Sam Zhu may live and work in the Big Apple, but his pastime is dabbling in business opportunities in China.

At the height of China's economic boom, Zhu was able to take the small fortune he made running his Manhattan silk garment company, Fashion River, and plow it into numerous side investments in his native land. The projects he pursued in his spare time included real estate, a partnership in a hotel development company and co-founding a software company targeting manufacturers and importers.

Since China's economic slowdown, however, Zhu has mostly left those extracurricular activities. He said he now concentrates on promoting contemporary Chinese painting for the global auction market, while continuing his efforts to build Fashion River into a prominent brand name.

"You have to keep changing, looking for new opportunities to make business work," Zhu said. "That's my way."

Economic slowdowns in both China and the United States have forced US-based Chinese entrepreneurs like Zhu to rethink their plans for putting money earned in the states into projects in China. Years ago, when China was seeing double-digit economic growth, it was not out of the question for Chinese expats to parlay profits from one kind of business into a completely different business, sometimes with great success.

But John Wang, president of the Asian American Business Development Center in Manhattan, says economic concerns appear to have reduced the number of Chinese entrepreneurs who were applying the lessons they learned in the US to the opportunities they saw in their homeland.

"It's not happening as much," Wang said.

It would be an oversimplification, he cautioned, to blame a drop-off in investment in China by US-based Chinese entirely on economic worries. Doing business in China is a complex undertaking at the best of times, owing to myriad cultural, regulatory, and systemic issues, Wang said.

"It takes a while to get accustomed to (the China) market," he said.

By comparison, he said, the US has "a well-established structure, laws and regulations". In China, he added, "those are sometimes not as well established, so you have a lot of fluid situations that make it difficult for people to know exactly what they need to do".

Sometimes, Wang said, a business failure in China "has less to do with the economy" than "whether (a prospective entrepreneur is) able to navigate the system".

Nevertheless, the growth slowdown in both countries accompanies a decline in the rate of foreign direct investment in China from the US. In 2012, US-originated FDI in China slowed for the first time since 2009, despite rising 4.5 percent in 2011. Overall, total FDI in China totaled $111.7 billion in 2012, down from a record $116 billion in 2011, according to statistics published by China's Ministry of Commerce. In 2012, China's GDP growth was 7.8 percent - the slowest annual pace since 1999 - down from 9.3 percent in 2011.

Although FDI is a relatively minor contributor to China's overall capital flows compared with exports, some observers have seen the cooling FDI growth as a sign of waning investor enthusiasm for deals in emerging markets. But China still managed to "vastly outperform" other nations last year in attracting FDI, according to New York-based economic research company Rhodium Group.

"China is still hugely attractive to foreign investors," Rhodium said in a recent report.

In 2006, in a story on New York-based Chinese entrepreneurs, Crain's New York, a business magazine, quoted Zhu as comparing the abundance of wealth-generating opportunities in China to "a gold rush". At the time, China's GDP was 9.5 percent. That was five years before growth began to slow in 2011 and finally hit bottom around September 2012.

The article noted that Zhu managed to build Fashion River into a company with annual revenue of $100 million in just 14 years. At the time, the article said, he often returned from trips to Fashion River's trading office in Nantong, Jiangsu province, with "another small building to add to his property portfolio." Zhu eventually formed Jiangsu Zongyi, a property investment and development company, in partnership with a Chinese businessman. The pair built an extended-stay hotel with 350 suites in Nantong, but Zhu took his share of the profit from the sale of the building and moved on. He said in the interview that he believes real-estate prices in China are peaking, reducing opportunities for investors to realize big profits.

Zhu's dabbling also included becoming a part-owner of Nang Da Software, a company - since sold off - that develops enterprise-management software mainly for manufacturers and importers in China.

"I still see lots of opportunities in China," Zhu said recently. "But we have a much brighter future in art. A lot of people love Chinese art."

Last year's downturn in the art market in China represented "a good time" to move into the auction trade, Zhu said. Until 2012, the value of art and antiques sold at auction in China had been surging for three years. But the cooling economy and other factors sliced into sales at major auction houses on the Chinese mainland and in Hong Kong.

Married with one son who is a Hong Kong-based investment banker with Morgan Stanley, Zhu, a resident of Fort Lee, New Jersey, said he has no plans to move back to China. A naturalized US citizen, he said he feels "lucky" to be able to speak both Chinese and English, "so I can explore opportunities in the two biggest countries in the world".

He says he believes strongly in China's swing to a consumer-driven economy from one powered by exports.

"For the past 30 years, China has been growing," he said. "But now it can't expand the way it did before, so it has to grow internally. If China can't make the transition smoothly, it will have a hard landing."

But if it completes the transition, he said "it can still grow, "just not as fast as in past years".