Facile synthesis of nano-sized CuFe2S3: morphology and diverse functional tuning and crystal growth mechanism exploring

Abstract Ternary chalcogenide compounds are such promising and have been used for much practical applications. As a sort of these compounds, cubanite (CuFe2S3) possess some unique properties which can be used in different fields. In our study, we developed a facile one pot synthesis of CuFe2S3 nanocrystals (NCs) at a low reaction temperature, and achieved a morphology and phase composition tuning of the NCs through changing a variety of precursors and surfactants, meanwhile improved their magnetism and optical properties. Eventually, well-ordered and ‘nano-brick’ like CuFe2S3 NCs were obtained and showed best magnetism and near-infrared fluorescence properties. Furthermore, the NCs were proved with good biocompatibility and possibility for cell labeling. This kind of materials with lower toxicity and potential of magnetic is bound to remedy the defects of photoluminescence quantum dots (QDs) and be with higher potential in the field of biological diagnosis and multi-functional system construction.


Introduction
Ternary chalcogenide compounds have attracted an extensive attention owe to their unique physical and chemical properties, such as magnetism and photoelectric properties [1][2][3][4][5][6][7]. Furthermore, with near-infrared fluorescence and low toxicity, ternary luminescence nano-materials also have shown great potential as an alternative to the traditional binary quantum dots in the field of bioimaging and multifunctional system construction [8,9]. Among them, ternary copper iron sulfide compounds such as chalcopyrite and cubanite (CuFe 2 S 3 ) are unique candidates, owing to their good biocompatibility and magnetism potential. However, to the best of our knowledge, the majority of former reports usually focus on the crystal and electronic structure of chalcopyrite, and only a few reports referred the synthesis of CuFe 2 S 3 [10][11][12][13].
Natural mineral CuFe 2 S 3 has been acknowledged to be with orthorhombic structure [14][15][16], in which the cations are tetrahedrally coordinated by S atoms, forming an approximately hexagonal packing. The Fe 2þ and Fe 3þ ions share the adjacent edges of tetrahedral and there is a rapid electron transfer between them [17,18]. However, in the previous reports, it has been proven that the CuFe 2 S 3 will transform to a cubic form at high temperature [19][20][21]. The crystal structure of this cubic CuFe 2 S 3 is based on a cubic close-packed matrix of sulfur atoms, wherein the metal atoms are located in the tetrahedral interstices, furthermore, the ferrous, iron and cuprous ions are randomly distributed on these cation sites [15,20]. This special structure endows cubic CuFe 2 S 3 with unique photoelectricity and magnetic properties, which play a crucial role in biological application. However, most of the existed reports on CuFe 2 S 3 are about crystal in bulk, either using naturally existing or synthetic single crystal or polycrystalline compounds. There have been very few studies on the synthesis and characterization of nano-sized crystalline CuFe 2 S 3. More studies are further needed to investigate not only the synthesis but also the modulation of CuFe 2 S 3 crystal morphology, luminescence and magnetic properties. In most cases, the synthesis of CuFe 2 S 3 usually needs strict condition with a high temperature exceeding 200 C. Therefore, it is a challenge to develop a facile and mild strategy for fabricating nano-sized CuFe 2 S 3 under laboratory conditions and study their prospect in biological application.
In this study, CuFe 2 S 3 NCs with uniform and small size, as well as magnetism and near-infrared fluorescence properties would be prepared. A facile and mild strategy to fabricate CuFe 2 S 3 NCs under a lower reaction temperature (180 C) was developed. Meanwhile, the morphology and physical properties of these NCs have been finely modulated by changing the reactants. Furthermore, cubic CuFe 2 S 3 NCs with magnetism and near-infrared fluorescence properties showed great potential application on cell labeling. Our work is bound to encourage further exploration in the synthesis of nanosized CuFe 2 S 3 under laboratory conditions and expand their multifunctional application in the biological field. Synthesis of CuFe 2 S 3 nanocrystals (CuFe 2 S 3 NCs) CuFe 2 S 3 NCs were prepared through a one pot method. The device diagram of experimentation is shown in Fig. 1. For a typical synthesis, 0.1705 g CuCl 2 Á2H 2 O and 0.2703 g FeCl 3 Á6H 2 O were added into a mixture of 12 ml OA and 18 ml DT in a 100 ml three-necked round-bottom flask. The flask was put into a constant temperature heating magnetic stirrer with oil bath heating (140 C) under N 2 flow until reactants were fully dissolved. The S-precursor suspension was freshly prepared by mixing 0.1522 g of thiourea with 6 ml of DT under magnetic stirring in air and preheated to 100 C. Next, the S-precursor solution was transferred into a syringe (equipped with a large needle) and injected quickly into the flask at 140 C. The temperature of mixture was further quickly raised to 180 C and kept for 15 min. To terminate the reaction, the flask was quickly transferred to a cold-water bath. The resulting nanocrystals were separated from the dispersion solution by centrifugation (4000 rpm, 5 min) and washed by ethanol for several times to remove the impurities. The obtained products were dispersed in absolute ethanol for further characterization.

Reagents and materials
In order to achieve the structure and morphology modulation, and further optimize the luminescence and magnetism properties of CuFe 2 S 3 NCs, different iron and copper precursors, sulfur sources and surfactants were chosen in the following experiments. The detailed preparation conditions are shown in Table 1.

Material characterization
X-ray diffraction (XRD): The prepared samples were dried in a drying oven under 70 C, and the crystalline structure were measured on an X-ray diffractometer (Panalytical Empyrean), at 45 kV and 40 mA, for monochromatized Cu Ka (k ¼ 1.5418 Å ) radiation.
Raman spectra (RM): The Raman spectrum of dry sample was recorded on a Confocal Laser MicroRaman Spectrometer (LABRAM-HR) with 514.5 nm radiations from a 10 mW argon ion laser at room temperature.
X-ray photoelectron spectroscopy (XPS): The samples were redispersed in absolute ethanol with a sufficient ultrasonic oscillating, then dropped on a silicon slice. The XPS measurements were carried out on a Kratos Axis Ultra DLD spectrometer equipped with a monochromatic Al Ka X-ray source.
Transmission electron microscope (TEM): The samples were redispersed in absolute ethanol under sufficient ultrasonic oscillating, then dropped on a copper net coating with a carbon film. The morphology and microstructure of CuFe 2 S 3 NCs were monitored using high-resolution transmission electron microscopy (HRTEM) on TecnaiG2F20S-TWIN microscope at 200 KV.
Magnetism measurement: The magnetic measurements of dry CuFe 2 S 3 NCs were performed by using a superconducting quantum interference magnetometer (MPMS-XL-7, Quantum Design) at both room temperature (300 K) and low temperature (3 K).
Photoluminescence characterization: The samples were dispersed in absolute ethanol with a sufficient ultrasonic oscillating, then 1 ml of the solution was taken. The fluorescence emission of CuFe 2 S 3 NCs was collected by using a fluorescence spectrometer (F-7000, Hitachi), using an emission wavelength at 500 nm.

Potential application of CuFe 2 S 3 NCs
Cytotoxicity study: The cytotoxicity of CuFe 2 S 3 NCs against human osteosarcoma cell line MG63 cells was studied using standard methyl thiazolyltetrazolium (MTT, Sigma Aldrich) assay. MG63 cells were dispensed onto a 24-well plate at a density of 1 Â 10 4 cells per well. After culturing 24 h for cell attachment, the media were taken out from the wells, followed by washing three times with PBS, and then incubated with various concentrations of CuFe 2 S 3 NCs (30, 90 and 150 mg/mL). After further incubation for 1, 3 and 5 d, the solutions were changed with fresh DMEM culture medium, cell viability was studied by standard methyl thiazolyltetrazolium assay.
Cell labeling: The cell-labeling capacity of CuFe 2 S 3 NCs was investigated as follows: MG63 cells were seeded onto a 24-well plate at a density of 3 Â 10 4 cells per well in a 24-well plate, and cultured in the culture box (CO 2 5%, 37 C) for 24 h before adding the NCs. After cell attachment, the media were taken out from the wells, followed by washing three times with PBS. Cells were then incubated with CuFe 2 S 3 NCs at a certain concentration (150 mg/mL) for 30 min. After cells were washed carefully using PBS to wipe off uninternalized nanoparticles and incubated for another 30 min, a confocal laser scanning microscopy (CLSM; LeicaSP5, Leica Microsystems, Germany) was acquired for cell imaging.

Phase and chemical characterization
The phase composition of the samples was examined using XRD. As shown in Fig. 2a, the XRD spectra of S1, S2 and S3 have almost similar diffraction patterns which are corresponded to the orthorhombic CuFe 2 S 3 (ICDD card, No. 65-1323), indicating the fabrication of relatively pure CuFe 2 S 3 NCs with an orthorhombic structure by our facile and mild method. The sharp peaks and low background observed in S2 and S3 suggest a higher crystallinity of S2 and S3 than that of S1 with relative diffusion background. Contrarily, S4 and S5 show three different intense peaks at 2h ¼ 29.2 , 48.6 and 58.7 which are attributed to the cubic CuFe 2 S 3 phase, oriented along the [111], [220] and [311] crystal planes, respectively [16]. These results indicate the successfully synthesis of cubic CuFe 2 S 3 NCs, according to the standard spectra of cubic CuFe 2 S 3 (ICDD card, No. 81-1378). Furthermore, compared with S1-S3, S4 and S5 presented relative disordered peaks which reveal a relative low crystalline of the samples, meanwhile S5 was with higher crystallinity than S4. These results reveal that nano-sized crystalline CuFe 2 S 3 could be fabricated using our one pot method at a relative low temperature (180 C). The crystal structure of NCs could be adjusted from orthorhombic to cubic by controlling the reactants, surfactants and reaction conditions. Figure 2b shows the Raman spectrum of CuFe 2 S 3 nanocrystals of S5 at room temperature. According to the standard spectrum of cubic CuFe 2 S 3 , the stronger peak (290 cm À1 ) and three weaker peaks (frequency 169, 323 and 355 cm À1 ) are in good agreement with the standard spectrum, indicating that a relatively pure cubic CuFe 2 S 3 has been obtained.
To further understand the nature of interactions among the atoms in product we have prepared, XPS measurements were undertaken. The XPS survey spectrum of the S5 NCs is shown in Fig. 2c, and the photoelectron peaks of Fe 2p is presented in Fig. 2d. In the survey and high-resolution spectra of S5, C 1 s (fitting element), Si 2 s and Si 2p peaks (silicon substrate) are also observed with the exception of the expected Cu 2p, S 2p and Fe 2p peaks. After peak fitting, four peaks appear in the high-resolution spectrum of Fe 2p, and two peaks appear at 711 and 725 eV, which can be attributed to the ionization of Fe 2p 3/2 and Fe 2p 1/2 electrons of Fe 2þ , furthermore it displays another two peaks at 714 and 726 eV corresponding to Fe 2p 3/2 and Fe 2p 1/2 electrons of Fe 3þ , respectively. These parameters almost coincide with the Fe 2þ and Fe 3þ surface species in the previous reports [22,23]. Figure 3 displays the HRTEM images of the NCs of S1-S5, and insert maps show the enlarged images accordingly. As the images illustrate, the crystal morphology of samples varied from spherical to 'brick' like with the varying of the reaction precursors and surfactants from S1 to S5. Generally, the crystals of S1, S2 and S3 are all spherical-like nanocrystals with the average crystal sizes about 3, 4 and 4 nm, respectively ( Fig. 3a-c). S2 and S3 show a relatively lower dispersity than S1. Furthermore, Fig. 3d and e shows that S4 and S5 have completely different crystal morphology in comparison with S1-S3. For S4, a mixed crystal morphology of spherical and 'brick' ones are presented. The diameter of spherical one is about 7 nm, while size of brick-like crystal is about 20 nm. The HRTEM imagine in Fig. 3d reveals that part of the lattice fringes of crystals could be observed. The brick-like ones have a better sharp fringe, and their crystal parameters are coincided with the cubic CuFe 2 S 3 as well. In addition, for S5, all the NCs are of the shape of 'brick' and selfassemble in a certain orientation (Fig. 3e). These monodispersed nano-bricks are of 4 nm width and 8 nm length, and the distance between the nano-bricks are nearly the same about 2-3 nm. The enlarge scale of Fig. 3e clearly shows that each nano-brick has uniform morphology and good monodispersity. The lattice fringes of the crystals can be clearly seen with a lattice space about 3.05 Å between two adjacent lattice planes, which is consistent with the (111) plane (Fig. 3f) of cubic CuFe 2 S 3 NCs, indicating that the crystallinity of S5 is much higher than S4.

Magnetic characteristics of the CuFe 2 S 3 NCs
The magnetism of the NCs was characterized by a superconducting quantum interference magnetometer, and the field-dependence magnetization curves M(H) are shown in Fig. 4. Under room temperature, all the NCs showed no magnetism (so that the data not shown here). Figure 4a-e shows the magnetization curves at 3 K of S1-S5, and the obvious coercivity could be observed in all the NCs, indicating the well magnetic property of CuFe 2 S 3 NCs at low temperature. Furthermore, S4 and S5 show relatively higher magnetism than S1-S3, while S5 has the highest magnetism. These results indicate that the magnetism of CuFe 2 S 3 NCs is dependent on the temperature. At low temperature, the whole NCs we synthesized possess the magnetism, and S5 shows the strongest magnetism among them all.

Fluorescent characteristics of the CuFe 2 S 3 NCs
The near-infrared fluorescence properties of CuFe 2 S 3 were then studied. As shown in the PL emission spectra (Fig. 5), when the NCs were irradiated at 500 nm, a strong red emission peak at 614 nm and a weaken emission peak at about 715 nm were observed for all the NCs. The full width at half maximum (FWHM) of these two peaks are the same about 40 nm. Furthermore, the fluorescence intensity of the NCs increased with the order from S1 to S5, and S5 shows the strongest emission about 10 times than that of S1. These results demonstrate that the near-infrared fluorescence intensity of CuFe 2 S 3 NCs varied with different precursors and reaction conditions. By judicious modulating the synthesis process, CuFe 2 S 3 NCs with near-infrared emission would be obtained and show great potential for bioimaging.

Potential evaluation of CuFe 2 S 3 nanocrystals in bioimaging
Due to the stronger fluorescent intensity compared with other samples, S5 was chosen to evaluate the potential application of CuFe 2 S 3 NCs in bioimaging. We first investigated their potential toxicity using human osteosarcoma cell line MG63 cells. For cytotoxicity test, MG63 cells were incubated with CuFe 2 S 3 NCs of S5 at different concentrations for 1, 3 and 5 d, and the corresponding cell viability data were obtained by MTT assay. As shown in Fig 6a, the cells in all the groups proliferated dramatically along with time prolonged, although the samples incubated with NCs presented a little lower cellular survival than the control after 1 d of incubation. There is little difference in the percentage of viable cells between the experimental and control samples even at the highest concentration of 150 lg/mL in the following days, which suggested excellent cytocompatibility of the prepared CuFe 2 S 3 NCs.
Encouraged by the strong near-infrared fluorescence and biocompatibility of the prepared CuFe 2 S 3 NCs, we further investigated the potential of the prepared CuFe 2 S 3 NCs for cell imaging. MG63 cells were first incubated with CuFe 2 S 3 NCs of S5 for 30 min to label the cells, then the near-infrared fluorescence of intracellular NCs was observed by CLSM. Figure 6b is the fluorescent field of MG63 cells incubated with S5, compared with the bright field (Fig. 6c) of that. As CLSM images show, a red fluorescence signal can be  observed inside the cells in Fig. 6b. Furthermore, the red fluorescence of CuFe 2 S 3 NCs is homogeneously distributed in the cytoplasm instead of the cell nucleus. These results indicate that the prepared CuFe 2 S 3 NCs with near-infrared fluorescence could penetrate into the living cells and be utilized for cell imaging.

Discussion
As a typical representative of ternary chalcogenide compounds, CuFe 2 S 3 with near-infrared fluorescence and good biocompatibility has attracted much attention in the field of photoelectricity and biomedical research. However, studies on the controllable synthesis of nanoscale CuFe 2 S 3 are rarely reported. The above results demonstrate that nano-sized CuFe 2 S 3 have been successfully fabricated using a facile and mild one pot synthesis approach. Most importantly, the phase composition, morphology and physical properties of prepared NCs can be modulated by changing the precursors and surfactants. Finally, CuFe 2 S 3 NCs with good biocompatibility and near-infrared fluorescence has been proved to be potential for cell imaging.

Growth mechanism of CuFe 2 S 3 NCs based on reactants tuning
The possible growth mechanism is schematically illustrated in Fig. 7. Generally, the reactants of metal precursors, specific reducers and surfactants were mixed in the organic solvent to produce free Cu 2þ and Fe 3þ , meanwhile some of these metal ions would be reduced to Cu þ and Fe 2þ by the reducer in the system. At predetermined heating temperature, well-preheated S precursor was added, then S 2ions were released and reacted with the free copper and iron ions in the solution, inducing a break precipitation of copper, iron and sulfur ions to form enormous CuFe 2 S 3 nuclei [24]. Thanks to the strong surface activity, the free surfactant molecules in the solvent were probably to be attracted on the surface of the nuclei [25]. With continuous heating, the growing of the nuclei progressed with more free metal and sulfur ions continuously migrating to the surface of the nuclei. At the same time, the ions exchange and atom rearrangement both happened inside and on the surface of the crystals [26], resulting the variation of the crystal morphology, size, composition and crystallinity, until the stable CuFe 2 S 3 NCs were formed. Obviously, the growth of CuFe 2 S 3 NCs can be affected by the followings: (1) the nucleation and growth of CuFe 2 S 3 nuclei are dependent on the producing speed of the free copper, iron and sulfur ions by reactants [27][28][29], (2) the ion exchange and atom rearrangement during crystal growth are affected by the properties of surfactant or solvent. Therefore, the phase composition and crystal morphology of CuFe 2 S 3 NCs can be judiciously modulated under varied conditions. As revealed in above results, although with different reactant precursors and surfactants, all the samples from S1 to S5 are pure CuFe 2 S 3 NCs, suggesting the correctness of the proposed crystal growth mechanism and the efficiency of our one pot approach to prepare CuFe 2 S 3 NCs. The totally different phase and crystal morphology of S4 and S5 compared with S1 to S3 should be mainly attributed to the varied conditions in the growth processes, including the metal precursors, surfactants and sulfur sources. First, the effect of metal precursors and varied S source on phase composition was revealed. As Fig. 2a-c shows, S1, S2 and S3 have the same phasic structure with similar spherical-like morphology. Comparing their respective reaction conditions in Table 1, it is easily inferred that different metal precursors (for S2 and S3) and varied S source (for S1 and S2) are not the decisive factors to affect crystal morphology and phase structure.
Second, the effect of the varied surfactants attributed to the differences in the crystal dispersity and size was studied. Although with similar phase composition in S1, S2 and S3, S1 showed a better particle dispersity, smaller crystal size and lower crystallinity than S2 and S3. Comparing the reactants, it can be inferred that the reaction using DT as surfactant (for S1) is inclined to produce smaller nanocrystals with better dispersity than the reaction using ODE þ OAM as surfactants (for S2 and S3). With shorter molecular length and higher polarity, DT is more likely to move to the nuclei and bind with cations on the nuclei surface [30]. Therefore, DT molecules were more evenly distributed on the surface of CuFe 2 S 3 nuclei, which in turn protect the nuclei from aggregation and restrict the continuous growth of crystals, producing the CuFe 2 S 3 NCs with better dispersity, smaller size, but lower crystallinity.
In the following experiments, the combination using of DT as surfactant and thiourea as S source in S4 and S5 resulted in great change in crystal growth progress and the phase composition of final crystals. As above results show, S4 and S5 have the phase composition of cubic CuFe 2 S 3 and brick-like crystal morphology, which were totally different with S1 to S3. This phenomenon may be explained as follows: Both DT and thiourea are strong reducers which resulted in supplying more Cu þ , Fe 2þ and S 2À in the system [31]. Therefore, in comparison with the S1 using DT as reductant and surfactant, DDTC as S source, and compared with S2 and S3 using thiourea as S source, ODE as reductant, there are more free ions for the deposition of ternary sulfide in S4 and S5. It should be noted that both the protection of DT and the selection of SH-on crystal orientation have significant impacts on the growth habit of nanocrystal [32,33], resulting in great change of phase composition and crystal morphology in the final products. On one hand, as above mentioned, DT with shorter molecular length moves easier to nuclei surface to form binding on the surface, on the other hand, it has been reported that such cations (Cu þ , Fe 2þ , Fe 3þ ) are especially sensitive to the sulfhydryl to form complexation, it would reduce not only the surface tension and surface energy but also the growing rates of each crystal planes, inducing the thoroughly change of crystal growing habit and crystal structure [34][35][36][37][38]. Therefore, the NCs in S4 and S5 would prefer to grow uniaxially along a few of the lattice planes, and formed the cubic CuFe 2 S 3 with brick-like morphology. Furthermore, as the reduction reactions and change of surface planes growth rates are both energy required [39], meanwhile the motion rates of molecule and ions were slower at low temperature (90 C), S4 of adding S sources at lower temperature showed an incompletely change of crystal growth, forming lower crystalline cubic CuFe 2 S 3 with mixing structure morphology of sphere-like and brick-like ones, as well as aggregated crystals. On the contrary, in S5 of combing DT and thiourea as at higher temperature (140 C), uniform and small CuFe 2 S 3 with cubic structure were formed. Furthermore, this special habit of crystal growth is more or less to affect the atomic rearrangement, resulting in the reducing of crystallinity or leading to the formation of defects in crystals, thus S5 showed a relative lower crystallinity than S1 to S3.
The ordered arrangement of the brick-like crystals of S5 is related to their magnetism. As Fig. 4 shows, all the samples have obvious magnetic behavior at low temperature (3 K), especially S4 and S5 with cubic structure show higher magnetism, and the magnetism of S5 is the strongest. The strongest magnetism of S5 contributes to the lining of the single nano-brick with well-ordered alignment, in return this ordered alignment is possible to enhance the magnetism.

The magnetism of CuFe 2 S 3 NCs
The magnetism of CuFe 2 S 3 mainly originates from the varied valence state of Fe atoms, as the copper ions in this compound are in the diamagnetic Cu þ (3d 10 ) state [40]. The varied valence state of Fe atoms has also been proved by the XPS analysis above. Previous reports of Mö ssbauer spectra of CuFe 2 S 3 NCs have shown that at room temperature the iron ions are in non-magnetic state [18]. However, at lower temperature, the cubic CuFe 2 S 3 phase CuFe 2 S 3 have stable charges of Fe 2þ and Fe 3þ in the tetrahedral sulfur sites, along with electron exchange between these ions, so the magnetization is observed [41]. Furthermore, as above discussed, S4 and S5 with more Fe 2þ produced by stronger reduction would accelerate atomic exchange and varied ratio of two valences stated iron ions, resulting in stronger magnetism. Another reason for the producing of magnetization is the presence of Fe-S type of magnetism impurities in the CuFe 2 S 3 crystals [42]. It has been discussed above, more S 2produced and reduction of Fe 3þ to Fe 2þ by DT and thiourea, hence, some non-stoichiometric precipitates might be produced and resulted in some Fe-S type of magnetism impurities in S4 and S5. Meanwhile, the more through change of crystal growth habit in S5 might lead to more crystal defect, resulting in the strongest magnetism of S5.

Luminescence mechanism of CuFe 2 S 3 NCs
Similar with typical ternary sulfide such as CuInS 2 , the PL emission of CuFe 2 S 3 NCs are also related to defect concentration.  As schematically described in Fig. 8, in the ternary nano-crystalline band gap, there are many donor-acceptor states, usually from internal crystal defects [43][44][45][46]. Generally, the S vacancy and Cu interstitial ions act as the donors, while Cu vacancy and Fe interstitial ions act as the acceptors in the nanocrystals. When the Cu ions occupy the sites of Fe ions, or Fe ions occupy the positions of Cu ions, inverse defects are formed. Consequently, the excitons generated by the light absorption of CuFe 2 S 3 NCs transform to these donoracceptor-pair (DAP) defect states and recombine to give out emissions [47]. The enhanced luminescence from S1 to S5 should be related to the growing habit of the varied samples. Comparing with other samples, there is more obviously crystal deformation and defects in S5, due to the inhibitation of some crystal growth and atomic rearrangement, and this phenomenon results in a higher fluorescence emission.
These results reveal that by judiciously changing the composition of reactants and reaction conditions, uniform nano-sized cubic CuFe 2 S 3 with near-infrared emission and magnetism could be obtained. The following cellular experiments proved that CuFe 2 S 3 NCs have good biocompatibility and show great potential for cell labeling. The further application of this material to construct multifunctional system would be expected.

Conclusions
In summary, a facile and mild one pot synthetic route was developed to synthesis CuFe 2 S 3 NCs. Their phase composition and morphology, as well as magnetism and near-infrared fluorescence properties could be judiciously modulated by changing the precursors and surfactants. The mechanism related to these changes in physical and chemical properties were also discussed. The best magnetism and PL emission property are presented in cubic CuFe 2 S 3 NCs with 'nanobrick' like morphology and well-ordered arrangement. Furthermore, nano-sized cubic CuFe 2 S 3 was proved with good biocompatibility and near-infrared fluorescence properties, showing great potential for biological imaging. The synthesis of these nanoscale CuFe 2 S 3 NCs with tunable composition, morphology and multiple properties would open a new avenue for directing the preparation of ternary chalcogenide nanocrystals with dual functions.