MKI80004 - Instrumentasi Kimia Minggu Ke Isi Pertemuan Keterangan 1 Uraian Perkuliahan: Isi Kuliah; Cara; dan Evaluasi Pendahuluan/Introducton to Spectrometry Lecturing & Discussion 2 Optical Spectroscopy and Instrumentation; UV-Vis [Absorption, Reflectance aspect] Spectrometry; Luminescence Spectroscopy 3 Infra Red [Absorption Spectrometry, Reflectance aspect ] Spectrometry 4 Introduction to Atomic Spectrometry Atomic Emission Spectroscopy Atomic Absorption Spectroscopy 5 Atomic Spectrometry with X Ray: XRF XPS 6 7 Class Discussion and Evaluation 8 Overview Other Instrumental Methods: Hyphenated Techniques 9 Topic of Choice I [1& 2] Active Learning 10 Topic of Choice II [1& 2] 11 Topic of Choice III [1& 2] 12 Topic of Choice IV [1& 2] 13 Evaluation Short Talk 14 Final Evaluation

Cuvet

Violet:   400 - 420 nm Indigo:   420 - 440 nm Blue:   440 - 490 nm Green:   490 - 570 nm Yellow:   570 - 585 nm Orange:   585 - 620 nm Red:   620 - 780 nm

Methyl bromide Methyl Iodide Chromophore Example Excitation λmax, nm ε Solvent C=C Ethene π  __>   π* 171 15,000 hexane C≡C 1-Hexyne 180 10,000 C=O Ethanal n  __>  π* π  __>  π* 290 180 15 10,000 hexane hexane N=O Nitromethane 275 200 17 5,000 ethanol ethanol C-X   X=Br       X=I Methyl bromide Methyl Iodide n  __>  σ* n  __>  σ* 205 255 200 360

Nature of Shift Descriptive Term To Longer Wavelength Bathochromic To Shorter Wavelength Hypsochromic To Greater Absorbance Hyperchromic To Lower Absorbance Hypochromic Terminology for Asorption Shifts

                                                                                                                                    

                                                                           

Empirical Rules for Absorption Wavelengths of Conjugated Systems Core Chromophore Substituent and Influence                                            Transoid Diene 215 nm R- (Alkyl Group)   ....   +5 nm RO- (Alkoxy Group)   ..   +6 X- (Cl- or Br-)   .........   +10 RCO2- (Acyl Group)   ....   0 RS- (Sulfide Group)   ..   +30 R2N- (Amino Group)   ..   +60 Further π -Conjugation C=C (Double Bond)   ...   +30 C6H5 (Phenyl Group) ...   +60                                  Cyclohexadiene* 260 nm                       (i) Each exocyclic double bond adds 5 nm. In the example on the right, there are two exo-double bond components: one to ring A and the other to ring B. (ii) Solvent effects are minor. * When a homoannular (same ring) cyclohexadiene chromophore is present, a base value of 260 nm should be choosen. This includes the ring substituents. Rings of other size have a lesser influence. Empirical Rules for Absorption Wavelengths of Conjugated Systems Woodward-Fieser Rules for Calculating the λmax of Conjugated Dienes and Polyenes λmax (calculated) = Base (215 or 260) + Substituent Contributions

Some examples that illustrate these rules follow.

Woodward-Fieser Rules for Calculating the π __> π Woodward-Fieser Rules for Calculating the π __>  π* λmax of Conjugated Carbonyl Compounds Core Chromophore Substituent and Influence                                         R = Alkyl   215 nm R = H   210 nm R = OR'   195 nm α- Substituent   R- (Alkyl Group)   +10 nm   Cl- (Chloro Group)   +15   Br- (Chloro Group)   +25   HO- (Hydroxyl Group)   +35   RO- (Alkoxyl Group)   +35   RCO2- (Acyl Group)   +6 β- Substituent   R- (Alkyl Group)   +12 nm   Cl- (Chloro Group)   +12   Br- (Chloro Group)   +30   HO- (Hydroxyl Group)   +30   RO- (Alkoxyl Group)   +30   RCO2- (Acyl Group)   +6   RS- (Sulfide Group)   +85   R2N- (Amino Group)   +95 γ & δ- Substituents   R- (Alkyl Group)   +18 nm (both γ & δ)   HO- (Hydroxyl Group)   +50 nm (γ)   RO- (Alkoxyl Group)   +30 nm (γ) Further π -Conjugation  C=C (Double Bond)   ...   +30  C6H5 (Phenyl Group) ...   +60                                   Cyclopentenone 202 nm                                                                             (i) Each exocyclic double bond adds 5 nm. In the example on the right, there are two exo-double bond components: one to ring A and the other to ring B. (ii) Homoannular cyclohexadiene component adds +35 nm (ring atoms must be counted separately as substituents) (iii) Solvent Correction: water = –8; methanol/ethanol = 0; ether = +7; hexane/cyclohexane = +11 λmax (calculated) = Base + Substituent Contributions and Corrections

                                                                                                                                                                                                              Figure 1: Schematic diagram of UV-vis diffuse reflectance measurement system.

Figure 2: UV-vis diffuse reflectance spectrum for bulk Bi2O3. F(R) =  =  (1-R)2  2R The Kubelka-Munk function, F(R), allows the optical absorbance of a sample to be approximated from its reflectance: For a semiconductor sample this allows the construction of a Tauc Plot - (F(R).hv)n vs hv. For a direct band gap semiconductor the plot n = 1/2 will show a linear Tauc Region just above the optical absorption edge. Extrapolation of this line to the photon energy axis yields the semiconductor band gap- a key indicator of its light harvesting efficiency under solar illumination. Indirect band gap materials show a Tauc Region on the n = 2 plot.

                                                                                                                            Figure 3: Tauc Plot (n = 1/2) for bulk Bi2O3 after Finlayson et al. Phys. Stat. Sol.

Katalis Hasil Pengukuran Reflectant Acessories IR XRF dan XPS