http://theeditorsblog.net/2011/05/07/single-quotation-marks-a-readers-question/
A few stories I’ve read use a strange style of quotation marks: Double quotation marks for quotations, and single quotation marks for single words.
For example:
She said wearily, “Hello, how are you?” but most of them didn’t even hear her feeble ‘greeting’ attempt.
No.
As the article in the link explains, you should use single quotation marks only if you normally start quotations with single quotation marks.
So, it’s either:
She said wearily, 'Hello, how are you?’ but most of them didn’t even hear her feeble 'greeting’ attempt.
Or:
She said wearily, “Hello, how are you?” but most didn’t even hear her feeble “greeting” attempt.
There are also a few technical cases where single quotation marks are used, such as plant cultivars. In these cases, you should use single quotation marks even if you normally start quotations with double quotation marks:
The specimen was a Malus domestica 'Red Delicious’. “So, an apple,” he said.