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Delicate nano-flowers coaxed from simple seeds
Aperture
24 | NewScientist | 22 00 June Month 2013 2013
In the nano-garden ADD nutrients, consider the temperature, monitor precipitation – the basics of gardening are much the same even at the nanoscale. Cultivators of the very small have grown flowers, exotic fruits and whole meadows from molecules assembled out of solution. But unless they use expensive, laborious techniques, all they can do is plant the seeds and watch as crops spring up uncontrolled. Wim Noorduin of Harvard University and his colleagues wanted a less costly way to tend their nano-flowers and create intricate arrangements (Science, doi.org/mtt). They made the bouquet in the false-colour image on the left in three stages. First, they chilled a solution of sodium silicate and barium chloride to 4 °C. At this temperature, more carbon dioxide from the air dissolves in the liquid, triggering a chemical reaction that lays down bundles of barium carbonate and silica (red). Then they moved the miniature basket to a room-temperature strontium chloride solution. As CO2 dissolved in this liquid, strontium carbonate stems (green) began to emerge. Opening and closing a lid on the beaker generated pulses of CO2 that changed the growth rate and made the stems spread into iris-like blossoms, each just 25 micrometres across. Similar finetuning made the barium-based roses below. Tiny ikebana is not just an end in itself. Crafting nano-shapes can improve optics and electronics, say Noorduin and his team. Victoria Jaggard n
Photographer Wim Noorduin Harvard University
0022 Month June 2013 | NewScientist | 25
24 | NewScientist | 22 00 June Month 2013 2013
In the nano-garden ADD nutrients, consider the temperature, monitor precipitation – the basics of gardening are much the same even at the nanoscale. Cultivators of the very small have grown flowers, exotic fruits and whole meadows from molecules assembled out of solution. But unless they use expensive, laborious techniques, all they can do is plant the seeds and watch as crops spring up uncontrolled. Wim Noorduin of Harvard University and his colleagues wanted a less costly way to tend their nano-flowers and create intricate arrangements (Science, doi.org/mtt). They made the bouquet in the false-colour image on the left in three stages. First, they chilled a solution of sodium silicate and barium chloride to 4 °C. At this temperature, more carbon dioxide from the air dissolves in the liquid, triggering a chemical reaction that lays down bundles of barium carbonate and silica (red). Then they moved the miniature basket to a room-temperature strontium chloride solution. As CO2 dissolved in this liquid, strontium carbonate stems (green) began to emerge. Opening and closing a lid on the beaker generated pulses of CO2 that changed the growth rate and made the stems spread into iris-like blossoms, each just 25 micrometres across. Similar finetuning made the barium-based roses below. Tiny ikebana is not just an end in itself. Crafting nano-shapes can improve optics and electronics, say Noorduin and his team. Victoria Jaggard n
Photographer Wim Noorduin Harvard University
0022 Month June 2013 | NewScientist | 25