The single particle emission behaviours of our previously reported excitation-dependent full-colour carbon dots (F–C dots) have been analyzed by a single-particle fluorescence imaging technique. The co-localization of the F–C dots excited with different wavelengths shows that single F–C dots can also be excited with multiple energies. The co-localization of the F–C dots that emit at different colour regions under the same excitation wavelength or different excitation wavelengths shows that single F–C dots have a broad emission band from blue to red, but the emission intensities in different colour regions vary from one particle to another. So this study concretely proves that the full colour emissions are single particle behaviours; they are different from the other type of excitation dependent full-colour emission carbon dots whose full-colour behaviour originates from the large heterogeneity in both particle size and the structures of the ensemble. Then the origination of the full-colour emission at the single dot level was further studied by comparing the emission properties of the F–C dots and the small molecular byproducts, and it is found that the emissions of the dozens of molecular byproducts can also cover the full visible regions. And the emission positions of F–C dots are very similar to those of the byproducts at the same excitations, but they show different lifetimes. So a mechanism for the full colour emissions of F–C dots is proposed to originate from the hybridization of multiple small emissive molecules on the emissive carbon cores. This single particle level understanding of full-colour emission properties will pave the way towards the development of single dot imaging or tracking.

The interaction forces between carbohydrates and lectins were investigated by single-molecule force spectroscopy on both cancer and normal cells. The binding kinetics was also studied, which shows that the carbohydrate–lectin complex on cancer cells is less stable than that on normal cells.

Galactose was detected and localized on the surface of cancer and normal cells by topography and recognition imaging at the single molecular level. There are more galactoses on cancer cells than on normal cells. The stability of galactose–lectin on cancer cells is much lower than that on normal cells.

We used single molecule force spectroscopy (SMFS) to investigate the interacting force between single cysteine and amino acid transporters in eukaryotic cell membranes. We measured the transporting force of cysteine and found that its conformation on the AFM tip is important for discriminating the substrate in the transporting pathway.

We used in situ atomic force microscope (AFM) to explore the exquisite structure of mitochondrial membranes under quasi-native conditions. The outer surface of the mitochondrial membrane is slightly rough and protein-embedded inside, while the inner mitochondrial membrane is smooth in the intermembrane space surface and protein-covered on the matrix side.

We applied force spectroscopy based on atomic force microscope (AFM) to demonstrate the possibility of measuring the interaction force between single quantum-dots (QDs) and living cells at single particle level under native conditions. In the force–distance cycle, we recorded the events of cellular uptake of single QDs and single QD detachment from the cell.

Herein we investigate the size-dependent force of endocytosing single gold nanoparticles by HeLa cells. The results reveal that both the uptake and unbinding force values are dependent upon the size of gold nanoparticles.

Band III is a key protein for the structure and function of red blood cell membranes. To date, the distribution and morphology of Band III in cell membranes is still unclear because of limited approaches. We applied Topography and RECognition imaging microscopy (TREC), which extends the application of atomic force microscopy (AFM) to recognize a single molecule in a biological complex, to visually locate a single Band III protein in quasi-native cell membranes by anti-Band III-functionalized AFM tips under physiological conditions. The Band III proteins are well distributed in the inner leaflet of cell membranes. The height of the whole Band III protein in cell membranes is in the range of 9–13 nm. The unbinding force between Band III in the membrane and anti-Band III on the AFM tip is about 70 pN with the loading rate at 40 nN/s. Our result is significant in revealing the location and morphology of Band III in the inner cell membrane at the molecular level.

Studies of cell membrane structure by atomic force microscopy (AFM) have been limited because of the softness of cell membranes. Here, we utilize a new technique of sample preparation to lay red blood cell membranes on the top of a mica surface to obtain high resolution images by in-situ AFM on both sides of cell membranes. Our results indicate that the location of oligosaccharides and proteins in red blood cell membranes might be different from the current membrane model. The inner membrane leaflet is covered by dense proteins with fewer free lipids than expected. In contrast, the outer membrane leaflet is quite smooth; oligosaccharides and peptides supposed to protrude out of the outer membrane leaflet surface might be actually hidden in the middle of hydrophilic lipid heads; transmembrane proteins might form domains in the membranes revealed by PNGase F and trypsin digestion. Our result could be significant to interpret some functions about red blood cell membranes and guide to heal the blood diseases related to cell membranes.

Na+−K+ ATPases have been observed and located by in situ AFM and single molecule recognition technique, topography and recognition imaging (TREC) that is a unique technique to specifically identify single protein in complex during AFM imaging. Na+−K+ ATPases were well distributed in the inner leaflet of cell membranes with about 10% aggregations in total recognized proteins. The height of Na+−K+ ATPases measured by AFM is in the range of 12−14 nm, which is very consistent with the cryoelectron microscopy result. The unbinding force between Na+−K+ ATPases in the membrane and anti-ATPases on the AFM tip is about 80 pN with the apparent loading rate at 40 nN/s. Our results show the first visualization of an essential membrane protein, Na+−K+ ATPase, in quasi-native cell membranes and may be significant to reveal the interactions between Na+−K+ ATPases and other membrane proteins at the molecular level.

Band III is a key protein for the structure and function of red blood cell membranes. To date, the distribution and morphology of Band III in cell membranes is still unclear because of limited approaches. We applied Topography and RECognition imaging microscopy (TREC), which extends the application of atomic force microscopy (AFM) to recognize a single molecule in a biological complex, to visually locate a single Band III protein in quasi-native cell membranes by anti-Band III-functionalized AFM tips under physiological conditions. The Band III proteins are well distributed in the inner leaflet of cell membranes. The height of the whole Band III protein in cell membranes is in the range of 9–13 nm. The unbinding force between Band III in the membrane and anti-Band III on the AFM tip is about 70 pN with the loading rate at 40 nN/s. Our result is significant in revealing the location and morphology of Band III in the inner cell membrane at the molecular level.

Galactose was detected and localized on the surface of cancer and normal cells by topography and recognition imaging at the single molecular level. There are more galactoses on cancer cells than on normal cells. The stability of galactose–lectin on cancer cells is much lower than that on normal cells.

We used single molecule force spectroscopy (SMFS) to investigate the interacting force between single cysteine and amino acid transporters in eukaryotic cell membranes. We measured the transporting force of cysteine and found that its conformation on the AFM tip is important for discriminating the substrate in the transporting pathway.

Herein we investigate the size-dependent force of endocytosing single gold nanoparticles by HeLa cells. The results reveal that both the uptake and unbinding force values are dependent upon the size of gold nanoparticles.

We applied force spectroscopy based on atomic force microscope (AFM) to demonstrate the possibility of measuring the interaction force between single quantum-dots (QDs) and living cells at single particle level under native conditions. In the force–distance cycle, we recorded the events of cellular uptake of single QDs and single QD detachment from the cell.