= Solution
In a <polyol process>, a hot polyol such as <ethylene glycol> acts as <solvent> and reductant for a <silver> precursor. <Nucleation> creates seeds; controlled <reduction> supplies atoms for their subsequent growth, while <polyvinylpyrrolidone> <adsorption> and seed <crystal twinning> favour anisotropic growth. For the common <silver nanowire> route, a fivefold-twinned seed can develop into a pentagonal wire with predominantly $\{100\}$ side faces and growth at less-passivated ends. Cross-sectional microscopy and <diffraction> of microtomed wires provide evidence for that twinned structure rather than an inference from a long outline alone.<Polyol Synthesis of Uniform Silver Nanowires: A Plausible Growth Mechanism and the Supporting Evidence by Yugang Sun and others>[Nano Letters 3 (2003), pp. 955–960, pentagonal cross sections and fivefold twinning]{ref}
The <aspect ratio> depends on seed population and twin survival, relative end/side growth rates, precursor feed and <reduction> rate, <PVP> coverage, <temperature>, trace halides, dissolved oxygen and growth time. High <aspect ratio> requires a suitable population of twinned seeds, suppression of competing particle <nucleation> and continued atom supply while sidewall thickening is restrained. These variables must be controlled together; adding more capping <polymer> alone is not a universal recipe. Advantages are solution processing, substantial yield and tunable dimensions without an etched hard template. Disadvantages include sensitive batch reproducibility, particle by-products, residual insulating <ligand>, purification, oxidation/tarnish and <nanowire junction resistance> in later films. Compare seed/capping/halide controls using microscopy and size distributions, not only solution colour.
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