Synthesis and characterization of polyaniline-graphene quantum dot and the potential for pyrene detection using photoluminescence spectroscopy

Detection of Pyrene as a toxic material is vital to possess a healthy, non-polluted and well sustainable environment since Pyrene is highly toxic and ubiquitous and is of environmental concern due to its adverse health effects. Several methods currently measure Pyrene concentration, divided into analytical and nanomaterial-based sensors/sensing. Although analytical methods are accurate and give reliable measurements, they are costly, require more extended preparation, heavy equipment, qualified operators, and a large volume of solvent in separation and extraction procedures. Moreover, nanomaterials-based sensors/sensing, particularly semiconductor quantum dots (SQDs), is ultra-sensitive, fast, and easy; however, the most significant issue related to SQDs-based probes is that there is worry regarding cadmium used in the core, which can potentially leach and further contaminate the environment after discarding the probes. Therefore, there is a need to develop a novel method which includes proper materials with a low limit of detection (LOD), cost-effective, easy, fast, simple, and user-friendly to overcome all those challenges. In this research, polyaniline-graphene quantum dot (PANI-GQD) nanocomposite films were prepared in different GQD concentrations (100 - 500) ppm by the chemical methods as a fluorescence nanomaterial, simple, sensitive, low cost and novel sensing element for the detection of Pyrene via photoluminescence (PL) spectroscopy. Before nanocomposite film preparation, PANI film was optimised using different acidic medium/dopant types (PTSA, CSA, Acetic acid, and HCl), PTSA concentrations (0.5% - 6%) selected acidic medium/dopants, and NMP concentrations (0.5% - 6%) as solvent. PANI and PANI-GQD nanocomposite films were characterized and evaluated using FT-IR, UV-vis, XRD, FE-SEM, EDS, TGA, four-point probe, and PL spectroscopy. The 1% toluene-4-sulfonic acid monohydrate and 3% N-Methyl-2-pyrrolidone doped PANI was introduced as optimized PANI film with a high conductivity value of 2.45 (Ω cm)-1, high PL intensity (excitation: 77334, emission: 37650), and low bandgap value of 2.54 (eV) due to orderly organized benzenoid and quinoid parts in its structure. In PANI-GQD nanocomposite films, the carboxylic acid groups of GQD are well-doped optimized PANI films characterized by FT-IR and UV-vis. The morphology of the PANI-GQD nanocomposites exhibited a change from nanoflakes to nonspherical with increasing GQD concentration. The PANI-GQD in 300 ppm of GQD concentration was introduced as the optimized PANI-GQD nanocomposite film with a high conductivity value of 2.28 (Ω cm)-1, high PL intensity (excitation: 231982, emission: 161435) and low bandgap value of 2.39 (eV). The PL results revealed the interaction of optimized PANI and PANI-GQD nanocomposite films with Pyrene. The LOD for Pyrene was calculated at 6.61 and 0.40 × 10-9 mol L-1 (S/N = 5) in the linear range of (0.001 - 10) × 10-9 mol L-1 based on optimized PANI and optimized PANI-GQD nanocomposite films, respectively. Furthermore, the PANI-GQD nanocomposite film showed the lowest LOD of Pyrene. The obtained LOD was comparable with WHO standards and specifications for Pyrene, which is 3.461 × 10-9 mol L-1 (0.7 µg/l) in the environment. Thus, this study proposes PANI-GQD nanocomposite film as a novel sensing element for detecting Pyrene

Polyaniline Synthesized by Different Dopants for Fluorene Detection via Photoluminescence Spectroscopy

The effects of different dopants on the synthesis, optical, electrical and thermal features of polyaniline were investigated. Polyaniline (PANI) doped with p-toluene sulfonic acid (PANI-PTSA), camphor sulphonic acid (PANI-CSA), acetic acid (PANI-acetic acid) and hydrochloric acid (PANI-HCl) was synthesized through the oxidative chemical polymerization of aniline under acidic conditions at ambient temperature. Fourier transform infrared light, X-ray diffraction, UV-visible spectroscopy, field emission scanning electron microscopy, photoluminescence spectroscopy and electrical analysis were used to define physical and structural features, bandgap values, electrical conductivity and type and degree of doping, respectively. Tauc calculation reveals the optical band gaps of PANI-PTSA, PANI-CSA, PANI-acetic acid and PANI-HCl at 3.1, 3.5, 3.6 and 3.9 eV, respectively. With the increase in dopant size, crystallinity is reduced, and interchain separations and d-spacing are strengthened. The estimated conductivity values of PANI-PTSA, PANI-CSA, PANI-acetic acid and PANI-HCl are 3.84 × 101, 2.92 × 101, 2.50 × 10−2, and 2.44 × 10−2 S·cm−1, respectively. Particularly, PANI-PTSA shows high PL intensity because of its orderly arranged benzenoid and quinoid units. Owing to its excellent synthesis, low bandgap, high photoluminescence intensity and high electrical features, PANI-PTSA is a suitable candidate to improve PANI properties and electron provider for fluorene-detecting sensors with a linear range of 0.001–10 μM and detection limit of 0.26 nM

Enhancement of the fluorescence property of carbon quantum dots based on laser ablated gold nanoparticles to evaluate pyrene

Gold nanoparticles were prepared in a carbon quantum dots solution using the laser ablation technique to enhance the photoluminescence property of a carbon quantum dots solution. The gold plate was ablated using a Q-Switched Nd:YAG laser at 4, 8, 12, and 16 minutes with a stable laser energy. The optical properties, functional groups, and the morphology of the prepared samples were examined using UV-visible spectroscopy, Fourier transform spectroscopy, and transmission electron microscopy, respectively. When the ablation time increased, the size of the gold nanoparticles decreased from 20.69 nm to 13.52 and the plasmonic quality factor and concentration of the gold nanoparticles increased. The intensity peak of the photoluminescence carbon quantum dots solution increased in the presence of the gold nanoparticles and the interaction between the pure carbon quantum dots and the gold-nanoparticles/carbon quantum dots composite with pyrene were investigated using photoluminescence spectroscopy. Consequently, the variation in the photoluminescent peak in the presence of the gold nanoparticles was greater than the variation in the photoluminescence peak in the presence of pure carbon quantum dots. The detection limit was 1 ppm. Therefore, the gold nanoparticles not only enhanced the photoluminescence property of the CQD bath also it improved the interaction of the CQD with pyrene

Glycerol-based retrievable heterogeneous catalysts for single-pot esterification of palm fatty acid distillate to biodiesel

The by-product of the previous transesterification, glycerol was utilised as an acid catalyst precursor for biodiesel production. The crude glycerol was treated through the sulfonation method with sulfuric acid and chlorosulfonic acid in a reflux batch reactor giving solid glycerol-SO3H and glycerol-ClSO3H, respectively. The synthesised acidic glycerol catalysts were characterised by various analytical techniques such as thermalgravimetric analyser (TGA), infrared spectroscopy, surface properties adsorption-desorption by nitrogen gas, ammonia-temperature programmed desorption (NH3-TPD), X-ray diffraction spectroscopy (XRD), elemental composition analysis by energy dispersive spectrometer (EDX) and surface micrographic morphologies by field emission electron microscope (FESEM). Both glycerol-SO3H and glycerol-ClSO3H samples exhibited mesoporous structures with a low surface area of 8.85 mm2/g and 4.71 mm2/g, respectively, supported by the microscopic image of blockage pores. However, the acidity strength for both catalysts was recorded at 3.43 mmol/g and 3.96 mmol/g, which is sufficient for catalysing PFAD biodiesel at the highest yield. The catalytic esterification was optimised at 96.7% and 98.2% with 3 wt.% of catalyst loading, 18:1 of methanol-PFAD molar ratio, 120 °C, and 4 h of reaction. Catalyst reusability was sustained up to 3 reaction cycles due to catalyst deactivation, and the insight investigation of spent catalysts was also performed

Plasmonic Biosensors for the Detection of Lung Cancer Biomarkers: A Review

International audienceLung cancer is the most common and deadliest cancer type globally. Its early diagnosis can guarantee a five-year survival rate. Unfortunately, application of the available diagnosis methods such as computed tomography, chest radiograph, magnetic resonance imaging (MRI), ultrasound, low-dose CT scan, bone scans, positron emission tomography (PET), and biopsy is hindered due to one or more problems, such as phenotypic properties of tumours that prevent early detection, invasiveness, expensiveness, and time consumption. Detection of lung cancer biomarkers using a biosensor is reported to solve the problems. Among biosensors, optical biosensors attract greater attention due to being ultra-sensitive, free from electromagnetic interference, capable of wide dynamic range detection, free from the requirement of a reference electrode, free from electrical hazards, highly stable, capable of multiplexing detection, and having the potential for more information content than electrical transducers. Inspired by promising features of plasmonic sensors, including surface plasmon resonance (SPR), localised surface plasmon resonance (LSPR), and surface enhanced Raman scattering (SERS) such as ultra-sensitivity, single particle/molecular level detection capability, multiplexing capability, photostability, real-time measurement, label-free measurement, room temperature operation, naked-eye readability, and the ease of miniaturisation without sophisticated sensor chip fabrication and instrumentation, numerous plasmonic sensors for the detection of lung cancer biomarkers have been investigated. In this review, the principle plasmonic sensor is explained. In addition, novel strategies and modifications adopted for the detection of lung cancer biomarkers such as miRNA, carcinoembryonic antigen (CEA), cytokeratins, and volatile organic compounds (VOCs) using plasmonic sensors are also reported. Furthermore, the challenges and prospects of the plasmonic biosensors for the detection of lung cancer biomarkers are highlighted