The global attention has been focused on degradation of the environmental organic pollutants through green methods such as advanced oxidation processes (AOPs) under sunlight. However, AOPs have not yet been efficient in function of the photocatalyst that has been used. In this work, firstly, CaCu3Ti4O12 nanocomposite was simultaneously synthesized and decorated in different amounts of graphene oxide to enhance photodegradation of the organics. The result of the photocatalyst characterization showed that the sample with 8% graphene presented optimum photo-electrical properties such as low band gap energy and a great surface area. Secondly, the photocatalyst was applied for photodegradation of an organic model in a batch photoreactor. Thirdly, to scale up the process and optimize the efficiency, the photodegradation was modeled by multivariate semi-empirical methods. As the optimized condition showed, 45 mg/L of the methyl-orange has been removed at pH 5.8 by 0.96 g/L of the photocatalyst during 288 min of the light irradiation. Moreover, the photodegradation has been scaled up for industrial applications by determining the importance of the input effective variables according to the following organics order > photocatalyst > pH > irradiation time.
Hazardous industrial wastes negatively impact the environment by creating issues for aquatic as well as human's life. This study investigates the treatment of hazardous industrial wastewater using cost-effective graphite adsorbent along with electrochemical regeneration integrated with renewable solar energy. The synthetic industrial effluent containing crystal violet dye was treated using an adsorbent (Nyex™ 1000) having a surface area of 1.0 m2 g-1 . The efficiency of removing solute was found to be more than 90%. The adsorbent regeneration efficiency was achieved at 99.5% by passing a charge of 100 C g-1 at current density of 10 mA cm-2 for 1 h. Solar energy was integrated with electrochemical reactor for the regeneration of adsorbent to make the system cost-effective and self-sustainable. PRACTITIONER POINTS: Industrial hazardous wastewater treatment with a cost-effective graphite integrated adsorbent. Development of renewable solar energy-integrated with electrochemical system for regeneration. Regeneration efficiency of adsorbent Nyex™ 1000 was achieved around 99.5% with integrated system. Sustainable system was introduced to incorporate with renewable energy for waste water treatment.
This study investigated the electrochemical oxidation of stabilized leachate from Pulau Burung semi-aerobic sanitary landfill by conducting laboratory experiments with sodium sulfate Na(2)SO(4) (as electrolyte) and graphite carbon electrodes. The control parameters were influent COD, current density and reaction time, while the responses were BOD removal, COD removal, BOD:COD ratio, color and pH. Na(2)SO(4) concentration was 1 g/L. Experiments were conducted based on a three-level factorial design and response surface methodology (RSM) was used to analyze the results. The optimum conditions were obtained as 1414 mg/L influent COD concentration, 79.9 mA/cm(2) current density and 4 h reaction time. This resulted in 70% BOD removal, 68% COD removal, 84% color removal, 0.04 BOD/COD ratio and 9.1 pH. Electrochemical treatment using graphite carbon electrode was found to be effective in BOD, COD and color removal but was not effective in increasing the BOD/COD ratio or enhancing biodegradability of the leachate. The color intensity of the treated samples increased at low influent COD and high current density due to corrosion of electrode material.
The aim of this study was ultrasound assisted removal of Ceftriaxone sodium (CS) based on CCD model. Using sonochemical synthesized Bi2WO6 implanted on graphitic carbon nitride/Multiwall carbon nanotube (g-C3N4/MWCNT/Bi2WO6). For this purpose g-C3N4/MWCNT/Bi2WO6 was synthesized and characterized using diverse approaches including XRD, FE-SEM, XPS, EDS, HRTEM, FT-IR. Then, the contribution of conventional variables including pH, CS concentration, adsorbent dosage and ultrasound contact time were studied by central composite design (CCD) under response surface methodology (RSM). ANOVA was employed to the variable factors, and the most desirable operational conditions mass provided. Drug adsorption yield of 98.85% obtained under these defined conditions. Through conducting five experiments, the proper prediction of the optimum point were examined. The respective results showed that RSD% was lower than 5% while the t-test confirmed the high quality of fitting. Langmuir isotherm equation fits the experimental data best and the removal followed pseudo-second order kinetics. The estimation of the experimentally obtained maximum adsorption capacities was 19.57 mg.g- of g-C3N4/MWCNT/Bi2WO6 for CS. Boundary layer diffusion explained the mechanism of removal via intraparticle diffusion.
The main objective of this review is to derive the salient features of previously developed ultrasound-assisted methods for hydroxylating graphene and Buckminsterfullerene (C60). The pros and cons associated to ultrasound-assisted synthesis of hydroxy-carbon nanomaterials in designing the strategical methods for the industrial bulk production are also discussed. A guideline on the statistical methods has also been considered to further provide the scopes towards the application of the previously reported methods. Irrespective of many useful methods that have been developed in order to functionalize C60 and graphene by diverse oxygenated functional groups e.g. epoxide, hydroxyl, carboxyl as well as metal/metal oxide via a combination of organic chemistry and sonochemistry, there is no report dealing exclusively on the application of ultrasonic cavitation particularly to synthesising polyhydroxylated carbon nanomaterials. On this context, this review emphasizes in investigating the critical aspects of sono-nanochemistry and the statistical approaches to optimize the variables in the sonochemical process towards a large-scale synthesis of polyhydroxylated graphene and C60.
Graphene is one of the highly explored nanomaterials due to its unique and extraordinary properties. In this study, by utilizing a hydrothermal reduction method, graphene oxide (GO) was successfully converted to reduced graphene oxide (RGO) without using any toxic reducing agents. Following this, with the use of ultrasonic cavitation, profoundly stable few layer thick RGO nanodispersion was generated without employing any stabilizers or surfactants. During ultrasonication, shockwaves from the collapse of bubbles cause a higher dispersing energy to the graphene nanosheets which surpass the forces of Van der Waal's and π-π stacking and thus pave the way to form a stable aqueous nanodispersion of graphene. Ultrasonication systems with different power intensity have been employed to determine the optimum conditions for obtaining the most stable RGO dispersion. The optimised conditions of ultrasonic treatments led to the development of a very stable reduced graphene oxide (RGO) aqueous dispersion. The stability was observed for two years and was analyzed by using Zetasizer by measuring the particle size and zeta potential at regular intervals and found to have exceptional stability. The excellent stability at physiological pH promotes its utilization in nano drug delivery application as a carrier for Paclitaxel (Ptx), an anticancer drug. The in vitro cytotoxicity analysis of Ptx loaded RGO nanodispersion by MTT assay performed on the cell lines revealed the potential of the nanodispersion as a suitable drug carrier. Studies on normal lung cells, MRC-5 and nasopharyngeal cancer cells, HK-1 supported the biocompatibility of RGO-Ptx towards normal cell line. This investigation shows the potential of exceptionally stable RGO-Ptx nanodispersion in nano drug delivery applications.
This study investigates a prospective and straightforward method for producing graphene material derived from biomass, examining the influence of plant cell composition and functions. The experimental outcomes highlight ultrasound's crucial role in synthesizing graphene material sourced from biomass. Ultrasound, a pivotal element in the experiment, significantly affects graphene production from biomass by working synergistically with the liquid components in the solvent system. Notably, the ethanol content reduces the solution's surface tension, facilitating the effective dispersion of biochar and graphene oxide sheets throughout the process. Simultaneously, the water content maintains the solution's polarity, enhancing the cavitation effect induced by ultrasound. Biomass-derived graphene is exfoliated utilizing an ultrasonic bath system (134.4 W, 40 kHz, 0.5 W/cm2) from biochar. The as-synthesized graphene oxide exhibits a structure comprising a few layers while remaining intact, featuring abundant functional groups. Interestingly, the resulting product displays nanopores with an approximate diameter of 100 nm. These nanopores are attributed to preserving specific cell structures, particularly those with specialized cell wall structures or secondary metabolite deposits from biomass resources. The study's findings shed light on the impact of cellular structure on synthesizing graphene material sourced from biomass, emphasizing the potential application of ultrasound as a promising approach in graphene production.
This study aimed to assess the concentrations of cadmium (Cd), nickel (Ni) and lead (Pb) in the tissues of fish collected from the lower reach of the Kelantan River, Malaysia. Fishes were collected using gill nets during the dry and wet seasons. A total of 78 individual fish were caught and comprised 6 families, 11 genera and 13 species. The dorsal muscle was analysed using a graphite furnace Atomic Absorption Spectrometer (AAS). The mean concentration of Cd in Chitala chitala (0.076 mg/kg) was above the critical limit values of the European Commission (EC), World Health Organization (WHO) and Food and Agriculture Organization (FAO). The mean concentrations of Cd in Barbonymus gonionatus and Tachysurus maculatus were already at the level of concern, whereas the other species were approaching the limits of permissible levels. No fish samples were found to have a Ni level higher than the permissible limit of 0.5-0.6 mg/kg set by the WHO (1985). Osteochilus hasseltii (0.169 mg/kg) and T. maculatus (0.156 mg/kg) showed high Pb concentrations. The concentrations of heavy metals were found to be elevated in the wet season (p<0.05). Omnivorous fish were detected with elevated concentrations of Cd and Ni, whereas carnivorous fish had the highest concentration of Pb. The concentrations of Cd and Pb in fish tissues were positively correlated with fish weight (p<0.05). This study determined that the fish species caught in the Kelantan River were contaminated with non-essential metals (Cd, Ni and Pb). Nevertheless, the heavy metal concentration in the fish tissues, with the exception of C. chitala, O. hasseltii and T. maculatus, did not exceed the EC, FAO, Malaysian Food Act (MFA) or WHO guidelines.
A novel magnetic graphene oxide modified with chitosan (MGO-CTS) was synthesised as an adsorbent aimed to examine the simultaneous removal of mycotoxins. The composite was characterised by various procedures, namely Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and a scanning electron microscope (SEM). The adsorption evaluation was considered via pH effects, initial mycotoxin concentration, adsorption time and temperature. Adsorption isotherm data and kinetics experiments were acquired at the optimum pH 5 fit Freundlich isotherm as well as pseudo-second-order kinetic models. The thermodynamic results indicated that the adsorption of the mycotoxins was spontaneous, endothermic and favourable.
Toxicity effect of reduced graphene oxide (rGO) and titanium dioxide (TiO2) nanomaterials (NMs) on Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria was assessed. For both strains, study demonstrated that the toxicity was time and concentration dependent which led to reduction in growth rate and cell death. Upon NMs exposure, an instantaneous cell death in E. coli culture was observed. This is in contrast with B. subtilis, in which the culture growth remained in the log phase; however their growth rate constant,
μ g
was reduced by ∼70%. The discrepancy between E. coli and B. subtilis was due to strain-specific response upon contact with NMs. TEM, SEM and EDX analysis revealed direct physical surface-surface interaction, as evidence from the adherence of NMs on the cell surface.
Coal combustion and the disposal of combustion wastes emit enormous quantities of nano-sized particles that pose significant health concerns on exposure, particularly in unindustrialized countries. Samples of fresh and weathered class F fly ash were analysed through various techniques including X-ray fluorescence (XRF), X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), field-emission gun scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM) coupled with energy dispersive x-ray spectroscopy (EDS), and Raman Spectroscopy. The imaging techniques showed that the fresh and weathered coal fly ash nanoparticles (CFA-NPs) are mostly spherical shaped. The crystalline phases detected were quartz, mullite, ettringite, calcite, maghemite, hematite, gypsum, magnetite, clay residues, and sulphides. The most abundant crystalline phases were quartz mixed with Al-Fe-Si-K-Ti-O-amorphous phases whereas mullite was detected in several amorphous phases of Al, Fe, Ca, Si, O, K, Mg, Mn, and P. The analyses revealed that CFA-NPs are 5-500 nm in diameter and encapsulate several potentially hazardous elements (PHEs). The carbon species were detected as 5-50 nm carbon nanoballs of graphitic layers and massive fullerenes. Lastly, the aspects of health risks related to exposure to some detected ambient nanoparticles are also discussed.
The envelope glycoprotein domain III (EDIII) of dengue virus (DENV) has been recognised as the antigenic region responsible for receptor binding. In the present work, we have proposed a novel immunosensor constructed on a graphene-coated screen-printed carbon electrode (SPCE) using plant-derived EDIII as the probe antigen to target DENV IgG antibodies. The developed immunosensor demonstrated high sensitivity towards DENV IgG within a wide linear working range (125-2000 ng mL-1) under the optimised sensing conditions. The limit of detection was determined to be 22.5 ng mL-1. The immunosensor also showed high specificity towards DENV IgG, capable of differentiating DENV IgG from the antibodies of other infectious diseases including the similarly structured Zika virus (ZIKV). The ability of the immunosensor to detect dengue antibodies in serum samples was also verified by conducting tests on mouse serum samples. The proposed immunosensor was able to provide a binary (positive/negative) response towards the serum samples comparable to the conventional enzyme-linked immunosorbent assay (ELISA), indicating promising potential for realistic applications.
Surface enhanced Raman scattering (SERS) DNA biosensing is an ultrasensitive, selective, and rapid detection technique with the ability to produce molecule-specific distinct fingerprint spectra. It supersedes the long amplicon based PCR assays, the fluorescence and spectroscopic techniques with their quenching and narrow spectral bandwidth, and the electrochemical detection techniques using multiplexing. However, the performance of the SERS DNA biosensor relies on the DNA probe length, platform composition, both the presence and position of Raman tags and the chosen sensing strategy. In this context, we herein report a SERS biosensor based on dual nanoplatforms with a uniquely designed Raman tag (ATTO Rho6G) intercalated short-length DNA probe for the sensitive detection of the pig species Sus scrofa. In the design of the signal probe (SP), a Raman tag was incorporated adjacent to the spacer arm, followed by a terminal thiol modifier, which consequently had a strong influence on the SERS signal enhancement. The detection strategy involves the probe-target DNA hybridization mediated coupling of the two platforms, i.e., the graphene oxide-gold nanorod (GO-AuNR) functionalized capture probe (CP) and SP-conjugated gold nanoparticles (AuNPs), consequently enhancing the SERS intensity by both the electromagnetic hot spots generated at the junctions or interstices of the two platforms and the chemical enhancement between the AuNPs and the adsorbed intercalated Raman tag. This dual platform based SERS DNA biosensor exhibited outstanding sensitivity in detecting pork DNA with a limit of detection (LOD) of 100 aM validated with DNA extracted from a pork sample (LOD 1 fM). Moreover, the fabricated SERS biosensor showed outstanding selectivity and specificity for differentiating the DNA sequences of six closely related non-target species from the target DNA sequences with single and three nucleotide base-mismatches. Therefore, the developed short-length DNA linked dual platform based SERS biosensor could replace the less sensitive traditional methods of pork DNA detection and be adopted as a universal detection approach for the qualitative and quantitative detection of DNA from any source.
An effective electrode was developed based on electromembrane extraction (EME) and square wave voltammetry (SWV) for simultaneous separation, pre-concentration and determination of lead (II) (Pb(II)) ions in complex aqueous samples. Electrochemically reduced graphene oxide-graphite reinforced carbon (ErGO-GRC) was utilized in conjunction with the SWV. Pb(II) ions were extracted from an aqueous sample solution into an acidic acceptor phase (1M HCl) in the lumen of the polyvinylidene fluoride (PVDF) membrane bag by the application of voltage of maximum 6 V across the supported liquid membrane (SLM), consisting of organic solvent and di-(2-ethylhexyl)phosphoric acid (D2EHPA). The parameters affecting the EME were optimized for Pb(II) ions. The optimum EME conditions were found to be 20% D2EHPA in 1-octanol impregnated in the wall of PVDF membrane (PVDF17) as the SLM, extraction time of 20 min, pH of sample solution of 8 and a voltage of 5 V. The PVDF-ErGO-GRC electrode system attained enrichment factors of 40 times and 80% of extraction with relative standard deviations (n=5) of 8.3%. Good linearity ranging from 0.25 to 2 nM with coefficients correlation of 0.999 was obtained. The Pb(II) ions detection limit of PVDF-ErGO-GRC electrode was found to be 0.09 nM. The newly developed single setup electrochemical system was applied to complex aqueous samples such as tap, river and sea water to evaluate the feasibility of the method for applications.
A new poly(4-vinyl pyridine) (P4VP) based cadmium (Cd)-ion selective electrode (ISE) was developed. The 4-vinyl pyridine (4VP) was first polymerized electrochemically on the surface of graphite, later characterized by FTIR, SEM/EDX and then optimized as ISE for Cd. At optimal pH 6.4, slope of 27.7±0.8mVdecade(-1), linear concentration range of 1×10(-7) to 1.0×10(-1)M Cd(2+) and limit of detection (S/N=3) of 2.51×10(-8)M were obtained. The ISE was very selective towards Cd(2+), with K(pot)<1×10(-2) in the presence of the usual cations and anions in water samples. Response time and shelf life of less than 1min and 90 days, respectively, were observed. Its application was tested in various types of samples.
In this report, silver nanoparticles (Ag NPs) were successfully deposited on graphene oxide (GO) sheets to form GO-Ag nanocomposite using garlic extract and sunlight and the nanocomposite modified glassy carbon (GC) electrode was applied as an electrochemical sensor for the detection of nitrite ions. The formation of GO-Ag nanocomposite was confirmed by using UV-visible absorption spectroscopy, TEM, XRD and FTIR spectroscopy analyses. Further, TEM pictures showed a uniform distribution Ag on GO sheets with an average size of 19 nm. The nanocomposite modified electrode produced synergistic catalytic current in nitrite oxidation with a negative shift in overpotential. The limit of detection (LOD) values were found as 2.1 µM and 37 nM, respectively using linear sweep voltammetry (LSV) and amperometric i-t curve techniques. The proposed sensor was stable, reproducible, sensitive and selective toward the detection nitrite and could be applied for the detection of nitrite in real water sample.
In this study, a sensitive and cost-effective electrochemically reduced graphene oxide (ErGO) on graphite reinforced carbon (GRC) was developed for the detection of lead (Pb(II)) ions present in the real-life samples. A film of graphene oxide (GO) was drop-casted on GRC and their electrochemical properties were investigated using cyclic voltammetry (CV), amperometry and square wave voltammetry (SWV). Factors influencing the detection of Pb(II) ions, such as grades of GRC, constant applied cathodic potential (CACP), concentration of hydrochloric acid and drop-casting drying time were optimised. GO is irreversibly reduced in the range of -0.7 V to -1.6 V vs Ag/AgCl (3 M) in acidic condition. The results showed that the reduction behaviour of GO contributed to the high sensitivity of Pb(II) ions detection even at nanomolar level. The ErGO-GRC showed the detection limit of 0.5 nM and linear range of 3-15 nM in HCl (1 M). The developed electrode has potential to be a good candidate for the determination of Pb(II) ions in different aqueous system. The proposed method gives a good recovery rate of Pb(II) ions in real-life water samples such as tap water and river water.
Chrome azurol S immobilised on XAD-2 has been used in this study as a reagent phase for the development of an optical fibre Al(III) sensor. Using a kinetic approach, this sensor was able to give a linear response in the Al(III) concentration range of 1.3 x 10(-5)-2.0 x 10(-4) M with a limit of detection of 1.0 x 10(-4) M. The optimum responses were obtained at pH 6.0 and when the solution was stirred. The sensor response was found to have a repeatability and reproducibility of 1.6% and 5.8%, respectively. The results obtained for Al(III) determination in aqueous sample were in good agreement with those obtained using graphite furnace-atomic absorption spectrometry.
Surface plasmon resonance (SPR) is a label-free optical spectroscopy that is widely used for biomolecular interaction analysis. In this work, SPR was used to characterize the binding properties of highly sensitive nanocrystalline cellulose-graphene oxide based nanocomposite (CTA-NCC/GO) towards nickel ion. The formation of CTA-NCC/GO nanocomposite has been confirmed by FT-IR. The SPR analysis result shows that the CTA-NCC/GO has high binding affinity towards Ni2+ from 0.01 until 0.1 ppm with binding affinity constant of 1.620 × 103 M-1. The sensitivity for the CTA-NCC/GO calculated was 1.509° ppm-1. The full width at half maximum (FWHM), data accuracy (DA), and signal-to-noise ratio (SNR) have also been determined using the obtained SPR curve. For the FWHM, the value was 2.25° at 0.01 until 0.08 ppm and decreases to 2.12° at 0.1 until 10 ppm. The DA for the SPR curves is the highest at 0.01 until 0.08 ppm and lowest at 0.1 until 10 ppm. The SNR curves mirrors the curves of SPR angle shift where the SNR increases with the Ni2+ concentrations. For the selectivity test, the CTA-NCC/GO has the abilities to differentiate Ni2+ in the mixture of metal ions.
Due to the crucial role of dopamine (DA) in health and peripheral nervous systems, it is particularly important to develop an efficient and accurate sensor to monitor and determine DA concentrations for diagnostic purposes and diseases prevention. Up to now, using surface plasmon resonance (SPR) sensors in DA determination is very limited and its application still at the primary stage. In this work, a simple and ultra-sensitive SPR sensor was constructed for DA detection by preparation of chitosan- graphene quantum dots (CS-GQDs) thin film as the sensing layer. Other SPR measurements were conducted using different sensing layers; GQDs, CS for comparison. The proposed thin films were prepared by spin coating technique. The developed CS-GQDs thin film-based SPR sensor was successfully tested in DA concentration range from 0 fM to 1 pM. The designed SPR sensor showed outstanding performance in detecting DA sensitively (S = 0.011°/fM, R2 = 0.8174) with low detection limit of 1.0 fM has been achieved for the first time. The increased angular shift of SPR dip, narrow full width half maximum of the SPR curves, excellent signal-to-noise ratio and figure of merit, and a binding affinity constant (KA) of 2.962 PM-1 demonstrated the potential of this sensor to detect DA with high accuracy. Overall, it was concluded that the proposed sensor would serve as a valuable tool in clinical diagnostic for the serious neurological disorders. This in turns has a significant socio-economic impact.