Question

Choose the correct statements
• Nanomaterials show tunable band gap energies
• Nanomaterials offers enhanced catalytic properties compared to their bulk counterparts
• Nanomaterials have fixed band gap energies
• At nanoscale, color will tell you the size or vice-versa Choose the correct answer from the options given below:
• A, B, C & D Only
• A, B, & D Only
• B, C & D Only
• A & D Only

• A. A, B, C & D Only
• B. A, B, & D Only
• C. B, C & D Only
• D. A & D Only

Hint:

Important properties of nanomaterials:
• Tunable band gap
• Size-dependent color
• Enhanced catalytic activity
• Large surface area

Answer 1

The Correct Option is B

Concept: Nanomaterials are materials having dimensions approximately in the range: \[ 1\text{ nm to }100\text{ nm} \] At nanoscale dimensions, materials exhibit unusual properties because of:
• Quantum confinement effects
• Large surface area to volume ratio
• Increased surface atoms These effects significantly alter:
• Optical properties
• Electrical properties
• Catalytic properties
• Magnetic properties

Step 1: Examine Statement A carefully. Statement A says: “Nanomaterials show tunable band gap energies.” This statement is correct. At nanoscale:
• Electronic energy levels change with particle size.
• Quantum confinement becomes important. Thus, band gap energy changes with nanoparticle size. Smaller nanoparticles generally possess: \[ \boxed{ \text{Larger band gap} } \] Hence, nanomaterials indeed show tunable band gap energies. Therefore, Statement A is correct.

Step 2: Examine Statement B carefully. Statement B says: “Nanomaterials offer enhanced catalytic properties compared to their bulk counterparts.” This statement is also correct. Reason:
• Nanoparticles possess enormous surface area.
• More atoms remain exposed on the surface.
• Surface atoms participate actively in catalysis. Therefore catalytic efficiency increases significantly. Hence, Statement B is correct.

Step 3: Examine Statement C carefully. Statement C says: “Nanomaterials have fixed band gap energies.” This statement is incorrect. Band gap energies in nanomaterials are not fixed. They vary with:
• Particle size
• Shape
• Composition This tunability is one of the most important properties of nanomaterials. Thus Statement C is false.

Step 4: Examine Statement D carefully. Statement D says: “At nanoscale, color will tell you the size or vice-versa.” This statement is correct. Nanoparticles exhibit size-dependent optical properties. For example:
• Gold nanoparticles show different colors for different sizes.
• Quantum dots emit different colors depending upon size. Thus: \[ \boxed{ \text{Color and size are related at nanoscale} } \] Hence Statement D is correct.

Step 5: Identify correct statements. We found:
• A is correct
• B is correct
• C is incorrect
• D is correct Therefore: \[ \boxed{ A,\ B,\ \&\ D\ \text{Only} } \]

Step 6: Match with the options. The correct option is: \[ \boxed{(2)} \] Additional Understanding: Nanotechnology applications include:
• Drug delivery
• Solar cells
• Sensors
• Catalysts
• Quantum dots The tunable optical and electronic properties make nanomaterials technologically very important. Final Conclusion: Correct statements are: \[ \boxed{ A,\ B,\ \&\ D\ \text{Only} } \] Hence, the correct answer is: \[ \boxed{(2)} \]