The length controllable synthesis and near-infrared photoluminescence of one-dimensional ternary Cu4Bi4S9 semiconductor nanobelts

• We obtained the 1 cm long one-dimensional ternary Cu4Bi4S9 nanobelts.
• We can control the Cu4Bi4S9 nanobelts length by tuning the solvent and reaction temperature.
• The Cu4Bi4S9 nanobelts can show a broad IR photoluminescence band at 77 K.
• The ab initio energy band calculation indicates small span between its direct band edge and indirect band edge.
• The photoluminescence has relation to the mixing band between direct band and indirect band near band edge.

The ternary Cu–Bi–S based semiconductor with abundant and environmental-friendly elements may provide alternative choice for near-infrared (NIR) light-emitting sources. High-quality copper bismuth sulfide Cu4Bi4S9 (CBS) nanobelts of controllable lengths up to 1 cm were synthesized through a modified solvothermal route by using solvents of varied boiling points (BP) and changing reaction temperatures (RT) to control the competition of efficient collision of Cu4Bi4S9 seeds, intermediate species and precursors and growth of Cu4Bi4S9 nanobelts. Their NIR photoluminescence (PL) of Cu4Bi4S9 nanobelts was firstly observed in the range of 1400–2200 nm, which showed the transition characteristics of mixed direct and indirect-bands nearby. The absorption and PL spectral data could be well accounted for by the ab initio band calculations of Cu4Bi4S9.

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