These FTSE-listed giants are grabbing the headlines! Should you buy?

Nanotechnology specialist Nanoco(LSE: NANO) was recently dealing 6% higher from Friday's close after unveiling a deal with pharmaceuticals and science colossus Merck.

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The accord will see Merck market Nanoco's cadmium-free quantum dot technology, it was announced, with a view to the US giant eventually building its own production facility to meet rising demand for display units using this hardware. Nanoco will receive a licence fee and royalties on Merck's sales.

Nanoco's share price has exploded since the Brexit referendum, the manufacturer's relationship with an array of multinational clients proving the perfect tonic for concerned investors. The stock has risen 85% since the vote, with Monday's push taking it to levels not seen since last July.

While Nanoco is expected to remain lossmaking until the close of next year, I believe the Mancunian star's expertise in a fast-growing tech segment should underpin explosive earnings growth in the coming years.

Developing markets drag

Engineer Keller Group (LSE: KLR) hasn't fared so well in Monday trade, however, the stock last changing hands 11% lower following a disappointing half-year update

Keller announced that revenues hit a record £849.7m between January and June, up 12% year-on-year. But operating profit slipped 6% during the period, to £35.6m, thanks to big losses in its Asia Pacific region.

While in North America and Europe Keller has outperformed, it has said that it expects full-year results to be at the lower end of previous guidance thanks to challenging market conditions across markets such as Australia, Singapore and Malaysia.

Today's share price move leaves Keller dealing on a forward P/E rating of 9.4 times, a situation that could see plenty of bargain hunters piling in. But investors should be aware of further share price weakness should emerging market coolness intensify, and patchy economic data in Europe and the US indicates upcoming weakness for its two biggest divisions.

Hitting turbulence

Fellow engineer Senior(LSE: SNR) suffered no such woes on Monday, the stock last dealing 10% higher from last week's close.

Senior's half-year report released today showed revenues 4% higher, to £450.5m. This couldn't stop adjusted pre-tax profit slumping 19% during January-June, however, to £42.3m.

Senior advised that "business conditions deteriorated in the Flexonics division and resulted in a weak first half as end markets remained challenging with no clear signs of recovery yet visible."

Difficulties in the oil and gas segment are likely to keep the pressure on at Flexonics, Senior advised, although the firm's bullish take on the aerospace market remains intact. Indeed, the FTSE 250 play commented that "the outlook for the large commercial aerospace sector is both strong and visible."

Today's share price surge leaves Senior on a P/E rating of 14 times for 2016. So while I expect rising aircraft production to deliver splendid long-term gains, the poor condition of Senior's other end markets leave plenty of question marks over when earnings will bounce higher again. I reckon cautious investors should sit on the fence for the time being.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.