Teeth discoloration is mainly treated with dental bleaching. Use of chemical bleaching has side effects, so it is important to find an alternative natural dental bleaching agent. Averrhoa bilimbi contains peroxide and oxalate acid that possess tooth whitening properties. Objective: To determine the change in color of dental enamel after the application of Averrhoa bilimbi and 10% carbamide peroxide. Methods: Samples were 20 post-extracted of the two tested materials premolars (10 specimens each for Averrhoa bilimbi and carbamide peroxide application). After the application, the specimens were incubated at 37ºC for 2 hours, washed and soaked in aquadest before further incubated for another 14 days. The colour changed was observed by 5 independent observers using shade guide. Results: Quantitative and qualitative analyzes were performed. Qualitatively, A3 color has changed into C1, A2, D2, B2 and B1 in the Averrhoa bilimbi group. A more significant color change in the 10% carbamide peroxide group (p=0.005) compared to Averrhoa bilimbi group (p=0.005) were observed. The difference of resulted enamel colour change was statistically significant (p=0.002). Conclusion: Averrhoa bilimbi had a good prospect as dental bleaching agent since its application effectively resulted in a slight enamel colour change although its whitening properties was still lower than 10% carbamide peroxide. ABSTRAKPerubahan warna email setelah aplikasi Averrhoa bilimbi. Perubahan warna gigi terutama diatasi dengan melakukan perawatan pemutihan gigi. Penggunaan agen pemutih kimia dapat menyebabkan efek samping, sehingga perlu ditemukan agen pemutih gigi alternatif berbahan dasar alam. Averrhoa bilimbi mengandung peroksida dan asam oksalat yang memiliki kemampuan memutihkan gigi. Tujuan: Menganalisis perubahan warna email gigi setelah aplikasi Averrhoa bilimbi dan karbamid peroksida 10%. Metode: Penelitian ini menggunakan 20 gigi premolar pascaekstraksi (masing-masing 10 spesimen untuk aplikasi Averrhoa bilimbi dan karbamid peroksida 10%). Setelah aplikasi, spesimen diletakkan di inkubator 37°C selama 2 jam, kemudian dicuci dan direndam dalam akuades, dan diinkubasi kembali selama 14 hari. Perubahan warna diamati oleh 5 pengamat menggunakan panduan warna. Hasil: Hasil pengamatan dianalisis secara kualitatif dan kuantitatif. Perubahan warna email gigi setelah aplikasi dengan Averrhoa bilimbi dari A3 menjadi C1, A2, D2, B2, dan B1. Perubahan warna gigi secara homogen dari A3 ke B1 terjadi dalam aplikasi karbamid peroksida 10%. Perubahan warna yang lebih jelas terjadi pada kelompok karbamid peroksida 10% (p=0,004) dibandingkan kelompok Averrhoa bilimbi (p=0,005). Perbedaan perubahan warna yang terjadi pada kedua kelompok tersebut berbeda bermakna (p=0,002). Simpulan: Averrhoa bilimbi memiliki prospek yang baik sebagai bahan pemutih gigi karena penggunaannya dapat menimbulkan perubahan warna email, namun efektivitasnya masih di bawah 10% karbamid peroksida.

Mono- and bis-rhodamine derivatives appended with amino (RhB1) and imino (BRI) groups, respectively, have been designed as colorimetric and fluorescent sensors for the selective detection of Pd. In addition, an attempt has been made to improve the water solubility of the probe by synthesizing inclusion complexes of RhB1 with β-cyclodextrin as the host molecule. The resulting probe, RhB1-CD, exhibited exactly the same physicochemical phenomena as the guest molecule RhB1, indicating that complexation with β-CD improved the water solubility of RhB1 without affecting its sensing ability. With increasing concentrations of Pd, the absorption (556 nm) and emission (591 nm) intensities of BRI as well as the absorption intensities of RhB1/RhB1-CD (563 nm) increase, whereas the emission intensities of RhB1/RhB1-CD decrease due to fluorescence quenching. Therefore, BRI can act as an "OFF-ON" fluorescent probe switch in CHCN/HO (3 : 2 v/v) with a detection limit of 1 μM in solution, whereas RhB1 and RhB1-CD act as "ON-OFF" fluorescent probes in EtOH/HO (1 : 1 v/v) and water, respectively, with a detection limit of 10 μM. All these probes exhibited high selectivity for Pd and reversibility by treatment with NaS. In the presence of commonly coexisting metal ions, such as Hg, Fe, Cu and Al, BRI undergoes either catalytic Schiff base hydrolysis or it is unaffected by its affinity to the metal ions. However, Pd can be effectively distinguished by a 12-15 nm bathochromic shift in its emission spectrum when compared with that of other metal ions. A Job's plot revealed that BRI forms 1 : 2 complexes by a spirolactam ring opening mechanism, whereas RhB1/RhB1-CD form 2 : 1 complexes by a ring opening mechanism followed by Pd-induced dimerization; the proposed binding mechanisms are presented.

Azobenzene and cholesteryl based derivatives (N2 and N4) were designed as gelators and their aggregation mechanism is proposed. These gelators are thermally reversible, however optically irreversible.

A new series of symmetric, bis-cholesteryl-appended, isosorbide derivatives (BCIE, BCIC2 and BCIC4) were designed as gelators to respond to changes in their environment and were synthesized successfully. Among these derivatives, BCIE can gel a wide variety of organic solvents (23 solvents), suggesting that BCIE acts as a more versatile gelator than BCIC2 and BCIC4. The CGC of the gels varies from 1.53 mM in 1-hexanol to 23 mM in pyridine. The results of the gelation ability in different solvents revealed that changing the linking group (ester/carbamate) attached to the cholesteryl units can produce a dramatic change in the gelation behavior of the compounds. The morphology of the as-formed organogels can be regulated by changing the types of organic solvents. The results from electron microscopy studies revealed that the gelator molecule self-assembled into different aggregates, from wrinkled fibers to dense fibers, with the change of solvents. The gels of BCIE in 1-hexanol and 1-octanol exhibited strong CD (circular dichroism) signals, indicating that the gelation induced supramolecular chirality in these gel systems. Secondary forces of van der Waals and π-π stacking (from both 1,2,3-triazole and aromatic units) played important roles in the aggregation of compounds in the solvents according to FTIR and variable temperature (1)H-NMR analysis, and a mechanism for the gel formation was proposed. The gel-to-sol phase transition can be triggered by the addition of trifluoroacetic acid (TFA), and the gel state was obtained slowly (after 1 day) when neutralizing with triethyl amine (TEA), which indicated that the sol ⇄ gel phase transitions are tunable by pH, which is further supported by (1)H-NMR and SEM analysis. In addition, the gel stability of BCIE was investigated using Cu(2+), Cd(2+), Ag(2+), Fe(3+), Hg(2+), Mg(2+), Pd(2+), Al(3+) and Zn(2+), and the results showed that the gel-to-sol phase transition process could be selectively controlled by interaction with Pd(2+) and Zn(2+) because complexation with 1,2,3-triazoles destroyed the interactions between the triazoles, collapsing the gel, which was further evidenced by (1)H-NMR and SEM analysis. However, the gel stability of BCIE was enhanced by the addition of Pd(2+) and Zn(2+) in the presence of pyridine, whereas the gel collapsed in other solvents, which may be due to the chelating effect of the pyridine moiety. Another interesting feature of this gel is that when using the gelator as a stabilizer, stable water in oil (W/O) gel-emulsions were created, in which styrene can be used as the continuous phase and water as the dispersed phase with the stabilizer in the continuous phase of only 2% (w/v). Gel-emulsions were observed with any ratio of water to styrene.