Table 1 Types of photothermal agents (PTAs) and their implications

Organic dye compounds

Indocyanine green (ICG)^117,118, Prussian blue^{119,120,121,122} IR dyes like BF₂^123,124, IR780, IR800, IR825, Porphysome¹²⁵

• Excellent PCE

• Thermostable

• Used for photoacoustic imaging purpose

• Photobleaching

• Instability

• Solvent toxicity

• Poor tumour targeting ability

Carbon nanomaterials

Carbon nanotubes^{126,127,128,129},Graphene and graphene oxide^130,131

• Excellent biocompatibility

• Better bioavailability

• Enhanced cargo-loading capacity

• Lower PCE

• Poor biodegradability

• Toxicity

• Complex synthesis methods

Metal-based agents

Zinc-based gold nanocomposite^132,133, Copper-based NPs^{132,134,135,136}, Gold nanostructures^137,138,139, Plasmonic gold nanostars^{139,140,141,142}, Plasmonic gold semi-shells¹⁴³, SPIONS^144,145

• Excellent PCE

• Easier surface modification

• Thermostable

• Non-toxic

• Enhanced specificity

• Stability concerns (potential for aggregation)

• Immunotoxicity

• Limited selectivity

Conjugate-based agents

Polypyrrole nanomaterials^146,147,

Conjugated polymers^30,46,148, Carbon-silica nanocomposites¹⁴⁹, Gold-decorated melanin nanoparticles¹¹⁸, Lanthanide ion-based up-conversion nanomaterial¹⁵⁰, Biomimetic gold nanoformulation¹⁵¹

• Enhanced PCE

• Increased tumour targeting and accumulation

• Multimodal imaging support

• Versatile surface modifications

• Often complex synthesis and characterization procedures

• Toxicity concerns

• Limited thermostability