless known to be an excellent fluorophore. As a further step towards the exploration of this rylene structure, the generation of electrochemiluminescence (ECL) in acetonitrile solutions is investigated herein as well as its direct comparison with a diphenylamine (DPA) derivative. Electrochemical characterization shows that the bare BTXI can be reversibly reduced or oxidized, characteristics which suggest the possibility that the electrogenerated reactive species can be exploited in the context of ECL. As a result, the BTXI moiety was found to be ECL‐active in both annihilation and co‐reactant mechanisms. Tri‐n‐propylamine (TPA) and benzoyl peroxide (BPO) were selected as sacrificial co‐reactants for promoting ECL. An ECL efficiency of 13 % (BTXI) and 6 % (BTXI‐DPA) compared to that of Ru(bpy)32+ was found when using TPA in oxidative ECL. Moreover, the ECL efficiency increased to 75 % and 55 % of Ru(bpy)32+ with BPO (i. e. reductive‐oxidation ECL) for BTXI and BTXI‐DPA, respectively. These results can be understood by calculating the free enthalpy of the redox reactions associated with each ECL pathway. Although the BTXI‐DPA red emitter exhibits more suitable thermodynamic properties, the BTXI green emitter is nonetheless more effective in combination with a co‐reactant due to a much larger photoluminescence quantum yield. The ECL spectra of the two molecules are compared to their photoluminescence spectra, revealing the involvement of the same excited states in the two different photoemission processes. In turn, the chemical engineering of BTXI is shown to be an effective platform for achieving tuneable ECL generation.

The Photoluminescence and Vibrational Properties of Black Phosphorous Sheets Chemically/Electrochemically Functionalized in the Presence of Diphenylamine.

In this work, new information concerning the optical properties of black phosphorus (BP) sheets chemically/electrochemically functionalized with diphenyl amine (DPA) and its macromolecular compound (poly(diphenylamine) (PDPA)) in the absence/presence of phosphotungstic acid (PTA) is reported. Raman scattering and FTIR spectroscopy studies indicate that the interaction of BP with PTA leads to the elimination of the PxOy layer onto the surface of the BP sheets. In the case of the chemical interaction of BP with DPA, the reaction product corresponds to DPA chemically functionalized BP sheets having an imino-phosphorane (IP) structure. The electrochemical oxidation of BP sheets chemically functionalized with DPA in the presence of PTA leads to an increase in the weight of P-N bonds as a consequence of the generation of PDPA doped with the PTA heteropolyanions, as shown by FTIR spectroscopy and Raman scattering. This process is evidenced by a shift of the Raman line from 362 cm-1 to 378 cm-1, assigned to the A1g mode. This change was explained by taking into account the compression of the layers containing P atoms, which is induced by PDPA macromolecular chains. The decrease in the intensity of the PL spectra of DPA as well as PDPA, in the presence of BP, indicates that BP acts as a PL quenching agent for these compounds. A preferential orientation of the PDPA doped with the PTA heteropolyanions on the surface of BP sheets is highlighted by the variation of the binding angle of the PDPA on the surface of BP sheets from 44.7° to 39.9°.

Buchwald–Hartwig coupled conjugated microporous polymer for efficient removal COVID-19 antiviral drug famciclovir from waters: Adsorption behavior and mechanism

The consumption of famciclovir (FCV) has been increased dramatically since the outbreak of coronavirus in 2019, and the pollution and harm of FCV in waters are concerned. Here, by utilizing aryl halides on 2, 4, 6-tris(4-bromophenyl)− 1, 3, 5-triazine (BPT) and primary amine groups on benzidine (BZ), a novel conjugated microporous polymer, namely BPT-BZ-CMP, was synthesized by Buchwald–Hartwig coupling reaction and applied in the removal of FCV from aqueous solution firstly. The synthesized BPT-BZ-CMP were characterized by various methods, including FTIR, SEM, BET, and Zeta–potential. Due to the micropore structure and high specific surface area, it took only 30 min for BPT-BZ-CMP to adsorb FCV to reach an equilibrium, and the maximum adsorption capacity was 347.8 mg·g−1. The Liu and pseudo-second-order kinetic models properly fit the adsorption equilibrium and kinetic data, respectively. The adsorption process was a spontaneous process, and the hydrogen bonding, π–π interaction and C–H···π interaction enhanced the adsorption of FCV on BPT-BZ-CMP. BPT-BZ-CMP maintained a good adsorption capacity after four consecutive adsorption–desorption cycle experiments. This study confirmed the potential of BPT-BZ-CMP as efficient sorbent to remove FCV from aqueous solutions.

Understanding the biological impact of organic pollutants absorbed by nanoplastics

Many organisms are consuming food contaminated with micro- and nanoparticles of plastics, some of which absorb persistent organic pollutants (POPs) from the environment and acting as carrier vectors for increasing the bioavailability in living organisms. We recently reported that polymethylmethacrylate (PMMA) nanoparticles at low concentrations are not toxic to animal models tested. In this study, the toxicity of diphenylamine (DPA) incorporated PMMA nanoparticles are assessed using barnacle larvae as a model organism. The absorption capacity of DPA from water for commercially available virgin PMMA microparticles is relatively low (0.14 wt%) during a 48 h period, which did not induce exposure toxicity to barnacle nauplii. Thus, PMMA nanoparticles encapsulated with high concentrations of DPA (DPA-enc-PMMA) were prepared through a reported precipitation method to achieve 40% loading of DPA inside the particles. Toxicity of DPA-enc-PMMA nanoparticles were tested using freshly spawned acorn barnacle nauplii. The observed mortality of nauplii from DPA-enc-PMMA exposure was compared to the values obtained from pure DPA exposure in water. The mortality among the exposed acorn barnacle nauplii did not exceed 50% even at a high concentration of DPA inside the PMMA nanoparticles. The results suggest that the slow release of pollutants from polymer nanoparticles may not induce significant toxicity to the organism living in a dynamic environment. The impact of long-term exposure of DPA absorbed plastic nanoparticles need to be investigated in the future.

An approach to detecting diphenylamine content and assessing chemical stability of single-base propellants by near-infrared reflectance spectroscopy

Diphenylamine (DPA) as a stabilizer component plays an important role in maintaining the chemical stability of single-base propellants (SBPs). This work investigated the feasibility of rapidly detecting the content of DPA in SBP by near-infrared reflectance spectroscopy (NIRS). The quantitative NIR model was developed by intervals selection, spectral pretreatment and factor number optimization. The optimal spectral intervals were determined to be 1081 nm ∼ 1280 nm and 1378 nm ∼ 1602 nm based on the characteristic spectral peaks of DPA. By comparing the performance of the developed models with different preprocessing methods, the best preprocessing method was standard normal variate transformation (SNV) + de-trending (Dr) + Smoothing. The optimal number of factors was 6 for DPA model. Partial least squares (PLS) regression was used to establish the calibration models of DPA. For the developed model, the determination coefficients of calibration and prediction (Rc2, Rp2) were 0.9907 and 0.9884, respectively. The root mean square errors of calibration and prediction (RMSEC, RMSEP) were 0.0310 and 0.0342, respectively. The samples in the prediction set were predicted by the developed model, and the average absolute error of the proposed and reference method was only 0.0265. The developed model can be applied in rapid monitor the content of DPA in SBP. In addition, vieille test have demonstrated that the chemical stability of SBP became worse with the decrease of DPA content. The content of DPA contained in the SBP with qualified chemical stability is not less than 0.8753%. Thus, the developed model can be used to judge whether the chemical stability of SBP is qualified or unqualified.

Planar D-σ-A type thermally activated delayed fluorescence material with Intra- and intermolecular charge transfer characteristics

Intramolecular charge transfer (intra-CT) and intermolecular charge transfer (inter-CT) are two general molecular design strategies of thermally activated delayed fluorescence (TADF) materials for organic light-emitting diodes (OLEDs). Herein, a diphenylamine (DPA) donor and a 2,4-diphenyl-1,3,5-triazine (TRZ) acceptor are connected by two planar units, non-conjugated 9,9-dimethyl-9H-xanthene (XA) and conjugated dibenzo[b,d]furan (FR), to give D-σ-A type emitter DPA-XA-TRZ and D-π-A type emitter DPA-FR-TRZ. Coexistence of intra- and inter-CT is found for DPA-XA-TRZ and is readily tuned by various doping concentrations owing to the non-conjugated linkage. In contrast, DPA-FR-TRZ shows a dominant intra-CT characteristic due to the strong molecular conjugation. The planar molecular skeleton of DPA-XA-TRZ could not only enhance intramolecular electronic coupling, but also reduce steric hindrance and shorten intermolecular distance to enhance inter-CT process. A maximum external quantum efficiency (EQEmax) of 21.9 % is achieved for the OLED device based on DPA-XA-TRZ, which is 2.5 times higher than that of DPA-FR-TRZ (8.4 %). DPA-XA-TRZ can also be utilized as an assistant host to sensitize multiple resonance TADF emitter DMAc-BN, and an EQEmax of 31.7 % is realized owing to its dual CT processes and high reverse intersystem crossing rate (kRISC), which is significantly superior to the conventional mCBP host and mCBP:PO-T2T exciplex cohost.

UV –Visible Spectroscopy Method Development and Its Validation for the Analysis of Marketed Hair Dyes for Amine Content

To develop a simple rapid, accurate and spectrophotometric reproducible method were developed for estimation of PARA - PHENYLENE DIAMINE in different Marketed Hair dyes . The analysis of PPD was performed using NaOH solution as diluent and using folins reagent at 432nm respectively .The methods were linear in the concentration range from 0-50µg/ml. The methods were validated with respect to system suitability, linearity, precision, limit of detection, limit of quantification, accuracy, ruggedness and robustness . The developed method can be used for routine analysis of PARA PHENYLENE DIAMINE in marketed hair products. The methods were validated in accordance to the ICH guidelines.

Effect of structural modifications on the spectral and lasing characteristics of truxene-cored starbursts with/without diphenylamine end-cappers

This study examined the effect of chemical modifications on the spectral and lasing characteristics of truxene-cored starbursts as gain media for organic lasers. A series of conjugated starburst materials, consisting of a truxene core and oligofluorene bridges with and without diphenylamine (DPA), namely, TrXD and TrX, were assessed as model molecules to investigate the influence of DPA on the photophysical characteristics and organic lasing behaviors. TrXD with DPA could effectively restrain the aggregation and greatly suppress the aggregation-induced emission quenching, yielding high photoluminescence efficiency. A higher radiative decay rate kr was observed for TrXD than for TrX, suggesting that DPA is beneficial for enhancing the radiative decay process. TrXD showed low amplified spontaneous emission thresholds of 2.1–4.3 μJ cm−2 with high net gain coefficients of 80–101 cm−1, rather low loss coefficients of 2.6–4.4 cm−1, compared with TrX. The best performance with a lasing threshold of 0.31 kW cm−2 was obtained for Tr3D, which was superior to that of Tr3 (0.86 kW cm−2). The molecular systems with DPA have a large potential as attractive molecules for organic lasers because of the superior lasing properties induced by kr.

Influence of organic ammonium derivatives on the equilibria between NH4+, NO2− and NO3− ions in the Nistru River water

The toxic effects of ammonium derivatives in the river water depend dramatically on their natural or synthetic origins and on their chemical structures. It has been proved that 1-naphtylamine (1-NA) and diphenylamine (DPA) breaking impact on the ammonium oxidation and especially on nitrite ions oxidation processes in natural waters is associated with its toxicity. The NH4+ oxidation process slows down for about five days and ten days in river water samples with 0.5 mg/L DPA and corresponding 0.5 mg/L 1-NA. The NO2− oxidation delay in model samples of river water with 0.025 and 0.05 mg/L 1-NA, is four days and 35 days in the one with 0.5 mg/L 1-NA. For the sample with 0.05 mg/L DPA the delay of the NO2− oxidation is approximately of six days and 25 days for sample with 0.5 mg/L, DPA. The laboratory simulations have revealed: (1) absorption–desorption, the micro biotic reaction to the instantaneous increase of the concentration of ammonium ion in the river water (so-called shock/stress effect) and (2) the NH4+ increase stimulated by a certain (0.05 mg/L) concentration of 1-NA.The diethylamine (DEA) decomposition leads to increasing with approximately 3.8 mg/L NH4+ in river water samples of 20.0 mg/L DEA.

Solar-light-driven ternary MgO/TiO2/g-C3N4 heterojunction photocatalyst with surface defects for dinitrobenzene pollutant reduction

Defect engineering and heterojunction are promising strategies to improve the photocatalytic performance of particular catalyst through effective charge carrier separation and transport. Herein, we developed Z-scheme MgO/TiO2/g-C3N4 ternary heterojunction photocatalyst with surface defects and effective charge separation for reduction of recalcitrant dinitrobenzene isomers under simulated solar light irradiation. Mott-Schottky (MS) plot analysis and electron spin resonance (ESR) radical trapping experiment suggested the formation of Z-scheme heterojunction at the interface of TiO2/g-C3N4, which played a crucial role in the electron-hole separation. Incorporating MgO into the structure further enhances charge separation via Ti3+ and oxygen vacancy (OV) defects formation at the TiO2/MgO interface as confirmed by electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses. Besides, the surface basicity of MgO enhanced conversion of dinitrobenzene (DNB) isomers through formation of nitrophenylhydroxylamine intermediate which can easily be reduced to phenylenediamines (PDAs). As confirmed by high performance liquid chromatography (HPLC) analysis, excellent selectivity for PDAs (95–98%) was achieved in 90 min with ternary MgO/TiO2/g-C3N4 composite compared to the binary MgO/TiO2 and TiO2/g-C3N4. A possible reaction pathway and photocatalytic reduction mechanism were proposed and elucidated. This work demonstrated an effective strategy to reduce recalcitrant dinitrobenzene isomers using efficient, low-cost, and environmental benign photocatalyst with a facile identification of reaction intermediates.

Toward understanding the regioselectivity of the one‐pot reaction of phenylene diamines with aldehydes and cyclopentadiene (Povarov reaction). Combined experimental and theoretical approaches

AbstractThree‐component acid‐catalyzed cyclocondensation of isomeric phenylenediamines with aldehydes and cyclopentadiene (CPD) was studied. In the M06‐2X//B3LYP/6–311 + G(d,p) + IEFPCM(SMD) approximation, a quantum chemical model was developed, energies of the PES stationary points were determined, and activation barriers were found for the CPD addition to the protonated Schiff base (rate‐limiting step) and for electrophilic carbocation cyclization to give endo, endo (syn)‐ or endo, exo (anti)‐cyclopentene‐annulated octahydropyridoquinoline‐ and octahydrophenanthroline‐based cycloadducts. The calculation results are in full agreement with the experimental data, which indicate that the cyclocondensation involving p‐phenylenediamine affords both types of cycloadducts, whereas the reactions of o‐ or m‐phenylenediamine lead to regioselective formation of octahydro‐1,10‐phenanthroline‐ or octahydropyridoquinoline‐based product, respectively. According to homo‐ and heteronuclear correlation 1Н and 13С NMR experiments and X‐ray diffraction data, the newly formed asymmetric centers of the cyclopentene‐annulated tetrahydroquinoline moiety in the polycyclic products have exo (endo)‐cis‐orientation.

Synthesis of copper nanoparticles on cellulosic fabrics and evaluation of their multifunctional performances

Two different kinds of copper nanoparticles (CuNPs) (brown colour and greenish colour) were synthesised by using simple solution route and applied by exhaust method to achieve multidimensional functionalization on one of the most popular cellulose materials e.g., cotton fabric. The synthesised CuNPs imparted different colours to the said textile due to different conditions of synthesis and localized surface plasmon resonance. Physico-chemical characterizations of the synthesized nanoparticles were performed by using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis whereas the optical properties of the nanoparticles were studied using UV–visible spectroscopy. The prepared CuNPs of both the types demonstrated very good antimicrobial activity up to 97%. In addition, cotton fabric treated with CuNPs showed very high catalytic activity for reduction of 4-nitroaniline (4-NA) in presence of sodium borohydride to phenylene diamine (4-PD). Washing durability and rubbing fastness of the treated fabric have also been measured by following standard testing methods and found to be very good with a rating 4.Graphical abstract

Fluorescent-tagged water with carbon dots derived from phenylenediamine as an equipment-free nanotracer for enhanced oil recovery

Chemical enhanced oil recovery (EOR) through waterflooding is the most commonly used method to improve crude oil displacement and extraction however; the impact of environmental side effects may remain ambiguous. Regarding, flooding tagged water with tracers provides a better understanding of the fate of injected water and the reservoir conditions more than oil recovery. This study's main focus is the proposed carbon dots (CDs) to develop fluorescent-tagged with dual functions as a sensing and an enhancing agent for EOR operations. Different physicochemical and optical properties were obtained for CDs by tuning the surface chemistry of phenylenediamine (PD) isomers and tartaric acid (TA) via the solvothermal method which leads to green, and yellow fluorescent emissions. Size distribution and colloidal and thermal stability of the prepared nanofluids carrying CDs were controlled by atomic force microscope (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, and thermogravimetric analysis (TGA). Long-time emission stability in high temperature and salinity such as conditions found in the oil reservoirs was precisely detected by fluorescence spectroscopy and a portable UV cabinet as the on-site detection method to confirm the sensing ability of CDs. While, rheological parameters of nanofluids such as viscosity, wettability alteration, and fluid/crude oil interfacial tension were evaluated to support the potential of CDs as an enhancing agent to sweep crude oil on the carbonate rock reservoirs. The oil displacement mechanism was monitored on the micromodel pattern by recording 27.8 % and 20.5 % displacement factors for the prepared nanofluids carrying 200 ppm CDs.

Polybenzoxazine/carbon nanotube nanocomposites as a polymeric sensing material for volatile organic compounds

The emissions of volatile organic compounds (VOCs) have hazardous effects on humans and the environment, and hence they should be detected and reduced. In this study, polybenzoxazine (PBZ) and amine-functionalized multiwall carbon nanotube (MWCNT) composites were synthesized as a sensor for VOCs. MWCNT were functionalized with two types of diamines, namely, 1,6-hexanediamine (HDA) and phenylenediamine (PDA). HDA or PDA treated MWCNTs were loaded into the benzoxazine matrix with different weight percentages (0.1, 0.3, 0.5, and 1%). FTIR analysis confirmed the chemical attachment of the two types of diamines on MWCNT. XRD diffraction and scanning electron microscopy (SEM) were used to investigate the nanofillers morphology and clarify the differences between pristine and amine-functionalized MWCNT. Thermal gravimetric analysis (TGA) was used to study the composites’ thermal stability and degradation behavior. It was found that, in contrast to neat PBZ, the major degradation temperature of PBZ/0.5%MWCNT-PDA nanocomposites were enhanced by 10%. The electrical conductivity of PBZ was 6.32 × 10–9, which was enhanced to 6.11 × 10–7 in the composites with 1% MWCNT-PDA. This material was tested as a VOCs sensor for methanol, acetone, and toluene and showed that PBZ/1% MWCNT-PDA composite responded to all the vapors.

A label-free electrochemical sensor constructed with layer-by-layer assembly of GCE-AuNPs-Q[7]·HAuCl4 for detection of diphenylamine.

Metal-organic frameworks (MOFs) including cucurbit[7]uril block (Q[7]·HAuCl4) were employed to develop a diphenylamine (DPA) sensor in electrochemical method, the presence of HAuCl4 improved the conductivity of the macrocyclic compound. To further enhance of the sensitivity, Au nanoparticles were inserted between the surface of glassy carbon electrode and Q[7]·HAuCl4 MOFs (GCE-AuNPs-Q[7]·HAuCl4). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were applied for evaluation on the electrochemical behavior. For the electrochemical inertness of DPA, a label-free electrochemical sensor in 5mM K3[Fe(CN)6] solution was achieved, to produce a limit of detection as low as 4.6µM in a linear range of 5-1000µM with good reproducibility, high stability and acceptable anti-interference ability. Application of the proposed electrode for the quantitative determination of DPA in tap water and apple juice confirms its real value.

A lead selective dimeric quinoline based fluorescent chemosensor and its applications in milk and honey samples, smartphone and bio-imaging

Dimeric quinoline-based Schiff base was developed (DQS) for the specific detection of Pb2+ ion via fluorimetry. DQS coordinates with Pb2+, a variation in fluorescence intensity with enhanced radical blue shift was observed due to the restriction of CN rotation, CN isomerization, and photoinduced electron transfer (PET) mechanisms. In addition, the intramolecular charge transfer (ICT) from electron-donating morpholine to phenylene diamine acceptor linked quinoline bridge is responsible for the blue-shifted fluorescence enhancement in the DQS-Pb2+ complex. The binding stoichiometry of DQS: Pb2+ (1:2) was confirmed by host–guest titration and mass spectrometry. The limit of detection (LOD) of the DQS was found to be 1.3 × 10-7 M for Pb2+ ion. The DQS sensing ability of Pb2+ was further applied into milk and honey samples, smartphone, bio-imaging and to construct of an INHIBIT molecular logic gate.

Structures and Photoluminescence Properties of Bis(aromatic amino)‐Based Isomers with Biphenyl as Bridge

Two groups of isomers based on the simple biphenyl were constructed for a deeper and better understanding of the relationships between the molecular structures and luminescent properties through the contrast of the crystal structures and the comprehensive analysis of theoretical calculations, which will have some catalytic effect for the researches on luminescent materials.

Transformation of Porous Organic Cages and Covalent Organic Frameworks with Efficient Iodine Vapor Capture Performance

The reaction of 5,5'-([2,2'-bipyridine]-5,5'-diyl)diisophthalaldehyde (BPDDP) with cyclohexanediamine and [benzidine (BZ)/[2,2'-bipyridine]-5,5'-diamine (BPDA)], respectively, affords a nitrogen-rich porous organic cage BPPOC and two two-dimensional (2D) covalent organic frameworks (COFs), USTB-1 and USTB-2 (USTB = University of Science and Technology Beijing), under suitable conditions. Interestingly, BPPOC with a single-crystal X-ray diffraction structure is able to successfully transform into USTB-1 and USTB-2 (newly converted COFs denoted as USTB-1c and USTB-2c, respectively) upon exchange of the imine unit of cyclohexanediamine in the cage by BZ and BPDA. Such a transformation also enables the isolation of analogous COFs (USTB-3c and USTB-4c) on the basis of an isostructural organic cage, BTPOC, which is derived from 5,5'-([2,2'-bithiophene]-4,4'-diyl)diisophthalaldehyde (BTDDP) and cyclohexanediamine. However, the conventional solvothermal reaction between BTDDP and BPDA leads to an impure phase of USTB-4 containing incompletely converted aldehyde groups due to the limited solubility of the building block. The newly prepared COFs have been characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. In particular, BPPOC is able to absorb the iodine vapor with an uptake of 5.64 g g-1, breaking the porous organic cage's (POC's) record value of 3.78 g g-1. Nevertheless, the cage-derived COFs exhibit improved iodine vapor adsorption capability in comparison with the directly synthesized counterparts, with the highest uptake of 5.80 g g-1 for USTB-1c. The mechanism investigation unveils the superiority of nitrogen atoms to sulfur atoms for POCs in iodine vapor capture with the assistance of definite crystal structures. This, in combination with porosity, synergistically influences the iodine vapor capture capacity of COFs.

Unraveling the origin of photoluminescence in dual emissive biogenic carbon dot

There has been considerable interest in dual emissive carbon quantum dots because of their exciting photoluminescence properties for varied applications. This work demonstrates a dual emissive system derived from a biogenic source, betalain extracted from beetroot. Different betalain carbon dots were prepared utilizing varying temperatures and time. The photoluminescence properties of BT−CD5160 (betalain carbon dots prepared at 160 ℃ for 5 min) and BT−CD10180 (betalain carbon dots prepared at 180 ℃ for 10 mins) were investigated in detail using photoluminescence (PL) spectroscopy and time-resolved PL decay studies. Interestingly the emission spectra are different and possess multi-emissive nature owing to the involvement of different surface states on the CDs. Further the PL response of BT−CD5160and, BT−CD10180in the presence of triethylamine (TEA), an aliphatic amine and, diphenylamine (DPA), an aromatic amine was found to be different when studied for both λext < 400 nm and > 400 nm. While the emission obtained from BT−CD5160 emerges from the aromatic carbon core and also from the functional groups attached to the carbon dots’ surface, the emission in BT−CD10180 is fully governed by the surface traps and defects obtained from the functionalities present. Hence, such investigated photoluminescence studies of the origin of emission will help exploit the dual emissive behaviour of biogenic carbon dots for extensive application in ratiometric sensing and optoelectronic devices.

Nanoarchitectured nickel phosphate integrated with graphene oxide for the toxicant diphenylamine detection in food samples

To date, numerous chemical substances are existing in food products, which cause some health issues in humans. Monitoring and controlling the level of toxicity in food for daily life is an important one. Hence, rapid and inexpensive detection methods are developed for the quantification of toxic chemicals. As a consequence, we have chosen the electrochemical sensing method for the detection of food toxicant diphenylamine (DPA). Herein, the flake-like structured nickel phosphate (NPO) is synthesized using the coprecipitation method and the preparation of NPO integrated graphene oxide (GO) by sonochemical treatment. As observed from electrochemical impedance spectra (EIS) analysis, the NPO/GO modified screen-printed carbon electrode (SPCE) has a lower charge transfer resistance (Rct) of 624 Ω and a fast electron transfer rate. The higher catalytic activity of NPO combined with a higher conductive and active surface area of GO through the electrostatic interaction is applied for the electrochemical determination of DPA. Using the differential pulse voltammetry (DPV) technique, the constructed NPO/GO/SPCE has a broad linear range (0.4 −680.8 μM), low LOD (12 nM), and good sensitivity (1.01 µA µM–1 cm–2) towards DPA sensing. Furthermore, the resultant sensor revealed good selectivity, cyclic and storage stability, repeatability, and reproducibility. The practical application of the DPA was estimated in food samples such as apple, grapes, and orange juice with satisfactory recovery.