Nanomaterials
Stirring time sets GSH-capped silver nanoparticle size
Open access · cc by · source: Europe PMC
Glutathione reduces AgNO3 at 60 °C; longer stirring grows spherical Ag nanoparticles from about 3 to 6 nm.
Study at a glance
- Design
- Other — Time-dependent glutathione-capped AgNP growth tracked by SPR/TEM/XRD
- N
- Nanomaterial synthesis kinetics — no sample N
- Population
- Silver nanoparticles prepared with glutathione at 60 °C
- Outcome
- Stirring-time dependence of particle diameter and SPR
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
SPR at 344–354 nm appears after long stirring; fcc Ag forms; TEM diameters are 3.20, 4.83 and 6.19 nm at 36, 48 and 72 h. FT-IR shows GSH S–H/N–H bands vanish on binding.
Methodology
Authors stirred AgNO3 with glutathione at 60 °C for 1–72 h and tracked SPR, XRD, TEM/SEM-EDX, FT-IR and zeta potential.
Limitations
No kinetic rate law or nucleation model; biological tests are only proposed; size dispersity still grows with time.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Powder XRD of silver colloids is a phase fingerprint, not a molecular structure. Blackberry-leaf Ag nanoparticles show peaks at 38.1°, 44.4°, 54.5° and 77.9° with TEM diameters 50–120 nm and SPR at 449 nm. Glutathione-capped Ag stirred at 60 °C is fcc; TEM diameters grow 3.20 → 4.83 → 6.19 nm at 36, 48 and 72 h while SPR sits at 344–354 nm.
Evidence for the claim as stated.
Stirring time is another TEM-readable size knob. Glutathione-capped Ag at 60 °C grows TEM diameters 3.20, 4.83 and 6.19 nm at 36, 48 and 72 h as fcc metal forms and SPR appears at 344–354 nm. Blackberry-leaf Ag is much larger by TEM (50–120 nm) with SPR at 449 nm — same metal, different length scale, both still images of dried particles.
Evidence for the claim as stated.
Silver SPR is a size/composition reporter, not a structure determination. GSH-capped Ag develops SPR at 344–354 nm as TEM diameters go 3.20 → 4.83 → 6.19 nm (36/48/72 h). Aqueous glycerol (10–100%) keeps SPR in 410–450 nm and particles <10 nm up to ~60% glycerol, then SPR and size rise above ~70–80% glycerol (about 10–160 nm). Gamma-made Ag/Se/Ag–Se particles are tracked at 406, 518 and 420 nm with mean sizes 10.95, 20.54 and 12.69 nm.
Evidence for the claim as stated.
Absorption near 400 nm is not one phenomenon. GSH and glycerol silver papers read it as a plasmon that tracks particle size; the titanyl paper reads a Ti–peroxo charge-transfer colour for an H₂O₂ LOD; ProCharTS reads a weak protein CT tail (ε hundreds M⁻¹ cm⁻¹) out to 800 nm; the Fe paper needs 370–1200 nm transient spectra to assign PALCT versus ⁵MC. A student who says 'the UV-vis peak proved it' has not chosen among those assignments.
Evidence for the claim as stated.
GSH-capped Ag uses SEM-EDX beside TEM diameters of 3.20, 4.83 and 6.19 nm (36/48/72 h) and SPR at 344–354 nm; gamma Ag/Se/Ag–Se particles average 10.95, 20.54 and 12.69 nm. Those papers are particle-sizing problems. A different indexed study maps ITO with a 50 nm SECCM pipette: the entire surface is active, only 0.2% of area is reversible (k⁰ ≥ 1 cm s⁻¹), 85.2% has mean k⁰ = 4.2×10⁻² cm s⁻¹, and a weighted average k⁰ ≈ 3.61×10⁻² cm s⁻¹ — activity, not an SEM micrograph.
Evidence for the claim as stated.
TEM versus SEM is a length-scale choice, not a preference. Ultra-small glycerol Ag (<10 nm) is a TEM problem; SEM is reserved for the larger 10–160 nm branch. GSH Ag TEM diameters of a few nanometres are below what most SEM images of a catalyst or hydrogel are used to claim. Mixing those papers into one 'electron microscopy size' is the error.
Evidence for the claim as stated.
Disappearance of ligand IR bands can report binding without giving a size. GSH-capped Ag stirred at 60 °C loses S–H/N–H intensity on the nanoparticle; fcc Ag forms; TEM diameters are 3.20, 4.83 and 6.19 nm at 36, 48 and 72 h with SPR at 344–354 nm. No kinetic rate law is fitted.
Evidence for the claim as stated.
FTIR can confirm a bond and still not be the performance metric. Vanishing GSH S–H bands do not give a nucleation rate; hydrogel FTIR does not give 90.64% DEE; titanyl FTIR of a peroxo does not give 0.04 ppb — that LOD is from absorbance noise and sensitivity. Characterisation versus assay is the split.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Absorption near 400 nm is not one phenomenon. GSH and glycerol silver papers read it as a plasmon that tracks particle size; the titanyl paper reads a Ti–peroxo charge-transfer colour for an H₂O₂ LOD; ProCharTS reads a weak protein CT tail (ε hundreds M⁻¹ cm⁻¹) out to 800 nm; the Fe paper needs 370–1200 nm transient spectra to assign PALCT versus ⁵MC. A student who says 'the UV-vis peak proved it' has not chosen among those assignments.
- Supports · Paper titanyl sensor sees H2O2 vapor at 0.04 ppb
- Supports · Charged amino acids absorb past 250 nm
- Supports · Wide-band TA maps an Fe(II) four-state cascade
TEM versus SEM is a length-scale choice, not a preference. Ultra-small glycerol Ag (<10 nm) is a TEM problem; SEM is reserved for the larger 10–160 nm branch. GSH Ag TEM diameters of a few nanometres are below what most SEM images of a catalyst or hydrogel are used to claim. Mixing those papers into one 'electron microscopy size' is the error.
- Supports · Glycerol tunes silver nanoparticle size
FTIR can confirm a bond and still not be the performance metric. Vanishing GSH S–H bands do not give a nucleation rate; hydrogel FTIR does not give 90.64% DEE; titanyl FTIR of a peroxo does not give 0.04 ppb — that LOD is from absorbance noise and sensitivity. Characterisation versus assay is the split.
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