Table 1.
Summary of the photonic crystal structures for chemical sensing presented in Section 3. The first column (left) indicates the dimensionality of the PhC, whereas the second column indicates the type of structure and its constituting materials. ∆λB is the value of the shift of the Bragg peak’s wavelength. When available, the value of the limit of detection (LOD) is reported.
| PhC | PhC Structure and Material | External Stimulus or Analyte Detected | Sensor’s Response | Ref. |
|---|---|---|---|---|
| 1D | Mesoporous layers of silica and titania | Hydrophobic and hydrophilic molecules | ∆λB = 47 nm for DHDP in THF | [35] |
| 1D | Hybrid silk-titanate layers | Humidity (RH) | ∆λB = 40 nm sensitivity (∆λ /∆RH%) = 0.28 | [36] |
| 1D | All-polymer Bragg multilayers (PPO, CA) | Volatile organic compounds | Chromatic discrimination of benzene, ODCB, CT, toluene | [37] |
| 1D | All-polymer Bragg multilayers (PS, CA) | Pollutants | LOD: MeOH (29 mg/L); EtOH (12 mg/L); 1 POH (12 mg/L); 2 POH (6 mg/L); BuOH (64 mg/L) | [38] |
| 2D | Composite Hydrogel (PS, poly HEMA-AA) | pH | ∆λB = 130 nm when pH goes from 2 to 8 | [40] |
| 2D | Composite hydrogel (Fe3O4 NPs embedded in PAM-PAA) | pH and ionic strength | ∆λB = 202 nm when pH goes from 2.02 to 7.03; ∆λB = 181 nm when NaCl varies from 0.02 M to 1 M |
[41] |
| 2D | Composite Hydrogel (PS, AM) | Urea and urease inhibitor | ∆λB = 28 nm when urea concentration varies from 1 to10 mM | [42] |
| 2D | Composite Hydrogel (PS, PAM-AA) | Organophosphate pesticide | LOD: 7.7 × 10−12 mmol/L for Dipterex | [43] |
| 3D | WO3 inverse opal | Acetone | LOD: 0.2 ppm | [45] |
| 3D | ZnO-Fe3O4 inverse opal | Acetone | LOD: 0.1 ppm | [46] |
| 3D | PEG inverse opal | Humidity | ∆λB = 40 nm when RH% goes from 30 to 90 | [48] |
| 3D | Composite direct opal based on PS and PDMS | Organic solvents | Chromatic discrimination of EtOH, MeOH, Silicone fluids | [49] |
| 3D | Composite direct opal based on PS and PDMS |
Butanol isomers | Chromatic discrimination of TerB, NB, 2B | [27] |
| 3D | Titanium oxide inverse opal | Ethanol solutions | Sensitivity = 9090 nm/RIU | [50] |
| 3D | MIP-hydrogel particles | MPA | Detection down to 1×10−6 M | [51] |
Abbreviations: DHDP: dihexadecyl phosphate; THF (solvent): tetra-hydrofuran; RH: relative humidity; PPO: poly(p-phenylene oxide); CA: cellulose acetate; ODCB: 1,2-dichlorobenzene; CT: carbon tetrachloride; PS: polystyrene; MeOH: methanol; EtOH: ethanol; 1 POH: 1-propanol; 2 POH: 2-propanol; BuOH: 1-butanol; HEMA: 2-hydroxethyl methacrylate; AA: acrylic acid; NP: nanoparticle; PAM: poly(acrylamide); PAA: poly(acrylic acid); AM: acrylamide; PEG: polyethylene glycol; PDMS: polydimethylsiloxane; TerB: 2-methylpropan-2-ol, NB: butan-1-ol; 2B: butan-2-ol; MIP: molecularly imprinted polymer; MPA: methanephosphonic acid.