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In the present study, iminodiacetic acid (IDA)-modified kenaf fiber, K-IDA formed by the chemical modification of plant kenaf biomass was tested for its efficacy as a sorbent material towards the purification of waste water. The K-IDA fiber was first characterized by the instrumental techniques like Fourier transform infrared (FTIR) analysis, elemental analysis (CHNSO), and scanning electron microscopy (SEM). On testing for the biosorption, we found that the K-IDA has an increment in the adsorption of Cu 2+ ions as compared against the untreated fiber. The Cu 2+ ions adsorption onto K-IDA fits very well with the Langmuir model and the adsorption maximum achieved to be 91.74 mg/g. Further, the adsorption kinetics observed to be pseudo second-order kinetics model and the Cu 2+ ions adsorption is a spontaneous endothermic process. The desorption study indicates a highest percentage of Cu 2+ of 97.59% from K-IDA under 1 M HCl solution against H 2 SO 4 (72.59%) and HNO 3 (68.66%). The reusability study indicates that the efficiency did not change much until the 4th cycle and also providing enough evidence for the engagement of our biodegradable K-IDA fiber towards the removal of Cu 2+ ions in real-time waste water samples obtained from the electroplating and wood treatment industries. [ABSTRACT FROM AUTHOR]

This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0–178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4 °C in silica gel. [ABSTRACT FROM AUTHOR]

Abstract: A new electrochemical biosensor is described for voltammetric detection of gene sequence related to Trichoderma harzianum. The sensor involves immobilization of a 20 base single-stranded probe (ssDNA), which is complementary to a specific gene sequence related to T. harzianum on a gold electrode through specific adsorption. The DNA probe was used to determine the amount of target gene in solution using methylene blue (MB) as the electrochemical indicator. The covalently immobilized probe could selectively hybridize with the target DNA to form a hybrid on the surface despite the bases being attached to the electrode. The changes in the peak currents of methylene blue (MB), an electroactive label, were observed upon hybridization of probe with the target. Peak currents were found to increase in the following order: hybrid-modified AuE and the probe-modified AuE which localized to the affinity of MB. Control experiments with the non-complementary oligonucleotides were performed to assess whether the DNA biosensor responds selectively, via hybridization, to the target. DNA biosensor also able to detect microorganism at the species levels without nucleic acid amplification. The redox current was linearly related to the concentration of target oligonucleotide DNA, ranged from 1–20ppm. Numerous factors, affecting the probe immobilization, target hybridization and indicator binding reactions are optimized to maximize the sensitivity and reduce the assay time. [Copyright &y& Elsevier]

Abstract: Fatty hydroxamic acid (FHA) immobilized in polymethylmethacrylate (PMMA) has been studied as a sensor for V(V). Based on this sensing material, the response towards the different concentration of V(V) was found to be linear in the logarithmic concentration range of 0–2.3 (i.e. 1.0–200mgL−1). The detection limit was 0.7mgL−1. The relative standard deviation (R.S.D.) of reproducibility was 9.3 and 7.1% for V(V) at concentration of 50 and 200mgL−1, respectively. Interference from foreign ions was also studied at a molar ratio of V(V):foreign ions=1:1. It was found that Fe(III) ion interfered most seriously in the determination of V(V). The experimental result was found to be in good agreement with those obtained using the ICP-AES method. [Copyright &y& Elsevier]

Gallocynin immobilized in chitosan membrane has been studied as a sensor element of an optical sensor for lead using a flowing system. By using this set up, lead in solution has been determined in the concentration range from 1.0×10−1 to 1.0×103 ppm with a detection limit of 0.075 ppm. The standard deviation of the method for the repeatability of lead detection at a concentration of 100 ppm was found to be 2.10%. The response of the sensor was reproducible and can be regenerated by using acidified saturated KNO3 solution. Interference from foreign ions was also studied at 1:1 mole ratio of Pb(II):foreign ions. [Copyright &y& Elsevier]

In this study, the ionophore doped graphene-based bionanocomposite solution has been prepared using valinomycin, graphene oxide and chitosan in acetic acid under mild condition. After the reaction, the ionophore doped graphene-based bionanocomposite thin film was fabricated using spin coating technique. The structural and optical properties of the bionanocomposite thin film was characterized by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and ultraviolet-visible near infra-red (UV–vis-NIR). The functional group of the thin film has been confirmed by FTIR and surface morphology by AFM indicated that the bionanocomposite thin film is relatively smooth and homogeneous. The UV–vis-NIR analysis showed that absorption of the thin film is high with optical band gap of 3.987 eV. Also, this derivative bionanocomposite thin film has been studied as a sensor element by using surface plasmon resonance (SPR) spectroscopy. The SPR results suggested that potassium ion can be detected by integrating the thin film in the SPR system. This ionophore doped graphene-based bionanocomposite thin film has high potential as novel optical material for metal ion sensing application. [ABSTRACT FROM AUTHOR]

Electrochemical biosensor holds great interest in establishing robust analytical method for Mycobacterium tuberculosis ( M. Tuberculosis ). Herein, fabrication of a highly sensitive electrochemical PNA biosensor based on functionalized graphene oxide (NH 2 -GO) composited with CdS quantum dots (QDs) for the detection of M. Tuberculosis has been described. Firstly, NH 2 -GO/QDs was applied onto screen-printed carbon electrode (SPCE) surface by electro-deposition method, then the PNA probe was immobilized onto the surface of NH 2 -GO/QDs modified SPCE via EDC/NHS coupling technique. Subsequently, the developed PNA biosensor was used to hybridize with target DNA. Differential pulse voltammetry (DPV) was employed to monitor the hybridization event by using methylene blue (MB) as the electrochemical indicator. Under the optimal conditions, a linear detection range of the PNA biosensor was obtained from 1 × 10 −11 to 1 × 10 −7 M with the detection limit of 8.948 × 10 −13 M. The biosensor has successfully discriminated between negative and positive sample of M. Tuberculosis DNA sequences from real sample analysis. [ABSTRACT FROM AUTHOR]

In this study, the preparation of ionophore doped chitosan biopolymer solution using chitosan, glutaraldehyde and p-tert-butylcalix[4]arene-tetrakis(N,N-dimethylacetamide) in acetic acid under mild condition has been described. After the reaction, the ionophore doped chitosan biopolymer thin film was prepared using spin coating technique. The obtained chitosan derivative was confirmed and characterized by Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible near infra-red (UV–Vis–NIR) spectroscopy. Surface morphology, evaluated by atomic force microscopy (AFM), indicates the biopolymer thin film is relatively smooth and homogeneous. Absorption of the thin film is high with optical band gap of 3.177 eV. The incorporation of this derivative thin film with an optical spectroscopy can produce positive responses towards metal ion. This ionophore doped chitosan thin film can be considered as a novel optical material for practical application especially in the field of metal ion sensing. [ABSTRACT FROM AUTHOR]

Abstract: Surface plasmon resonance (SPR) optical sensor, for sensitive and selective detection of Pb2+, was developed in this study based on p-tert-butylcalix[4]arene-tetrakis (BCAT) immobilized in chitosan thin film as an active layer. Pb2+ can be detected by measuring the SPR signal when BCAT immobilized chitosan thin film is exposed to Pb2+ in aqueous solution. The BCAT immobilized chitosan thin film was coated on a gold layer by spin coating technique. The measurements were carried out for Pb2+ concentration ranging from 30ppb to 5ppm. A linear relationship between the shift of SPR angle and concentration of Pb2+ up to 1ppm, with sensitivity of 0.045°ppm−1 has been observed. Pb2+ can also be selectively detected when present in mixtures of heavy metal ions containing Cu2+, Hg2+, Zn2+ and Mn2+ ions. [Copyright &y& Elsevier]

Highlights • Investigation into the development of a multi-disciplinary diagnosis framework for Tuberculosis. • Tuberculosis-specific antibody detection in real time using mobile phone. • Exploration of image processing technique to analyse contents of plasmonic ELISA without experts. • Enhancement of detection accuracy using mobile enabled expert system up to 98.4%. Abstract This paper presents an investigation into the development of an intelligent mobile-enabled expert system to perform an automatic detection of tuberculosis (TB) disease in real-time. One third of the global population are infected with the TB bacterium, and the prevailing diagnosis methods are either resource-intensive or time consuming. Thus, a reliable and easy–to-use diagnosis system has become essential to make the world TB free by 2030, as envisioned by the World Health Organisation. In this work, the challenges in implementing an efficient image processing platform is presented to extract the images from plasmonic ELISAs for TB antigen-specific antibodies and analyse their features. The supervised machine learning techniques are utilised to attain binary classification from eighteen lower-order colour moments. The proposed system is trained off-line, followed by testing and validation using a separate set of images in real-time. Using an ensemble classifier, Random Forest, we demonstrated 98.4% accuracy in TB antigen-specific antibody detection on the mobile platform. Unlike the existing systems, the proposed intelligent system with real time processing capabilities and data portability can provide the prediction without any opto-mechanical attachment, which will undergo a clinical test in the next phase. [ABSTRACT FROM AUTHOR]

Carboxymethyl sago starch-acid hydrogel was prepared via irradiation technique to remove divalent metal ions (Pb, Cu and Cd) from their aqueous solution. The hydrogel was characterized by using Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The removal of these metal ions was analyzed by using inductively coupled plasma-optic emission spectra (ICP-OES) to study the amount of metal uptake by the hydrogel. Parameters of study include effect of pH, amount of sample, contact time, initial concentration of metal solution and reaction temperature. FTIR spectroscopy shows the CMSS hydrogel absorption peaks at 1741 cm −1 , 1605 cm −1 and 1430 cm −1 which indicates the substitution of carboxymethyl group of modified sago starch. The degradation temperature of CMSS hydrogel is higher compared to CMSS due to the crosslinking by electron beam radiation and formed a porous hydrogel. From the data obtained, about 93.5%, 88.4% and 85.5% of Pb, Cu and Cd ions has been respectively removed from their solution under optimum condition. [ABSTRACT FROM AUTHOR]

A novel optical detection system consisting of combination of uricase/HRP–CdS quantum dots (QDs) for the determination of uric acid in urine sample is described. The QDs was used as an indicator to reveal fluorescence property of the system resulting from enzymatic reaction of uricase and HRP (horseradish peroxidase), which is involved in oxidizing uric acid to allaintoin and hydrogen peroxide. The hydrogen peroxide produced was able to quench the QDs fluorescence, which was proportional to uric acid concentration. The system demonstrated sufficient activity of uricase and HRP at a ratio of 5U:5U and pH 7.0. The linearity of the system toward uric acid was in the concentration range of 125–1000 µM with detection limit of 125 µM. [ABSTRACT FROM AUTHOR]

In this study, novel active nanolayers in combination with surface plasmon resonance (SPR) system for zinc ion (Zn 2+ ) detection has been developed. The gold surface used for the SPR system was modified with the novel developed active nanolayers, i.e. chitosan and chitosan–tetrabutyl thiuram disulfide (chitosan–TBTDS). Both chitosan and chitosan–TBTDS active layers were fabricated on the gold surface by spin coating technique. The system was used to monitor SPR signal for Zn 2+ in aqueous media with and without sensitivity enhancement by TBTDS. For both active nanolayers, the shift of resonance angle is directly proportional to the concentration of Zn 2+ in aqueous media. The higher shift of resonance angle was obtained for chitosan–TBTDS active nanolayer due to a specific binding of TBTDS with Zn 2+ . The chitosan–TBTDS active nanolayer enhanced the sensitivity of detection down to 0.1 mg/l and also induced a selective detection towards Zn 2+ . [ABSTRACT FROM AUTHOR]

Precious metal oxides exhibit impressive characteristics that caught worldwide attention due to their promising capacitive performance, excellent electrochemical stability and low resistance, and these metal oxides have been extensively employed in supercapacitor application. This type of supercapacitors is known as redox supercapacitors or pseudocapacitors which applied faradaic process in storing energy in their systems. Thus, new materials with impressive electrochemical performance are highly demanded. In this aspect, cobaltite system with spinel structure has been the subject of intense research due to its established applications in electrochemistry. Besides, carbonaceous materials like activated carbons, carbon nanotubes, graphites, graphenes and fullerenes utilize electric double-layer capacitance whereby energy is stored by charge separation at an electrode/electrolyte interface. With greater development conducted on metal oxides and carbonaceous materials for supercapacitor application, introduction of hybrid and composite electrodes comprise of these two types of materials have been well received. [ABSTRACT FROM AUTHOR]