MKI80004 - Instrumentasi Kimia

Minggu Ke

Isi Pertemuan Keterangan

1 Uraian Perkuliahan: Isi Kuliah; Cara; dan EvaluasiPendahuluan/Introducton to Spectrometry

Lecturing & Discussion

2 Optical Spectroscopy and Instrumentation; UV-Vis [Absorption, Reflectance aspect] Spectrometry; Luminescence Spectroscopy

Lecturing & Discussion

3 Infra Red [Absorption Spectrometry, Reflectance aspect ] Spectrometry

Lecturing & Discussion

4 Introduction to Atomic SpectrometryAtomic Emission SpectroscopyAtomic Absorption Spectroscopy

Lecturing & Discussion

5 Atomic Spectrometry with X Ray:XRFXPS

Lecturing & Discussion

6

7 Class Discussion and Evaluation

8 Overview Other Instrumental Methods: Hyphenated Techniques Lecturing & Discussion

9 Topic of Choice I [1& 2] Active Learning

10 Topic of Choice II [1& 2] Active Learning

11 Topic of Choice III [1& 2] Active Learning

12 Topic of Choice IV [1& 2] Active Learning

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

Chromophore Example Excitation λmax, nm ε Solvent

C=C Ethene π  __>   π* 171 15,000 hexane

C≡C 1-Hexyne π  __>   π* 180 10,000 hexane

C=O Ethanaln  __>  π*π  __>  π*

290180

1510,000

hexanehexane

N=O Nitromethanen  __>  π*π  __>  π*

275200

175,000

ethanolethanol

C-X   X=Br      X=I

Methyl bromide

Methyl Iodide

n  __>  σ*n  __>  σ*

205255

200360

hexanehexane

Terminology for Asorption Shifts

Nature of ShiftDescriptive

Term

To Longer Wavelength

Bathochromic

To Shorter Wavelength

Hypsochromic

To Greater Absorbance

Hyperchromic

To Lower Absorbance

Hypochromic

                                                                                                                        

            

                                                      

                     

                                                   

                        

Empirical Rules for Absorption Wavelengths of Conjugated Systems

Woodward-Fieser Rules for Calculating the λmax of Conjugated Dienes and Polyenes

Core Chromophore Substituent and Influence

                                          Transoid Diene

215 nm

R- (Alkyl Group)   ....   +5 nmRO- (Alkoxy Group)   ..   +6 X- (Cl- or Br-)   .........   +10 RCO2- (Acyl Group)   ....   0

RS- (Sulfide Group)   ..   +30R2N- (Amino Group)   ..   +60

Further π -ConjugationC=C (Double Bond)   ...   +30C6H5 (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.

λmax (calculated) = Base (215 or 260) + Substituent Contributions

Some examples that illustrate these rules follow.

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 nmR = 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

                                 

Cyclopentenone202 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.

The Kubelka-Munk function, F(R), allows the optical absorbance of a sample to be approximated from its reflectance:

F(R)  =  (1-R)2

 2R

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