Fig. 1. Single-molecule photoluminescence. (a) Schematic diagram of the experimental setup of photoluminescence. (b) Photon image of single ZnPc molecule. (c) Corresponding photon intensity profile. (d) Phototautomerization and visualization of H2Pc molecules. (e) Determination of the excitation lifetime of a single molecule in NCP through the time-dependent single-photon counting technique. [(a)–(c) Reproduced with permission from Ref. 11. Copyright 2020, Springer Nature Limited. (d) Reproduced with permission from Ref. 52. Copyright 2024, Springer Nature Limited. (e) Reproduced with permission from Ref. 53. Copyright 2024, American Chemical Society.]

Fig. 2. Single-molecule Raman imaging. (a) Schematic illustration of the SERS mechanism within metal nanoparticles. (b) Photodegradation of 4-nitrothiophenol based on SERS. (c) Catalytic reaction process of single rhodamine B isothiocyanate molecule. (d) Schematic illustration of the SERS for side-gating modulation. (e) SERS spectra of 1,4-benzenedithiol molecular junction at different gate voltages. (f) Schematic illustration of the experimental setup of TERS. (g) Characteristic peaks corresponding to the reaction product p,p′-dimercaptoazobisbenzene in the TERS spectra. (h) Raman images obtained at different Raman peak positions of single magnesium porphyrin molecule. [(a) Reproduced with permission from Ref. 65. Copyright 2019, American Chemical Society. (b) Reproduced with permission from Ref. 66. Copyright 2015, Royal Society of Chemistry. (c) Reproduced with permission from Ref. 67. Copyright 2020, American Association for the Advancement of Science. (d), (e) Reproduced with permission from Ref. 68. Copyright 2018, American Chemical Society. (f) Reproduced with permission from Ref. 69. Copyright 2013, Springer Nature Limited. (g) Reproduced with permission from Ref. 70. Copyright 2012, Springer Nature Limited. (h) Reproduced with permission from Ref. 71. Copyright 2019, Oxford University Press on behalf of China Science Publishing & Media Ltd.]

Fig. 3. Single-molecule electroluminescence based on STM. (a) Schematic diagram of STM-electroluminescence from a single ZnPc molecule on NaCl/Ag(100) substrate. (b) Spectral evolution from isolated ZnPc monomers to an artificially constructed molecular dimer. (c) Simultaneously acquired photon map (top) and STM image (bottom) of a 3×3 molecular array composed of ZnPc molecules. (d) Phosphorescence map of the 3,4,9,10-perylenetetracarboxylicdianhydride system. (e) dI/dV spectrum recorded at the center of a single quinacridone molecule. [(a), (b) Reproduced with permission from Ref. 72. Copyright 2016, Springer Nature Limited. (c) Reproduced with permission from Ref. 73. Copyright 2017, Springer Nature Limited. (d) Reproduced with permission from Ref. 74. Copyright 2019, Springer Nature Limited. (e) Reproduced with permission from Ref. 75. Copyright 2023, American Physical Society.]

Fig. 4. Single-molecule electroluminescence of graphene-based single-molecule devices. (a) Schematic illustration of single-molecule luminescent diode. (b) Superhigh-resolution image (top) and the polar diagram (bottom) of the single-molecule electroluminescence. (c) Counting of emitted photons for different wavelengths. (d) Optoelectronic joint detection of the graphene-based single-molecule devices. (e) Statistical histogram of the decay time of phosphorescent signals. (f) Schematic of the single-molecule devices used for the logic operation. (g) Construction of the full-adder. [(a)–(c) Reproduced with permission from Ref. 24. Copyright 2023, Wiley-VCH GmbH. (d)–(g) Reproduced with permission from Ref. 25. Copyright 2024, Elsevier Inc.]

Fig. 5. Photo-induced isomerization switching. (a) Photochemically induced isomerization process of diarylethylene molecule. (b) Schematic representation of the reversible switching of a single diarylethylene molecule device. (c) I−t curves of the molecule in its photo-induced open and closed ring states. (d) Schematic representation of the reversible cis-to-trans isomerization of azobenzene triggered by light irradiation. (e) Schematic representation of the reversible cis-to-trans isomerization of azobenzen-based single-molecule device. (f) Azobenzene single-molecule junctions featuring distinct side groups. [(a) Reproduced with permission from Ref. 83. Copyright 2011, American Chemical Society. (b), (c) Reproduced with permission from Ref. 84. Copyright 2016, American Association for the Advancement of Science. (d) Reproduced with permission from Ref. 90. Copyright 2013, Wiley-VCH GmbH. (e) Reproduced with permission from Ref. 91. Copyright 2019, Springer Nature Limited. (f) Reproduced with permission from Ref. 92. Copyright 2024, American Chemical Society.]

Fig. 6. Photo-conductance effects in single-molecule devices. (a) Schematic diagram of single porphyrin-C60 molecular junction. (b) Schematic representation of charge transport mediated by the HOMO. (c) Schematic representation of the charge transfer when an exciton is formed through photoexcitation. (d) A substantial shift in the electrode energy level in single imidazole molecular junction upon photon absorption. (e) Schematic representation of light-induced electron tunneling through frontier molecular orbitals. (f) Transmission spectra of the DPP molecular junction. (g) Coulomb stability diagram of a single C60 molecule transistor under THz irradiation. (h) Schematic demonstration of generating hot electrons in single 4,4′-bipyridine molecule junction. (i) Nonequilibrium distribution of hot electrons in a single-molecule junction. [(a) Reproduced with permission from Ref. 32. Copyright 2011, American Chemical Society. (b), (c) Reproduced with permission from Ref. 33. Copyright 2018, American Chemical Society. (d) Reproduced with permission from Ref. 97. Copyright 2021, Royal Society of Chemistry. (e), (f) Reproduced with permission from Ref. 99. Copyright 2023, Springer Nature Limited. (g) Reproduced with permission from Ref. 34. Copyright 2015, American Physical Society. (h) Reproduced with permission from Ref. 98. Copyright 2017, American Chemical Society. (i) Reproduced with permission from Ref. 103. Copyright 2020, American Association for the Advancement of Science.]

Fig. 7. Ultrafast light-induced single-molecule dynamics. (a) Schematic representation of the experimental setup of combining THz pulses with a single C60 molecule transistor. (b) Interferogram of photocurrent of the C60 transistor. (c) Schematic representation of the energy band of phonon-assisted tunneling. (d) Schematic illustration of a single MgPc molecule adsorbed on the substrate. (e) Potential energy diagram of the single MgPc molecule. (f) Schematic diagram of coherent control of switching probability of single molecules through THz pulses. (g) Schematic representation of THz–STM experimental setup. (h) Asymmetric double-well potential exhibited by a single H2 molecule in STM. (i) THz rectification current of H2 molecules with the tip at different lateral positions. [(a)–(c) Reproduced with permission from Ref. 35. Copyright 2018, Springer Nature Limited. (d)–(f) Reproduced with permission from Ref. 125. Copyright 2020, Springer Nature Limited. (g)–(i) Reproduced with permission from Ref. 126. Copyright 2022, American Association for the Advancement of Science.]

Fig. 8. Ultrafast modulation of charge transfer. (a) Schematic illustration of the laser-induced tunneling current as a function of increasing laser intensity. (b) Schematic representation of electron tunneling driven by photons. (c) Schematic representation of electron tunneling driven by fields. (d) Schematic illustration of ultrafast electron tunneling through the HOMO. (e) Bias effect modulated by the THz pulses. (f) THz-induced imaging of the HOMO density contours. [(a)–(c) Reproduced with permission from Ref. 127. Copyright 2020, American Association for the Advancement of Science. (d)–(f) Reproduced with permission from Ref. 36. Copyright 2016, Springer Nature Limited.]