Scientists have created a scent(气味)-delivery system that releases a pleasant fragrance when you sweat. Apply it to your skin, and the more you sweat, the better you’ll smell. That’s because the perfume only gets released upon contact with moisture(湿气).
Chemists from Harvard University combined two compounds(化合物) to create their new system. One chemical is alcohol-based. This is the nice-smelling perfume. The other chemical is an ionic liquid(离子性液体), which is a type of salt that is liquid at room temperature. Ionic liquids are made of ions---molecules that have lost or gained one or more electrons. If the molecule loses electrons, it will have a positive charge. If it gains electrons, it gets a negative charge. Ionic liquids contain the same number of positive and negative ions, which makes them neutral(中性的), with no overall electric charge. In general, ionic liquids have no smell.
When the perfume and ionic liquid are mixed together, a chemical reaction occurs. This bonds the molecules to each other. The reaction also temporarily inactivates(使不活跃) the perfume’s molecules. So when applied to the skin, the new perfume has no scent in the beginning. But adding water or sweat breaks the bond between the molecules. That releases the scent into the air.
“The rate of the release of the fragrance depends on how much you sweat, in other words, how much water is available,” explains chemist Nimal Gunaratne from Harvard University, who led the research. “Sweat is like the command to let the fragrance go.”
Christian Quellet is a chemist who has worked in the perfume industry for a long time. He is now an independent consultant based in Switzerland. “Gunaratne’s perfume opens the door to new developments and applications of fragrance controlled-release systems,” he says. Controlled-release systems allow small quantities of some compounds that they hold to enter the environment slowly.
The system also traps some chemicals in sweat that are responsible for the bad sweat smell. These compounds are called thiols (硫醇). Just as water does, thiols break apart the bond that ties the perfume to the ionic liquid. When this happens, the thiols attach to the ionic liquid and their bad scent is inactivated as the perfume had been. This means the water in sweat and its thiols are both able to release the fragrance from the newly developed perfume.
【小题1】Which of the following makes the scent delivery system special?| A．When it releases scent can be well controlled. |
| B．No perfume is required in the system. |
| C．The scent can last for a long time. |
| D．Sweat can help release the scent. |
| A．the perfume comes into contact with the skin |
| B．the perfume and ionic liquid contact each other |
| C．the perfume’s molecules are inactivated by water |
| D．sweat activates the molecules of the perfume in the mixture |
| A．the more you sweat, the better you will smell |
| B．the perfume can’t always cover the bad smell. |
| C．how much water is available doesn’t matter much |
| D．how you smell depends on how much perfume you use |
| A．Indifferent. | B．Favorable. | C．Doubtful. | D．Critical. |
