| Metadata | Details |
|---|
| Publication Date | 2024-05-02 |
| Journal | Brazilian Journal of Development |
| Authors | Edippuli Arachchige Dona Hiruni Amasha, Mathivathani Kandiah |
| Institutions | University of Colombo |
| Analysis | Full AI Review Included |
- Green Synthesis Protocol: Silver Nanoparticles (AgNPs) were successfully synthesized using aqueous leaf extracts from five varieties of Cordyline fruticosa, utilizing a cost-effective and non-toxic water-based reduction method.
- Structural Characterization: SEM analysis confirmed the formation of spherical AgNPs with a narrow diameter range of approximately 40-50 nm.
- Electronic Properties: Bandgap energy calculations (ranging from 2.668 eV to 2.934 eV) classify the synthesized AgNPs as semiconductors, suitable for photo-activated applications.
- Enhanced Antioxidant Activity: AgNPs exhibited significantly higher Total Flavonoid Content (TFC), Total Phenolic Content (TPC), and DPPH radical scavenging activity (up to 94.7%) compared to the raw aqueous extracts.
- Selective Antimicrobial Efficacy: The synthesized AgNPs demonstrated better bactericidal activity against the Gram-positive bacterium Staphylococcus aureus than against the Gram-negative Escherichia coli.
- Catalytic Dye Degradation: AgNPs showed potent photocatalytic activity, achieving significant degradation of Malachite Green (MG) dye within 5 minutes when coupled with the reducing catalyst NaBH4.
| Parameter | Value | Unit | Context |
|---|
| Nanoparticle Morphology | Spherical | - | SEM analysis |
| Nanoparticle Diameter | 40-50 | nm | 4PC AgNPs |
| Optimal Synthesis Temperature (1CC, 4PC) | 90 | °C | Incubation time: 45 minutes |
| Optimal Synthesis Temperature (2WR) | 60 | °C | Incubation time: 45 minutes |
| Surface Plasmon Resonance (SPR) Peak | 400 | nm | UV/Vis characterization |
| Bandgap Energy (Eg) Range | 2.668 to 2.934 | eV | Semiconductor classification |
| Photocatalytic Rate Constant (k) | 1.398 | min-1 | 4000 ppm AgNPs + NaBH4 |
| Photocatalytic Degradation Time | 5 | minutes | Malachite Green dye (with NaBH4) |
| Highest DPPH Scavenging Activity | 94.72 | % | 1CC AgNP solution |
| Highest TFC (4PC AgNP) | ~8,000,000 | ”g QE/100g | Total Flavonoid Content |
| Bacterial Strain Sensitivity | Gram-positive > Gram-negative | - | Higher ZOI observed for S. aureus |
- Leaf Extract Preparation:
- Raw leaves were shade-dried, powdered, and mixed with distilled water (2g powder in 50 mL water).
- Extraction was performed at 98°C for 10 minutes, followed by filtration.
- Silver Nanoparticle Synthesis:
- 1 mL of leaf extract was mixed with 9 mL of 1 mM AgNO3 solution.
- Optimization was conducted across temperatures (60°C, 90°C, Room Temperature) and time periods (15, 30, 45, 60 minutes, 24 hours).
- Morphological and Electronic Characterization:
- SEM: 4PC AgNPs were centrifuged, oven-dried at 40°C, gold-coated, and analyzed using a Hitachi SU6600 SEM to determine size and shape.
- UV/Vis: Absorbance was measured (320-520 nm) to confirm SPR peak (400 nm) and calculate bandgap energy (E = hc/λ).
- Antioxidant Assays:
- Total Flavonoid Content (TFC) was measured using the AlCl3 method (Absorbance at 415 nm).
- Total Phenolic Content (TPC) was measured using the Folin-Ciocalteau assay (Absorbance at 760 nm).
- DPPH assay was used to quantify free radical scavenging activity (Absorbance at 517 nm).
- Antimicrobial Testing:
- The well-diffusion technique was used against E. coli and S. aureus.
- Results were compared against a positive control (Gentamycin discs).
- Photocatalytic Activity Assessment:
- Malachite Green (MG) dye solution (1 mM) was treated with AgNPs (267 ppm or 4000 ppm).
- The reaction was catalyzed by the addition of 0.2 M NaBH4 solution.
- The mixture was exposed to sunlight, and degradation was monitored via absorbance measurements (320-800 nm) over 15 minutes.
- Wastewater Treatment: Utilization of AgNPs as photocatalysts for the rapid, eco-friendly degradation of persistent azo dyes (like Malachite Green) in industrial effluent, offering a non-toxic alternative to conventional chemical treatments.
- Antimicrobial Coatings and Textiles: Incorporation of AgNPs into fabrics or surface coatings to manufacture antimicrobial textiles and wound dressings, leveraging their strong bactericidal effect, particularly against Gram-positive pathogens such as S. aureus.
- Pharmaceutical and Nutraceutical Development: Use of the synthesized AgNPs, rich in phytochemicals (phenols and flavonoids), as potent antioxidants for the development of treatments targeting free-radical mediated diseases and oxidative stress.
- Semiconductor and Optoelectronic Devices: Application of the low bandgap (2.6-2.9 eV) AgNPs in devices requiring photo-responsive semiconductor materials, potentially in visible-light activated systems.
- Biosensing Technology: Exploitation of the strong Surface Plasmon Resonance (SPR) of the 40-50 nm spherical AgNPs for developing highly sensitive biosensors and imaging agents.
View Original Abstract
The biological synthesis of nanoparticles using plants or microorganisms has gained attention in the recent past, mainly due to its eco-friendly nature and because they can be used in a vast variety of fields such as medicine, agriculture and textiles. The current study focuses on the green synthesis of silver nanoparticles (AgNPs) using five varieties of Cordyline fruticosa (candy cane, waihee rainbow, exotica, pink cascade and pink diamond) leaves, and assessing their antioxidant, photocatalytic and antimicrobial activities. SEM analysis of pink cascade-AgNPs shows they are spherical and in the range of 40-50nm. Band gap energy calculations reveal that synthesized AgNPs can act as semiconductors. Total flavonoid content, total phenolic content and total antioxidant capacity were analyzed and the DPPH-free radical scavenging assay was performed. These showed that AgNPs had higher antioxidant activity compared to aqueous extracts. The antibacterial activity of AgNPs and aqueous extracts was assessed using cultures of Escherichia coli and Staphylococcus aureus. Extracts and AgNPs showed better bactericidal effect on S.aureus. Photocatalytic activity of synthesized AgNPs was assessed using malachite green as a model dye and significant degradation of the dye was observed when AgNPs were added together with catalyst NaBH4. According to the results obtained from this study, it can be seen that AgNPs synthesized using Cordyline fruticosa have potential in different aspects including treatment of free-radical mediated diseases, overcoming antibiotic resistance, treatment of bacterial diseases and overcoming environmental pollution.