The synthesis of silver nanoparticles via plant-mediated approach is an emerging area of research interest worldwide. The procedure is cost-effective and does not require the use of toxic chemicals and complicated reaction conditions. In the present investigation, silver nanoparticles were prepared using the leaf extracts of Ixora coccinea Linn., a common ornamental shrub in the Philippines, as the reducing agent. The effect of pH on the synthesis was investigated, and results showed that the quality of the synthesized silver nanoparticles changes in varying pH of the reducing agent.

In response to the remote learning and teaching setup in science due to the COVID-19 pandemic, a lab at-home experiment was conducted where various plant materials were prepared and used as natural acid-base indicators for various household substances. The experiment is designed for the students to apply the fundamentals of intensive laboratory for science education: laboratory safety, laboratory apparatus, laboratory techniques, data documentation, and lab report writing. Presented herein are the results obtained during the experiments conducted at home that focused on the application of various plant extracts as natural indicator. Observable color changes showed that the tested plant extracts responded to the acidity and alkalinity of the various household substances. The science behind the color changes is attributed to the presence of various phytochemicals that change colors when protonated and deprotonated. The potential of the results obtained in the experiments is very promising as it can be further developed and optimized to an analytical procedure that can be applied in testing of acidity and alkalinity in various applications such as food safety and quality, environmental monitoring, materials testing, pharmaceutical analysis, and clinical diagnostics. Moreover, the experiment explored here presented lab teaching strategies that can be applied in the remote learning setup: formulate and design a home-based laboratory experiment that will cover the underlying scientific theories and skills and provide the students the opportunity to explore, improvise, apply, and present information that will holistically develop them as science educators for their current and prospective students.

The application of noble metal nanoparticles such as silver (AgNPs) in sensing small molecules has attracted many researchers worldwide. In this present investigation, AgNPs were synthesized via a one-pot and green strategy of using alkaline sucrose solution as the reducing agent. The AgNPs were characterized by UV-Vis spectroscopy and dynamic light scattering techniques. The AgNPs were confirmed through its surface plasmon band and had a narrow size distribution and good colloidal stability. The AgNPs were then applied as sensor probes in the visual detection of hydrogen peroxide. The sensing mechanism is based on the reduction-oxidation reactions that led to the observed color changes. The detection limit was found to be 1 x 10 -3 M as monitored through visual observation and image analysis. The study showed a great promise on the potential of AgNPs in the detection of small molecule targets for environmental and health sensor applications.

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The present study focuses on the exploration of a synthetic procedure for the preparation of green silver nanoparticles. Using lactose as the reducing agent, the reaction mixture containing the silver precursor was exposed to ultrasonic irradiation at ambient temperature and conditions. To optimize the synthesis, the pH levels and concentration of lactose were varied. Using lactose at acidic level, no silver nanoparticles were produced since there was no color change observed after the sonication. On the other hand, silver nanoparticles were produced using alkaline lactose solutions as evidenced by the formation of yellow-colored products. Infrared spectrometry revealed the functional groups responsible for the reduction and capping of the nanoparticles. The sonochemical route provided a synthetic strategy for the production of quality nanoparticles with potential chemical and biological activities.

Pests are one of the constraints in agricultural crops, such as the army worm (Spodoptera exigua), that is considered as one of the most harmful pests in the vegetative phase. In this work, ethanolic leaf extracts of common plants Senna sophera (L.) Roxb., Syzygium cumuni, and Annona squamosa Linn. in Llanera, Nueva Ecija, Philippines were prepared and the phytochemical constituents were detected. Direct spraying of the extracts was done to test the effectiveness of the biopesticides. Results showed that the extracts have varying effectivity as biopesticide against Spodoptera exigua and can be related to the chemical constituents present in the extracts. Considering the results from this investigation, the easy availability and effectiveness of these natural pesticides can be developed as alternatives to conventional synthetic pesticides.