During literature analysis, it was found that experimental studies dealing with the synthesis of nanoparticles using plant extracts exhibit some problematic aspects resulting in low comparability between the studies and limited reproducibility. A significant portion of these studies lacks sufficient information about the synthesis itself, such as specific concentrations of individual reagents, description of reaction conditions, and others. Another common deficiency in most studies in this field is the absence of information regarding sample preparation for nanoparticle characterization using analytical methods. Moreover, the results of these analyses are, in some cases, insufficiently commented on and discussed. Another issue is the determination of the concentration of the resulting nanoparticle dispersion, which is not addressed at all in some studies (Maťátková et al. 2022).

The primary method for detecting the successful production of metal nanoparticles, alongside visible colour changes in the dispersion within the visible spectrum, is undoubtedly UV-Vis spectrophotometry. With this technique, nanoparticles are characterized by their absorbance peak caused by surface plasmon resonance. Silver nanoparticles produced using Cannabis sativa leaf extract, showed an absorbance peak at a wavelength of 450 nm (Singh et al. 2018b). A study investigating the influence of selected Cannabis sativa cultivars on silver nanoparticle production found that all used extracts produced nanoparticles with an absorption maximum at wavelengths ranging from 432 to 439 nm (Csakvari et al. 2021). In another study exploring the use of Cannabis sativa leaf extract for silver nanoparticle synthesis, the peak absorbance was found to be in the range of 420–450 nm, depending on the ratio of the reaction components (Chouhan and Guleria 2020). In this work, silver nanoparticles synthesized using extracts from Cannabis sativa also exhibited a peak absorbance at 450 nm. Thus, it can be summarized that, according to the literature, silver nanoparticles show absorbance peaks in the range of 420–454 nm, and our findings fall within higher values within this range. A higher wavelength in surface plasmon resonance can signify not only larger nanoparticle diameters but also potentially greater aggregation or changes in the overall nanoparticle morphology. This could suggest that the Cannabis sativa extract used in our synthesis may induce specific structural properties or interactions leading to these larger or aggregated particles.

Gold nanoparticle production using Cannabis sativa extract was investigated in the study by Singh et al. (2018a, b, c), and its success was confirmed, among other methods, by UV-Vis spectrophotometry. The peak absorbance was observed at a wavelength of 550 nm (Singh et al. 2018b). In another study utilizing Cannabis sativa extract, absorbance peaks of nanoparticles formed by mixing different ratios of reaction components were compared. These values ranged from wavelengths of 548 to 551 nm (Hameed et al. 2020). A lower peak absorbance value of 538 nm was measured in a separate study using Cannabis sativa leaf extract (Chang et al. 2021). The spectra of gold nanoparticles produced in this study using plant extracts from Cannabis sativa exhibited absorption maximum at a wavelength of 530 nm. Our findings for gold nanoparticles fell within the lower end of the published range of absorbance peaks (530–551 nm). Lower wavelengths in surface plasmon resonance generally correlate with smaller nanoparticle diameters or more spherical shapes. This could be a result of the specific reductive properties of the Cannabis sativa extract used or the conditions under which synthesis was conducted, underscoring the intricate relationship between the biological reducing agents and nanoparticle characteristics.

Transmission electron microscopy can provide valuable information about the morphology of metal nanoparticles, and when combined with image analysis, it offers an overview of individual nanoparticle sizes and their size distribution in the dispersion. According to available literature, the morphology of silver nanoparticles synthesized using Cannabis sativa extracts mainly showed a spherical shape, with sizes ranging from 20 to 40 nm and 13 to 25 nm. In a study with statistical size analysis, the average size of nanoparticles was identified as 26.5 nm, with a median size of 29.9 nm (Chouhan and Guleria 2020; Singh et al. 2018a, b, c). The conclusions of these studies align with the results of this work, where silver nanoparticles of spherical or ellipsoidal shape were identified during synthesis using Cannabis sativa extract, with diameters ranging from 3 to 21 nm. The smaller size of nanoparticles formed in this study compared to literature suggests that the shift towards higher wavelengths in our UV-Vis spectra may be more indicative of nanoparticle aggregation rather than an increase in individual particle size.

The morphology of gold nanoparticles produced using plant extracts is consistently described in the literature as a mixture of triangular, hexagonal, rod-like, and spherical shapes, which aligns with the morphology of nanoparticles produced in this work. Their sizes ranged from 5 to 40 nm. Gold nanoparticles produced in this study using Cannabis sativa extract exhibited a similar size distribution (2–21 nm) to gold nanoparticles created with Dracocephalum kotschyi leaf extract, which showed diameters ranging from 5 to 21 nm (Barai et al. 2018; Chahardoli et al. 2019; Chang et al. 2021; Singh et al. 2018a, b, c). In accordance with literature, our gold nanoparticles, synthesized using Cannabis sativa extract, displayed mixed morphology with triangular, hexagonal, rod-like, and spherical shapes, and their size distribution (2–21 nm) closely mirrored that of nanoparticles derived from Dracocephalum kotschyi leaf extract.

The specific description of methods for determining the concentration of metal nanoparticles in the produced dispersion is relatively scarce in the literature. Many experimental studies do not address the determination of nanoparticle concentration at all, and for subsequent experiments (e.g., antimicrobial activity tests), the input concentration of the metal precursor is used. This assumes 100% conversion of metal ions without knowledge of the synthesis process mechanism or actual nanoparticle yield (Maťátková et al. 2022). However, some studies do focus on determining the actual nanoparticle concentration in the dispersion.

In a study investigating the production of gold and silver nanoparticles using Cannabis sativa extract, the concentration was determined by inductively coupled plasma mass spectrometry (ICP-MS). This method analyzed individual particles and found nanoparticle counts ranging from 26 to 83 billion particles per milliliter, corresponding to concentrations between 0.7 and 4.5 mg/mL (Singh et al. 2018b). Another study on the synthesis of copper nanoparticles using Magnolia kobus leaf extract revealed a linear relationship between nanoparticle concentration measured by ICP-MS and the absorbance peak size caused by surface plasmon resonance (Lee et al. 2011). In this work, atomic absorption spectrometry was used to determine the concentration of the produced nanoparticles. After separating the nanoparticles from the dispersion using centrifugation, the concentration of metal ions in the resulting supernatant was measured, and the concentration of metal in the nanoparticles was determined by mass balance using the initial molar concentration of the metal precursor. Using this method, the concentration of silver nanoparticles was found to be 334.4 mg/L, and the concentration of gold nanoparticles was found to be 381.9 mg/L.

The elemental composition and internal structure of metal nanoparticles are commonly characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in the literature. In a study investigating the synthesis of silver nanoparticles using Cyperus pangorei extract, XPS confirmed the presence of carbon, nitrogen, oxygen, and silver, identified by peaks at 285.1, 399.0, 531.0, and 366.6 eV, respectively (Parvathiraja et al. 2021). Other studies examining synthesis using extracts from Sophora japonica or Clerodendrum spendens confirmed these results, detecting oxygen (531.6 eV), silver (368.2 and 369.4 eV), and carbon (284.7 eV) (Cheng et al. 2022; Jayakumar and Vedhaiyan 2019). Similar results were obtained in this work. In the dispersion of silver nanoparticles produced using Cannabis sativa extract, carbon (284.9 and 284.6 eV), oxygen (532.9 and 531.4 eV), and silver (368.5 and 367.8 eV) were detected, confirming the presence of both the metal and stabilizing organic molecules. In line with established literature, our findings similarly highlight the presence of key elements like carbon, oxygen, and silver, detected at closely aligned eV values. This consistency not only underscores the efficacy of our nanoparticle synthesis using Cannabis sativa extracts but also attests to the uniform integration of metal with stabilizing organic molecules, mirroring the trends observed in other plant-mediated syntheses.

Information about the internal structure of nanoparticles is further explored using XRD in the literature. Studies describing the synthesis of silver nanoparticles using extracts from Santalum album fruits, Leptadenia reticulata leaves, Aloe vera, or Carya illinoinensis revealed four peaks at 2θ angles of 38.3, 44.6, and 64.8°, corresponding to (1 1 1), (2 0 0), and (2 2 0) planes attributed to the presence of face-centered cubic metallic silver lattice (Javan bakht Dalir et al. 2020; Kumara Swamy et al. 2015; Mehta et al. 2017; Zhang et al. 2013). However, in our study using Cannabis sativa extract, the XRD spectrum revealed additional peaks at 2θ angles of 27.9, 32.3, 46.3, 54.9, and 76.8°, which not only confirm the presence of metallic silver but also suggest the formation of silver chloride, as indicated by the (1 1 1), (2 0 0), (2 2 0), (3 1 1), and (4 2 0) planes, a finding consistent with the study involving Oedera genistifolia (Okaiyeto et al. 2019).

Regarding gold nanoparticles, a study using Phragmites australis leaf extract identified the presence of gold through peaks at 84.1 and 87.8 eV in the XPS spectrum (El-Borady et al. 2021). In other studies, where gold nanoparticles were synthesized using Persicaria salicifolia leaf extract and Selenicereus costaricensis fruit extract, the presence of gold, oxygen, nitrogen, and carbon was confirmed through peaks at 84.1 and 87.8; 531.3 and 532.6; 399.9 and 284.6 and 286.3 eV, respectively, in the XPS spectra (Divakaran et al. 2019; Hosny and Fawzy 2021). Consistent with the literature mentioned above, this work also identified the presence of gold, oxygen, and carbon, with peaks at 84.0; 284.4; and 532.4 eV for Vitis vinifera extract and 84.3; 285.1; and 532.4 eV for Cannabis sativa extract. Aligned with existing literature, our findings confirmed the presence of gold, oxygen, and carbon at closely associated eV values. The almost parallel eV peaks identified in our work, further corroborate the recurring elemental patterns seen in plant-mediated gold nanoparticle syntheses, underscoring the reliability and consistency of green synthesis methods.

XRD analyses in studies using Coleus aromaticus, Phragmites australis, and Jasminum auriculatum extracts for gold nanoparticle production confirmed the presence of face-centered cubic metallic gold lattice. This was achieved by identifying peaks at 2θ angles of 38.3, 44.4, 64.7, and 77.5° corresponding to (1 1 1), (2 0 0), (2 2 0), and (3 1 1) planes (Balasubramanian et al. 2020; El-Borady et al. 2021). The results of this work confirm the findings described in the literature above, with identified peaks at 2θ angles of 38.3, 44.5, 64.8, and 77.7° corresponding to (1 1 1), (2 0 0), (2 2 0), and (3 1 1) planes of metallic gold. Our study aligns seamlessly with established literature, exhibiting nearly identical 2θ angle peaks characteristic of the face-centered cubic metallic gold lattice. The consistency between our detected peaks and those reported in prior research underscores the reproducibility and reliability of the methods employed for gold nanoparticle synthesis across diverse botanical extracts.

Using Fourier-transform infrared spectroscopy (FTIR), functional groups of biomolecules stabilizing the formed nanoparticles were further analysed. Studies examining dispersions of silver or gold nanoparticles synthesized using Cannabis sativa extract detected absorption bands at 3332 cm^-1 indicating the presence of O-H groups, valence vibrations at 1741–1604 cm^-1 indicating C = C bonds, and an increased absorption band at 1019 cm^-1 indicating valence vibration of C-O bonds. Additionally, clear absorption bands of carbonyl group valence vibrations, potentially belonging to proteins, were observed at 1635 cm^-1. Valence vibrations of C-N groups in amines were also observed at 1045 cm^-1. In this work, the presence of O-H groups was confirmed, showing an absorption band at 3305 cm^-1, as well as the presence of C = C bonds indicated by a valence vibration band at 1641 cm^-1. Other identified groups included C-O bonds with absorption bands at 1536 and 1050 cm^-1 and a broader absorption band of aliphatic amines at 1050 cm^-1. For silver nanoparticles and bimetallic nanoparticles synthesized using Cannabis sativa extract in this work, the presence of valence vibration of C-Cl bonds with absorption at 700 cm^-1 was detected. Identical results were achieved in a study examining the synthesis of silver nanoparticles using Cannabis sativa, where these vibrations were attributed to peaks at 769, 687, and 526 cm^-1. The reducing and stabilizing properties were attributed to reducing sugars or proteins, while the purely reducing activity was likely due to terpenoids and flavonoids (Singh et al. 2018a, b, c). Our FTIR analyses, utilized to identify the functional groups of biomolecules stabilizing nanoparticles, agrees with prior research, notably captured the O-H groups, C = C bonds, C-O bonds, and aliphatic amines at comparable wavenumbers. Moreover, the distinctive presence of C-Cl bonds in our synthesized silver nanoparticles mirrors findings in other studies using Cannabis sativa extract, underscoring the consistent role of certain biomolecules such as reducing sugars, proteins, terpenoids, and flavonoids in nanoparticle synthesis and stabilization as outlined in literature mentioned above.

Studies investigating the inhibitory activity of metal nanoparticles synthesized using “green” methods exhibit significant variability, including properties of the produced nanoparticles and tested microorganisms. Similarly, regarding the characterization of biosynthesized nanoparticles, a considerable portion of the studies lacks crucial information, such as the specific microbial strain used, the nanoparticle concentration used for testing, or the exact experimental setup. In terms of experimental design, most studies utilize methods like disk diffusion or well diffusion (Maťátková et al. 2022). Consequently, there is considerable variation in the results presented in these studies, leading to differences in the activity of the specific nanoparticles used.

The inhibitory activity of silver nanoparticles against Pseudomonas aeruginosa has been studied in various research works. In one study using silver nanoparticles synthesized from Rheum palmatum root extract, the minimum inhibitory concentration (MIC) against Pseudomonas aeruginosa ATCC 27,853 was determined as 15 mg/L. Silver nanoparticles produced using Phyllanthus amarus extract exhibited MIC values ranging from 6.25 to 12.5 mg/L against clinical isolates of P. aeruginosa. Another study utilizing silver nanoparticles synthesized with Holarrhena pubescens bark extract found MIC values of 20–25 mg/L. In a study using silver nanoparticles and silver chloride synthesized from Malva sylvestris leaf extract, confirmed by XRD analysis, MIC values for two P. aeruginosa strains were found to be 15.6 and 62.5 mg/L. In this work, silver nanoparticles synthesized from Cannabis sativa extract exhibited MIC values ranging from 0.6 to 2.1 mg/L (Ali et al. 2018; Arokiyaraj et al. 2017; Feizi et al. 2018; Singh et al. 2014). Studies in the literature have consistently reported the inhibitory activity of silver nanoparticles against Pseudomonas aeruginosa, with MIC values ranging from 6.25 mg/l to 62.5 mg/l. Our results using Cannabis sativa extract for nanoparticle synthesis have shown superior antimicrobial efficacy, exhibiting notably lower MIC values ranging from 0.6 to 2.1 mg/l when compared to previously reported ranges.

Bactericidal effects of silver nanoparticles synthesized using “green” methods on adherent P. aeruginosa cells were also investigated in several experimental studies. In one study using industrially produced silver nanoparticles, the minimum bactericidal concentration (MBC) was determined as 4 mg/L. Another study using silver and silver chloride nanoparticles synthesized using Malva sylvestris leaf extract found MBC values ranging from 125 to 250 mg/L. Moreover, in a study utilizing silver nanoparticles synthesized from Hibiscus sabdariffa stem extract, the MBC was not found within the tested concentration range with maximum at 50 mg/L (Aboelmaati et al. 2021; Feizi et al. 2018; Markowska et al. 2014). While previous studies have reported varied bactericidal effects of silver nanoparticles against P. aeruginosa cells, with MBC values ranging from 4 mg/L for industrially produced nanoparticles to undetermined levels up to 50 mg/L for nanoparticles from Hibiscus sabdariffa stem extract, our results show a consistent bactericidal effect within the range of 2.1 to 9.6 mg/L. Notably, the MBC values obtained in our study, utilizing Cannabis sativa extracts, are comparable to those achieved with industrially produced nanoparticles.

Regarding gold nanoparticles produced using “green” methods, there is limited information in the literature about MIC or MBC values. In one study using gold nanoparticles synthesized using sodium tetraborohydrate, MIC was detected in the range of 16–24 g/L. Gold nanoparticles produced from Ziziphus spina-christi leaf extract exhibited inhibitory activity against P. aeruginosa with an MIC of 61 mg/L. Another study using gold nanoparticles synthesized with the use of fucoidan, a polysaccharide originating from brown algae, determined the MIC and MBC as 512 mg/L and 128 mg/L, respectively. The MBIC₅₀ was reported in a study investigating the activity of gold nanoparticles synthesized using Tinospora cordifolia stem extract, with an MBIC₅₀ value of 150 mg/L (Ali et al. 2020; Alzahrani et al. 2022; Khan et al. 2019; Zhao et al. 2010). In this work, gold nanoparticles exhibited lower efficacy compared to silver nanoparticles, with MIC₅₀ values ranging from 59.6 to 159.7 mg/L and some strains (e.g., P. aeruginosa ATCC 15442) showing no MIC₅₀ in the concentration range studied. MBIC₅₀ was not found in most studied strains (e.g., P. aeruginosa DBM 3081 or ATCC 10145), and when found, it ranged from 7 to 98.4 mg/L. The variability in MIC and MBIC50 values for gold nanoparticles, as observed across various studies, underscores the significant impact of synthesis methods and materials on their antimicrobial effectiveness. Particularly, our findings of lower efficacy in certain P. aeruginosa strains highlight the complex interplay between the biological source of the synthesis material and the nanoparticles’ antimicrobial properties.

This study demonstrates the successful synthesis of silver and gold nanoparticles using agricultural waste extract from Cannabis sativa. These nanoparticles exhibited remarkable antimicrobial activity against P. aeruginosa, a common pathogen responsible for nosocomial infections and a major contributor to antibiotic resistance. The utilization of agricultural waste for nanoparticle production presents a sustainable and cost-effective approach. Developing nanoparticle coatings derived from such waste sources holds great potential for combating nosocomial infections, addressing antibiotic resistance, and offering affordable solutions for infection control in healthcare settings.

Future research should focus on optimizing the synthesis process to improve the antimicrobial properties and stability of these nanoparticles. Additionally, it is crucial to evaluate their efficacy in real-world applications, such as medical devices and wound dressings, to enable practical implementations. Leveraging the potential of nanoparticles derived from Cannabis sativa waste opens avenues for sustainable and accessible solutions in infection control and healthcare management.