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Research on hydrogels as soil conditioners has been developed based on hydrogels copolymerized with composite materials in the form of chitosan and TiO 2 to overcome low physical properties and low swelling of polyacrylamide. The aims of the study are synthesis, characterization, application of hydrogels, and determination of the physical and chemical properties of soil and the growth of soybean plants. Synthesis of chitosan-co-polyacrylamide-TiO 2 crosslinked glutaraldehyde hydrogel was prepared by the chemical crosslinking method. The characterization of hydrogel was performed by using Fourier Transform Infra-Red (FTIR) and Scanning Electron Microscope (SEM). FTIR spectrum shows the functional groups of chitosan co-polyacrylamide-TiO 2 crosslinked glutaraldehyde which includes OH functional groups (3408.22 cm-1), NH (1602.85 cm-1), C=O (1502 cm-1), CN (1600.92 cm-1), and Ti-O (619.15 cm-1). The SEM image shows the formation of pores and cavities in the hydrogel. The application of hydrogels in soybean plants shows differences in physical and chemical properties of soil and plant growth. The use of all variations of hydrogel had no signifi cant effect on soil physical properties including temperature, humidity, and bulk density. Meanwhile, hydrogels with TiO 2 concentration of 60 ppm infl uence signifi cantly to the chemical properties of soil such as organic carbon, cation exchange capacity (CEC), and level of nitrogen, phosphorus, and potassium in the soil. The optimum number of leaves, plant height, total dry weight are 68 leave blades, 207 cm, and 20.6 g, respectively. This optimum condition was found in the use of KTiKPAG60 hydrogel. The results showed that chitosan-co-polyacrylamide-TiO 2 crosslinked glutaraldehyde has the potential to be a soil conditioner.

Novel, sensitive, selective, efficient and portable electrochemical biosensors are needed to detect residual contaminants of the pesticide 1-naphthyl methylcarbamate (carbaryl) in the environment, food, and essential biological fluids. In this work, a study of nanocomposite-based Ag reduced graphene oxide (rGO) and chitosan (CS) that optimise surface conditions for immobilisation of acetylcholinesterase (AChE) enzyme to improve the performance of catalytic biosensors is examined. The Ag/rGO/CS nanocomposite membrane was used to determine carbaryl pesticide using a potentiometer transducer. The AChE enzyme-based biosensor exhibits a good affinity for acetylthiocholine chloride (ATCl). It can catalyse the hydrolysis of ATCl with a potential value of 197.06 mV, which is then oxidised to produce a detectable and rapid response. Under optimal conditions, the biosensor detected carbaryl pesticide at concentrations in the linear range of 1.0 × 10−8 to 1.0 μg mL−1 with a limit of detection (LoD) of 1.0 × 10−9 μg mL−1. The developed biosensor exhibits a wide working concentration range, detection at low concentrations, high sensitivity, acceptable stability, reproducibility and simple fabrication, thus providing a promising tool for pesticide residue analysis.

<p>Sintesis kitosan telah dikembangkan dengan metode pemanasan <em>microwave </em>(MW) menggunakan pelarut alkali untuk kebutuhan berbagai aplikasi yang salah satunya sebagai membran immobilisasi enzim. Penelitian membran kitosan dengan immobilisasi enzim asetilkolinesterase (AChE) sebagai elektrode biosensor terus berkembang untuk menghasilkan perangkat mutakhir yang dapat mendeteksi pestisida. Penelitian ini bertujuan untuk menghasilkan biosensor berbasis elektrode membran Au/Kitosan/GTA/AChE untuk deteksi pestisida karbaril yang memiliki batas deteksi yang rendah, sensitivitas yang tinggi, waktu respon cepat dan presisi yang baik. Kitosan dihasilkan dari isolasi kitin dari kulit udang menggunakan alat MW dan pelarut NaOH dengan daya 450 Watt selama 15 menit menghasilkan rendemen sebesar 31,50%. Karakterisasi FTIR kitosan diidentifikasi adanya gugus O–H, C–N, N–H amina, dan C=O dengan intensitas yang rendah serta derajat deasetilasi rata-rata 95,6 ± 0,1%. Komposisi elektrode membran Au/Kitosan/GTA/AChE menggunakan kitosan dengan variasi konsentrasi 2, 5, dan 8% (b/v) dan glutaraldehid (GTA) 25%, kawat Au dan diimobilisasikan enzim asetilkolinesterase (AChE). Elektrode membran Au/Kitosan 2%/GTA/AChE memiliki karakteristik yang baik dimana nilai sensitivitas sebesar 23,318 mV.dekade^-1 pada rentang konsentrasi pestisida 10^-7– 10^-1 µg mL^-1 dengan batas deteksi (LoD) 1 × 10^-7µg mL^-1. Waktu respon yang diperoleh yaitu pada rentang waktu 5– 7 menit dengan <em>relative standard deviation</em> (RSD) sebesar 0,588%. Biosensor yang dikembangkan menunjukkan sensitivitas, stabilitas dan reproduktifitas yang baik, sehingga elektrode membran Au/Kitosan/GTA/AChE menjanjikan untuk alat deteksi pestisida. </p><p><strong>Synthesis of Chitosan from Shrimp Shell as Electrode Membrane Material Au/Chitosan/GTA/AChE for Pesticide Detection. </strong>Chitosan synthesis has been developed using the heating by microwave (MW) method using alkaline solvents for various applications, one of which is an enzyme immobilization membrane. Chitosan membrane research with immobilization of the enzyme Acetylcholinesterase (AChE) as a biosensor electrode developed to produce advanced devices that can detect pesticides. This study aims to produce a biosensor based on Au/Chitosan/GTA/AChE membrane electrodes to detect carbaryl pesticides with a low detection limit, high sensitivity, fast response time, and good precision. Chitosan was produced from the isolation of chitin from shrimp shells using an MW device and NaOH solvent with a power of 450 Watts for 15 minutes to produce a yield of 31.50%. The FTIR characterization of chitosan identified the presence of O–H, C–H, C–N, N–H amine groups and C=O with low intensity and the average degree of deacetylation of 95.6 ± 0.1%. The composition of Au/Chitosan/GTA/AChE membrane electrodes used chitosan with various concentrations of 2, 5, and 8% (w/v) and glutaraldehyde (GTA) 25% on Au wire and immobilized with AChE enzyme. The Au/Chitosan 2%/GTA/AChE membrane electrode has good characteristics where the sensitivity value is 23.318 mV.decade^-1 in the pesticide concentration range of  10^-7– 10^-1 µg mL^-1 with a detection limit (LoD) of 1 × 10^-7 µg mL^-1. The response time obtained is in the range of 5 ‒ 7 minutes with a relative standard deviation (RSD) of 0.588%. The developed biosensor shows good sensitivity, stability, and reproducibility, thus Au/Chitosan/GTA/AChE membrane electrodes are promising for pesticide detection.</p>

TiO 2 photocatalytic process has been developed and used in various applications. One of the use of TiO 2 is related to the hydrophilic properties, which is shown with a small contact angle between the surface of object and liquid (<10°). In this study, TiO 2 was coated on a glass surface with the dip coating method. TiO 2 catalyst was prepared by titanium tetraisopropoxide (TTIP) as precursor and polyethylene glycol (PEG) as template calcined at a temperature of 450°C. The addition of PEG was varied to obtain optimal conditions. Measurement of Diffuse Reflectance Spectroscopy UV-Vis (DRS UV-Vis) showed a decrease in the value of the band gap for TiO 2 , TiO 2 -PEG 200, TiO 2 -PEG 400 and TiO 2 -PEG 1000 were 3.153 eV; 3.056 eV; 3.012 eV and 2.975 eV, respectively. Results of contact angle measurements have been achieved hydrophilic properties. While, the photocurrent response of the three TiO 2 working electrodes added the PEG 200, PEG 400, PEG 1000 were 2.3×10 -3 A, 2.2×10 -3 A and 4.2×10 -3 A, respectively. Therefore, PEG could improve the performance of TiO 2 catalysts.